Long-runout landslides are well-known and notorious geologic hazards in many mountainous parts of the world. Commonly encompassing enormous volumes of debris, these rapid mass movements place populations at risk through both direct impacts and indirect hazards, such as downstream flooding. Despite their evident risks, the mechanics of these large-scale landslides remain both enigmatic and controversial. In this work, we illuminate the inner workings of one exceptionally well-exposed and well-preserved long-runout landslide of late Pleistocene age located in Eureka Valley, east-central California, Death Valley National Park. The landslide originated in the detachment of more than 5 million m3 of Cambrian bedrock from a rugged northwest-facing outcrop in the northern Last Chance Range. Its relatively compact scale, well-preserved morphology, varied lithologic composition, and strategic dissection by erosional processes render it an exceptional laboratory for the study of the long-runout phenomenon in a dry environment. The landslide in Eureka Valley resembles, in miniature, morphologically similar “Blackhawk-like” landslides on Earth, Mars, and minor planet Ceres, including the well-known but much larger Blackhawk landslide of southern California. Like these other landslides, the landslide in Eureka Valley consists of a lobate, distally raised main lobe bounded by raised lateral levees. Like other terrestrial examples, it is principally composed of pervasively fractured, clast-supported breccia. Based on the geologic characteristics of the landslide and its inferred kinematics, a two-part emplacement mechanism is advanced: (1) a clast-breakage mechanism (cataclasis) active in the bedrock canyon areas and (2) sliding on a substrate of saturated sediments encountered and liquefied by the main lobe of the landslide as it exited the main source canyon. Mechanisms previously hypothesized to explain the high-speed runout and morphology of the landslide and its Blackhawk-like analogs are demonstrably inconsistent with the geology, geomorphology, and mineralogy of the subject deposit and its depositional environment.Long-runout landslides are notable geologic hazards in many mountainous regions of the world, including large portions of North and South America, Europe, and Asia. Risks include direct impacts to population centers and infrastructure by the highly mobile debris [1–3], downstream inundation hazards resulting from emplacement of debris into standing bodies of water [4], and the creation and failure of landslide dams [5]. In addition to the physical hazards represented by landslide dams, they also have the potential to impound large volumes of water in remote areas, affecting water quality and availability in downstream areas [6]. We anticipate that these hazards will only increase over time in response to population pressures and infrastructure growth in and downstream from mountainous regions.Despite these evident hazards, which cost the lives tens of thousands of individuals in the twentieth century alone, the mechanics of long-runout landslides remain enigmatic and controversial. The present work seeks to illuminate the inner workings of one exceptionally well-exposed and well-constrained long-runout landslide for application to the larger class of such features worldwide, with the joint goals of better constraining the hazards represented by these major landslides and developing a better understanding of the role of environmental factors in promoting their long-runout behavior.The Eureka Valley landslide lies immediately southeast of the Eureka Dunes at the southern end of the Eureka Valley, east-central California, Death Valley National Park, at latitude 37° 04′ 27″ N, longitude 117° 38′ 49″ W (Figure 1). The landslide originated from a rugged northwest-facing outcrop of Cambrian limestone and sedimentary strata in the central Last Chance Range in late Pleistocene time. We adopt the informal name Eureka Valley landslide (hereinafter EVL) for the feature following McKeown and Bishop [7], who initially described it. Watkins [8] provided a minimum age estimate of 8.3-9.4 ka for the deposit based on Optically Stimulated Luminescence methods and proposed a clay lubrication and/or subaqueous emplacement mechanism to explain its long-distance transport.The EVL exhibits in relatively compact form numerous characteristic features of long-runout landslides in general and “Blackhawk-like” landslides in particular. Shaller [9] defined Blackhawk-like landslides as a subgroup of morphologically simple, dry rock long-runout landslides that resemble the well-known Blackhawk landslide of southern California [10]. Other terrestrial examples include the Silver Reef landslide of southern California [10], the New York Butte landslide in nearby Owens Valley, California [11], and a cluster of similar deposits documented in western Argentina [12]. Blackhawk-like landslides also occur on Mars [9] and dwarf planet Ceres (Figure 2).We apply the term “long-runout landslide” herein in lieu of the terms “sturzstrom,” “rock avalanche,” and “rockslide avalanche,” which are other frequently applied terms for such rapid, large-scale mass movements, to avoid the mechanistic associations implied by their usage. Also, avoided is the older term “megabreccia” from basin analysis, though these notable sedimentary deposits frequently represent the remains of ancient long-runout landslide deposits.Hsü [2] defined long-runout landslides as those having fall height (vertical distance from crown to toe, H) to travel length (horizontal distance between crown and toe, L) ratios of less than 0.6. Hsü [2] named this ratio the “fahrböschung” following Heim [16], which is literally translated from the original German as “travel slope.” Heim [16] also referred to this measure as the “energy line.”A better understanding of the EVL is important for a variety of reasons. Principally, the deposit provides valuable insights into the elusive transport mechanism(s) responsible for the long runout and other characteristics of rapid, large-scale landslides, a matter of considerable debate for over a century [17]. A better understanding of this fundamental geologic process is essential to improving landslide hazard risk assessments in mountainous terrain. Another valuable product of this study is a better understanding of the sedimentology of these deposits, which play a major role as petroleum reservoirs in the Basin and Range region of the western United States [18, 19]. This study also provides new insights into the geology of the local area, including availability of surface water and the depth to groundwater during a recent glacial/pluvial episode. Finally, an improved understanding of the EVL and its morphological analogs has the reach goal of utilizing landslide morphology to remotely gage the past and present availability of liquid water on the surface of other planetary bodies, particularly Mars [9, 20].The EVL consists of three principal components (Figure 1): a prominent main lobe (hereinafter ML) located on the alluvial piedmont below the mountain front, a pair of “minor lobes” (irregularly shaped accumulations of limestone breccia) located on ridges and canyons southeast of the ML, and another pair of minor lobes located northwest of the ML runout track. The ML itself consists of two principal components: a teardrop-shaped “distal heap” (hereinafter DH) and a raised lateral levee bounding the southern edge of its runout track. Based on comparison with morphologically similar landslides elsewhere (Figure 2), a similar levee is assumed to have originally bounded the northern side of the deposit that has since succumbed to erosion.The EVL appears on the 1 : 62,500 scale Last Chance Quadrangle geologic map of Wrucke and Corbett [13]. The deposit lies along the northwestern margin of the northeast-striking Last Chance Range, which exposes a layered sequence of Cambrian-age siltstone, sandstone, quartzite, and carbonate sedimentary strata (Figure 1). From oldest to youngest, these include the Early Cambrian Wood Canyon Formation, the Early to Middle Cambrian Zabriskie Quartzite, the Middle Cambrian Carrara Formation, and the Middle to Late Cambrian Bonanza King Formation. Except where deformed along the range-bounding frontal fault, these deposits locally exhibit moderate southeasterly (into-slope) dips.The range front is bounded by late Quaternary normal faults [21], including a pair of northeast-trending fault scarps that offset the landslide and adjacent alluvial surfaces. Profiles of the two normal fault scarps are consistent with Mw 7.1 to 7.3 events for the scarp-forming earthquakes [22]. The Mw 6.1 Big Pine earthquake, which struck near the western side of the valley on May 17, 1993, represents the largest historical seismic event recorded in Eureka Valley. This earthquake was associated with a series of small surface ruptures in the central part of the valley 6 to 21 km northwest of the landslide but no additional scarps in the vicinity of the landslide [14, 23].In addition to seismic events of local origin, the Eureka Valley is subject to ground shaking from more distant earthquake sources [23], including the Death Valley (13 km northeast) and Owens Valley Fault Zones (53 km southwest). The latter is associated with the 1872 Lone Pine earthquake, California’s largest historical seismic event, estimated to have produced approximately level VIII ground shaking in the Eureka Valley [24].The EVL is derived principally from bedrock of the Carrara and Bonanza King Formations. The Carrara Formation locally consists of yellowish-brown, brown, and grayish-brown interbedded limestone, silty limestone, siltstone, sandstone, and shale. The Bonanza King Formation consists of black dolomitic limestone with occasional bands of white limestone.The EVL originated on a steep northwest-facing slope in the upper reaches of the unnamed “main source canyon” (hereinafter MSC), a 341 ha watershed exhibiting approximately 1,040 m of vertical relief and a peak elevation of approximately 2,130 m. The unnamed adjacent southerly watershed contains the principal minor lobe (hereinafter PML). It is a 36 ha watershed with approximately 415 m of vertical relief and a peak elevation of about 1,550 m. Other nearby watersheds affect the EVL by way of their associated alluvial fans, which are labeled on Figure 1. Table 1 summarizes the key characteristics of these watersheds.Schlom and Knott [14] mapped the EVL and nearby alluvial fan surfaces (Figure 1). Alluvium overlying the proximal portion of the landslide today stands as much as 25 m above the active channel draining the MSC. The alluvium has an exposed thickness of up to 6 m and locally exhibits a well-developed desert pavement, pitted carbonate clasts, and dark brown varnish on noncarbonate clasts. These characteristics resemble alluvial surfaces in nearby Death Valley dated to 60-80 ka [25].The 25 m of fan head incision that followed deposition of the proximal alluvial fans represents, in part, a return to predisturbance watershed characteristics. Other geomorphic evidence in the vicinity suggests, however, that the incision observed at the mouth of the MSC includes the effects of tectonic- and/or climate-related processes unrelated to the landslide [26]. This evidence includes ~2 to 5 m of fan head erosion and ~1 to 2 m alluvial fan incision along nearby portions of the range front. The southerly margin of the ML is also experiencing active erosion, as are the margins of the dune-clad alluvial deposit to the northwest (Figure 1, unit Qo?). Potential underlying causes of this widespread erosional activity includes the declining activity of the range-bounding normal faults and/or a reduction in debris production associated with the shift from Pleistocene to Holocene climate conditions.Other notable and relevant geologic features present in the vicinity of the EVL include (see Figure 1 for feature locations):Feature 1: a ridgetop fissure (sackung) located above and to the north of the landslide source areaFeature 2: a large talus accumulation occupying the headscarp bowl vacated by the landslideFeature 3: a small body of playa sediments located near the wind gap at the head of the PMLFeature 4: an erosionally sculpted arch of landslide debris that exposes the base of the PMLFeature 5: a small playa located along the upslope edge of the DHFeature 6: the eroded lateral margin of a possible outwash lobe mantled by drift sand and a veneer of rhyolite clasts derived from Dedeckera CanyonFeature 7: intermittent exposures of the main frontal fault with mullion structure, drag folding, and light-colored travertine depositsFeature 8: an isolated mass of Carrara and Bonanza King landslide breccia in preserved stratigraphic sequence with clastic dike and probable reworked travertine depositsFeature 9: a small lobe of Carrara limestone breccia that overtopped the northern edge of the source watershed at approximately elevation 1,295 m, corresponding with the westerly limit of an erosional trim lineFeature 10: a series of locally reworked outcrops of Carrara limestone breccia that represent erosional remnants of a once extensive body of breccia deposited located near the mouth of the MSCFeature 11: an erosional “trim line” roughly 50-100 m above the canyon floor that apparently formed by scour from passing landslide debris; the trim line is visible in Google Earth imagery running about 700 m along the north side of the MSCThese features were field verified where feasible except for Features 1, 2, and 11, which were interpreted solely from Google Earth imagery and/or remote field observation.Tables 2–5 summarize the key physical characteristics of the EVL. Except where noted, all elevations, distances, and area measurements rely on Google Earth topography. Many of the morphological and textural characteristics of the EVL resemble features exposed on other long-runout landslide deposits. Table 2 lists these features along with their relative prevalence elsewhere [9].As noted, the EVL consists of the prominent main lobe and a series of minor lobes. The initial separation of the slidemass into distinct lobes occurred when the speeding mass encountered a bedrock ridge lying across its path in the upper reaches of the MSC. Roughly 60% of the debris passed to the right (north) of this ridge and traveled downhill to form the ML and the northerly minor lobes; the remaining 40% passed to the left (south), forming the PML and a small subsidiary lobe. The irregular shapes of the various minor lobes result from their originally sinuous travel paths combined with postemplacement erosion.Debris that formed the ML remained channelized for the first ~1,500 m of its downhill run, emerging from the mouth of the MSC with a width of about 300 m and a thickness in excess of about 15 m, based on the geometry of the canyon and the height of the levee at its mouth (Figure 1, Profiles E and F). It thereafter experienced considerable spreading and thickening as it descended the alluvial fan below the mouth of the canyon. From an initial width of ~300 m, the ML expanded to a width of ~400 m by the conclusion of movement (i.e., a 133% increase) and experienced as much as 20 m of distal thickening.The ML’s distinctive south lateral levee, despite appearances, is not a simple constructional landform akin to a mudflow levee. Rather, its inner edge typically averages about 10 m lower than its corresponding outer margin based on five Google Earth topographic profiles (Figure 1, Transects A-F), confirmed with field measurements of Transects A-C using a Ziplevel® electronic water level. These observations imply that the ML eroded its bed during emplacement, incorporating as much as 1.6 million m3 of substrate material as it descended the alluvial fan (corresponding to 10 m of scour over the 16 ha area bounded by the levees, mountain front, and distal heap). This implied volume neatly balances the volume represented by the widening and thickening of the ML.Table 5 summarizes the area and volume of the EVL and its major components, including the effects of alluvial scour and a bulking factor of 25% for the conversion of intact rock to breccia [27]. As indicated, the estimated total volume of intact limestone represented by the various lobes of the EVL ranges from 4.2 to 5.5 million m3 depending on the extent of basal scour that accompanied emplacement of the ML.The ML consists principally of clast-supported, angular to subrounded breccia that exhibits crude reverse grading, as represented by numerous large isolated boulders that litter the surface of the deposit. Grain sizes vary widely, ranging from silt- or clay-sized rock flour up to boulders several meters in diameter. In several locations, the slide debris is pervasively fractured but minimally disarticulated, a texture referred to elsewhere as three-dimensional jigsaw puzzle breccia [10]. At a finer scale, crude color banding, often of subhorizontal orientation, is common. Abrupt grain size and other textural changes, the occasional appearance of gouge-like material, and the presence of contorted bedding adjacent suggest that these features represent internal shear zones. On the northern side of the DH (Figure 1, Location Y), one of these shear features steepens dramatically to an angle of 56° (dip to southeast, upslope) giving the appearance of reverse faulting.At outcrop scale, the eroded southern edge of the ML offers a spectacular example of preserved headscarp stratigraphy. Here, the basal two-thirds of the exposure consists of brown to yellow-brown Carrara Formation breccia, the upper third of gray, white, and black Bonanza King Formation breccia. The latter includes a distinctive, distended white marker bed, as well as most of the boulders that project above the surface of the deposit. These disarticulated bedrock units are radically attenuated relative to their intact geometry on the slope but otherwise preserve their original stratigraphic sequence and relative thicknesses with little intermixing. Comparison of color band thicknesses at Location X (Figure 1) with the intact correlative bands on the slope yields an attenuation ratio of approximately 40 : 1 for the displaced material (Table 6). Based on comparison with the bedrock relations exposed in the headscarp bowl, this attenuation ratio implies that the base of the landslide likely lies less than a meter below the base of the exposure.The more extensively eroded northern side of the ML exposes a more complex array of textures and structures. Near the mouth of the MSC, the breccia overrides a bedrock ridge in the Wood Canyon Formation, then cuts obliquely across the original alluvial surface (Figure 1, Location Z). Outcrops in this area expose gray to white limestone breccia overlying limestone-dominated alluvium containing a minor admixture of other rock types. Similarities in color and texture between the breccia and the underlying alluvium render these units comparatively difficult to distinguish in many field exposures, and much of the exposed material may represent comingled or interfingering deposits of the two materials [28]. Locally, however, the landslide-alluvium contact is readily identified. At one such location, the contact is marked by a 30 cm thick, matrix-supported, normally graded, silty sand with gravel interval. Larger gravel and cobbles appear to have settled to the bottom of this layer, and its upper surface interfingers with the overlying landslide breccia. Overall, the texture is suggestive of a fluidized boundary layer between the landslide and the alluvial substrate.Unlike the ML, the PML consists almost entirely of brown to yellow-brown Carrara limestone breccia. A veneer of gray limestone breccia caps many outcrops, however, suggesting another instance of preserved headscarp stratigraphy, with Bonanza King breccia overlying Carrara Formation-derived material. As in the ML, subhorizontal internal slip surfaces are common, often juxtaposing breccia of contrasting color and texture. Locally, bands of uniformly colored and textured breccia are deformed into arches and chevron folds with wavelengths and amplitudes ranging from roughly 2 to 10 m.At one location at the base of an erosionally sculpted arch (Figure 1, Feature 4), an approximately 10 cm thick boundary layer lies sandwiched between intact bedrock below and breccia of contrasting texture and color above. This layer is composed mainly of poorly sorted sand- and gravel-sized limestone breccia (Table 7) and is traceable laterally to a point where it departs from the bedrock surface and intrudes into the overlying slidemass. The results of an XRD analysis of material collected from the boundary layer confirm the dominant carbonate lithology of the landslide and the extremely low concentration of clay minerals contained therein (Table 7).Nearby, a local depression in the bedrock contains up to 30 cm of angular gravel and cobbles, which in turn is overlain by finer breccia. We interpret these relations to represent localized deposition from the coarse-grained leading edge of the landslide, which filled low spots in the topography as it descended the slope. Similar relations exist at the base of the Martinez Mountain rock avalanche of southern California, where they are present at a much larger scale [9, 29].Local exposures of the PML exhibit sufficient fines content to develop a matrix-supported texture. Small-scale levees occur along the margins of the deposit in this general area that resemble those commonly bounding mudflow deposits [30]. Despite the presence of these locally fluid-appearing textures and features, the dominant clast-supported texture of the landslide is quite distinct from a typical debris flow deposit.Isolated masses of landslide breccia overtopped the northerly drainage divide near the mouth of the MSC and came to rest on the slopes of adjacent northerly canyons (Figure 1, Locations 8 and 9). At Location 8, a body of landslide breccia about 10 m thick drapes over the ridge dividing the watersheds. This exposure consists mainly of Carrara Formation breccia, capped by blocks of black Bonanza King limestone, representing a third example of preserved stratigraphic sequence in the landslide mass. Blocks of Carrara and Bonanza King limestone exposed near the summit of this side lobe exhibit three-dimensional jigsaw puzzle texture, as observed elsewhere on the landslide, along with cavernous weathering.The base of the landslide is well exposed in the vicinity of Location 8 for tens of meters along its contact with the underlying Wood Canyon Formation. At this location, locally derived Wood Canyon clasts form a substantial admixture to the predominantly Carrara-derived landslide breccia, indicating substantial local scour of the bedrock surface. Nearby, a light brown to white matrix infiltrates the landslide breccia along the contact and extends into the body of the deposit. This pale colored matrix, unique among exposures of the landslide, suggests the probable local incorporation of frontal fault-associated travertine deposits during runout. This material appears to have intruded the fractured surface of the underlying bedrock, loosening and detaching angular slabs of rock via a stoping-type mechanism. Similar material can be observed nearby mixing into the body of the debris, as well as forming a clastic dike that intrudes a block of black Bonanza King limestone near the summit of the deposit, approximately 10 vertical meters above the base.An isolated mass of Carrara Formation breccia occurs at Location 9, where it overtopped the drainage divide from the MSC and cascaded down a steep north-facing slope. The resulting deposit is a disorganized mass of gravel, cobbles, and boulders.A series of factors set the stage for the EVL slope failure. Quaternary uplift along the Eureka Valley Fault Zone produced the requisite uplift and resulting steep relief along this portion of the mountain front, accompanied by differential weathering between the Carrara and Bonanza King Formations. As is common for these units in the Death Valley area, the siliceous Carrara limestone is a slope former, whereas the overlying Bonanza King limestone and dolomite is a cliff-forming unit [31]. On this basis, we hypothesize that a protracted period of preferential weathering of the Carrara Formation resulted in progressive erosional undercutting of the Bonanza King Formation in the source area of the EVL in advance of the slope failure.Intersecting, valley-dipping, moderately to steeply inclined joint sets within the Bonanza King Formation further reduced the stability of the oversteepened slope. Based on Google Earth imagery, these joint sets appear to control the geometries of large planar slope areas above the talus accumulation in the source area. Figure 1 shows the estimated orientations of these joint sets, calculated by application of three-point geometry methods. The sheer slopes and active tectonic environment contributed to the formation of an apparent sackung feature on the ridgeline northeast of the headscarp bowl that projects towards the head of the landslide (Figure 1, Feature 1). Sackung features form in response to gravitational spreading of ridgelines due to a loss of lateral support (typically in glaciated terrains) or due to intermittent movement in response to seismic ground accelerations [32]. This observation suggests that some of the joint surfaces in the headscarp vicinity have experienced a protracted history of differential movements.Comparison of the bedrock stratigraphy with the stratigraphy exposed in the ML indicates the highest portion of the scarp preserved in the final deposit is a prominent white limestone marker bed that outcrops at the edge of the talus-mantled headscarp bowl that is projected to lie at around elevation 1,737 m within the bowl. The slope length between the marker bed and base of the headscarp bowl at around elevation 1,545 m is approximately 386 m. Given that the headscarp bowl is approximately 300 m wide, we calculate that the portion of the slide block preserved in the final deposit originally measured approximately 300 m wide by 386 m long (parallel to slope) by 35 to 47 m thick (normal to slope). The lower thickness estimate corresponds to the case of maximum ML alluvial scour; the greater thickness applies to the nonscour case.The geomorphology of the headscarp bowl implies that the original slope failure contained more material than is accounted for by the existing landslide deposits. This missing material consists of Bonanza King bedrock originally present in the slope area above the white marker bed, extending upslope to the crown of a fresh-appearing planar scarp at about 1,900 m. A distinct break in slope and color change marks the top of this scarp, which is located approximately 50 m below the ridge line; above this limit, the rock mass is darker and more heavily weathered. Some of the rock encompassed in the slope failure remained in the headscarp bowl to form the prominent talus deposit present therein, but the majority exited the headscarp and was presumably deposited in the MSC.Table 8 provides the estimated elevations, dimensions, and volumes of rock displaced from the headscarp bowl during the EVL. It also provides an estimate of the volume of debris that still resides in the headscarp bowl as talus (approximately 0.5 million m3). Postlandslide erosion of a steep-walled watershed at the head of the scarp produced roughly 0.05 million m3 about one-tenth of this total. The remaining 0.45 million m3 consists of material derived from the original slope failure that remained in the headscarp bowl after the failure. This accounting raises our estimate of the volume of the initial slope failure to between 4.9 and 6.6 million m3 but yields a “missing” volume of approximately 0.8 to 1.2 million m3 that is neither accounted for by the talus or by our current accounting of landslide debris. We evaluate the implications and disposition of this additional displaced material in the subsequent discussion.The triggering event for the landslide is unknown. The proximity of the EVL to active Quaternary faults makes a plausible, though controvertible, case for seismic triggering of the landslide. Rainfall in Eureka Valley is sparse, with rainfall totals between 2013 and 2019 averaging only 62 mm/yr. [33] Much of the annual precipitation today occurs during winter and likely falls as snow on the higher surrounding peaks. Even during late Pleistocene time, average yearly precipitation likely did not exceed twice the modern value [34, 35]. Because snow accumulation was likely significant at higher elevations in late Pleistocene time, frost wedging represents a potential additional contributing factor to the slope failure. Given the extremely steep topography in the source area, accumulation of direct rainfall or elevation of a groundwater table in the ridge both seem unlikely factors in triggering the landslide, but the steep terrain could contribute to slope creep (likely focused along on preexisting discontinuities), a phenomenon that has been known to accelerate into large-scale slope failure of this magnitude [9, 16].The emplacement of the EVL affected runoff and sediment production from several contiguous watersheds along the range front (Figure 1, Table 1), which, in turn, modified the geomorphology of the landslide. These modifications have altered the deposit morphology sufficiently to require separate treatment of the evolution of the local watersheds and their associated alluvial fans. These relevant watersheds include: (1)The MSC, in which the landslide originated(2)The adjacent unnamed “north” watershed which hosts two minor debris lobes of landslide debris(3)The adjacent unnamed watershed immediately south of the MSC that hosts the PML and whose alluvial fan (shaded green in Figure 1) abuts proximal sections of the main lobe’s intact southerly levee(4)The “south” watershed, located adjacent to the PML-hosting watershed and north of much larger Dedeckera Canyon. The alluvial fan associated with this small canyon (shaded blue in Figure 1) abuts and is actively eroding the central reach of the intact lateral levee(5)The large Dedeckera Canyon watershed (shaded pink in Figure 1), whose associated alluvial fan abuts the toe and distal portions of the MLThe MSC, in which the landslide originatedThe adjacent unnamed “north” watershed which hosts two minor debris lobes of landslide debrisThe adjacent unnamed watershed immediately south of the MSC that hosts the PML and whose alluvial fan (shaded green in Figure 1) abuts proximal sections of the main lobe’s intact southerly leveeThe “south” watershed, located adjacent to the PML-hosting watershed and north of much larger Dedeckera Canyon. The alluvial fan associated with this small canyon (shaded blue in Figure 1) abuts and is actively eroding the central reach of the intact lateral leveeThe large Dedeckera Canyon watershed (shaded pink in Figure 1), whose associated alluvial fan abuts the toe and distal portions of the MLLandslide debris composing the PML continues to choke the small watershed in which it came to rest. Presumably, similar bodies of landslide debris once occupied portions of the MSC that have since been flushed from the canyon by more vigorous fluvial activity in that larger and more elevated canyon, contributing to formation of the sequence of alluvial fans found at and below the mouth of the canyon (Figure 1).Each of the five watersheds discussed above has experienced at least 2 to 5 m of late Quaternary incision at the mountain front, reflecting the effects of long-term tectonic and/or climatic processes. This incision has exposed the range-bounding normal fault and associated distinctive travertine deposits along the range front north of the ML (Figure 1, Feature 7). We interpret the much greater 25 m incision of the MSC to result from the additional short-term disturbance caused by emplacement of the EVL.The alluvial fans associated with each of these canyons have also experienced at least 1 to 2 m of incision, resulting in the isolation of large, elevated, inactive, or minimally active fan surfaces (Figure 1, stippled pattern). The active, incised portion of the Dedeckera Canyon fan intercepts the toe of the ML. It also contains distinctive rhyolitic volcanic debris, apparently a result of a recent incidence of stream piracy in the upper canyon that is actively eroding a large exposure of volcanic bedrock. Outcrops of volcanic rock are absent or much less prevalent in the other contiguous watersheds. As a result, alluvium associated with the active portion of the Dedeckera Canyon fan is distinguishable by its high concentration of these volcanic cobbles.Following emplacement of the EVL, stream erosion flushed significant volumes of landslide debris from both the MSC and the canyon containing the PML, isolating a small body of lacustrine deposits at the head of the PML (Figure 1, Feature 3) and contributing to the construction of proximal alluvial fans at the mouths of both canyons. The fans constructed at the mouth of the MSC mantled most of the ML upstream from the DH (Figure 1).Exposures near the mouth of the MSC indicate that the fans constructed there ranged up to a maximum of about 6 m in thickness. We estimate that these fans originally covered an area of roughly 45 ha and once extended as far as 950 m from the mountain front. The fan constructed at the mouth of the much smaller PML-containing watershed appears to have covered an area of about 9 ha, extended up to 550 to 600 m from the mountain front, and impinged upon the ML’s southerly lateral levee over a distance of about 250 m (Figure 1).Based on the geomorphology of the PML, we estimate that erosion has removed approximately 6×105 m3 of debris from its host canyon since emplacement. If this erosion occurred within a short time and transferred the entire volume to the proximal fan, it would have produced a postevent alluvial deposit with an average thickness of about 6 to 7 m. More likely, the rate of debris production started off high but tapered off over time. Based on the geomorphology of the fan and comparing with the thickness of the deposits at the mouth of the MSC, we consider it more likely that the PML’s proximal fan never exceeded a thickness of about 5 to 6 m at the mouth of the canyon, tapering to smaller values towards the edges.Following deposition of the proximal fans, the MSC and PML fan heads experienced approximately 25 m and 2 to 5 m of incision, respectively. We ascribe this incision to recovery from the short-term effects of the landslide, coupled with adjustment to unrelated climatic and/or tectonic factors that have affected all the canyons and alluvial fans along this portion of the mountain front. During this period of incision, erosion almost completely removed the ML’s northern lateral levee along with portions of the DH. Similarly, stream flows from the PML canyon eroded much of its proximal fan, breached the southern lateral levee at the mountain front, incised the southerly margin of the MSC’s abandoned proximal fan, and scoured alluvial material from the northerly side of the levee (Figure 1).As discussed previously, the interior base of the levee currently lies about 10 m below its south-facing exterior at most locations (Figure 1). Potential explanations for this elevation difference include (1) scour of the alluvial surface by the ML during emplacement, (2) preferential postemplacement erosion of alluvium from the inner margin of the levee, and/or (3) preferential deposition of alluvium along the outside of the levee.A scour origin for the elevation differential is conceptually straightforward and requires no substantial postemplacement elevation changes to the adjacent alluvial landforms. It also explains the 100 m widening and apparent volume increase of the DH upon exiting the MSC. Hence, the geomorphology of the ML and DH are consistent and compatible with a scour origin for the present configuration of the lateral levee and is our preferred interpretation.The presence of alluvium of unknown depth bracketing the intact lateral levee complicates this simple geomorphic interpretation. Regarding the possibility that the lower interior level of the levee results from postemplacement fluvial scour, we note that landslide breccia is exposed to within 1 to 2 m of the base of the interior slope of the levee, thus indicating that the inner side of the levee extends to a depth of at least 8 to 9 m below the exterior alluvial surface. Hence, the elevation differential between the opposing sides of the levee is not attributable to preferential erosion of alluvium on its inner side.Regarding the alternative possibility, i.e., that the elevation differential between the opposite sides of the levee reflects aggradation along the southerly side of the embankment, we cite the following observations: (1)Proximal levee Profiles E and F (Figure 1) abut bedrock outcrops and are definitively unaffected by external aggradation, yet they exhibit geometries quite like Profiles A-C lower on the fan(2)The alluvial fan associated with the PML watershed abuts the levee section that exhibits the greatest inside-to-outside elevation differential, yet this watershed is much smaller and lower in elevation than the MSC. This indicates, a priori, that sediment production from the PML watershed must be significantly less than from the MSC, a fact inconsistent with much greater depths of alluviation on the PML-fed side of the levee(3)Just below the mountain front, the PML watershed constructed a proximal fan that appears to have banked up against a 250 m long section of the levee following emplacement of the landslide (Figure 1). Flows from the PML watershed subsequently reworked much of this fan and, along with activity along the range-front fault, opened a 50 m wide gap in the levee and triggered ~1 to 2 m of incision on both sides of the levee. Based on the sum of our observations, we conclude that as much as 5 m of aggradation occurred outside the levee in the vicinity of Profile D (Figure 1) following emplacement of the slide and as much as to 4 m of this material remains in place today (Figure 1, Profile D). This aggregation is localized to the area near the mountain front and fails to explain the 10 m inner/outer elevation contrast observed along most parts of the levee(4)At the distal end of the levee, the preserved headscarp stratigraphy exposed at Location X (Figure 1) implies that the base of the landslide currently lies around a meter below the base of the field exposure (Table 6), a finding inconsistent with significant postemplacement aggradation or erosion of the fan surface in this area. These relations imply that the Dedeckera Canyon alluvial fan, which abuts this part of the ML (Figure 1), lies at approximately the same grade today as it did at the time of emplacement of the EVLProximal levee Profiles E and F (Figure 1) abut bedrock outcrops and are definitively unaffected by external aggradation, yet they exhibit geometries quite like Profiles A-C lower on the fanThe alluvial fan associated with the PML watershed abuts the levee section that exhibits the greatest inside-to-outside elevation differential, yet this watershed is much smaller and lower in elevation than the MSC. This indicates, a priori, that sediment production from the PML watershed must be significantly less than from the MSC, a fact inconsistent with much greater depths of alluviation on the PML-fed side of the leveeJust below the mountain front, the PML watershed constructed a proximal fan that appears to have banked up against a 250 m long section of the levee following emplacement of the landslide (Figure 1). Flows from the PML watershed subsequently reworked much of this fan and, along with activity along the range-front fault, opened a 50 m wide gap in the levee and triggered ~1 to 2 m of incision on both sides of the levee. Based on the sum of our observations, we conclude that as much as 5 m of aggradation occurred outside the levee in the vicinity of Profile D (Figure 1) following emplacement of the slide and as much as to 4 m of this material remains in place today (Figure 1, Profile D). This aggregation is localized to the area near the mountain front and fails to explain the 10 m inner/outer elevation contrast observed along most parts of the leveeAt the distal end of the levee, the preserved headscarp stratigraphy exposed at Location X (Figure 1) implies that the base of the landslide currently lies around a meter below the base of the field exposure (Table 6), a finding inconsistent with significant postemplacement aggradation or erosion of the fan surface in this area. These relations imply that the Dedeckera Canyon alluvial fan, which abuts this part of the ML (Figure 1), lies at approximately the same grade today as it did at the time of emplacement of the EVLBased on these observations and the appearance of the levees in the field, we are of the opinion that a 10 m aggradation event affecting the entire southern side of the ML is highly unlikely, that the exposed exterior base of the levee more likely lies within 0 to 4 m of its original deposited position, and that the lower relative elevation of its north side principally reflects the effects of scour by the ML during emplacement of the landslide.Well-developed desert pavements, pitted carbonate clasts, and dark brown varnish on noncarbonate clasts characterize the alluvial surfaces overlying the EVL, providing a minimum age estimate of ~60-80 ka for the deposit [25]. Rough constraints on its maximum age are provided by the character of lacustrine deposits formed near the head of the PML (Figure 1, Feature 3), which formed in response to temporary blockage of local drainage courses by landslide debris. The absence of strong carbonate cementation in these deposits limits their age to roughly 100 ka [36].Figure 3 compares the estimated age range of the EVL with local and global paleoclimatic records over the past 200 ka. Pluvial conditions prevailed in nearby Death Valley at various points during this period, particularly between 10 and 35 ka (marine oxygen isotope stage 2), circa 102 ka (MIS 5c), and between 120 and 186 ka (MIS 5e/6), when the valley supported perennial lakes (collectively “Lake Manly”). These pluvial periods likely correspond with the occurrence of other large-scale late Pleistocene lakes in the Great Basin, including Bonneville, Lahontan, Deep Springs, Fish Lake, Owens, and Searles [35]. In notable contrast, no geologic evidence exists to suggest that the Eureka Valley supported perennial lakes at any point during the Quaternary period [37]. Somewhat dryer but still wetter-than-present conditions prevailed from 35 to 60 ka (MIS 3-4) and between 85 and 102 ka (MIS 5b/c) when Death Valley supported one or more ephemeral saline lakes [38, 39].Based on a minimum age of ~60-80 ka, the presence of the playa deposits impounded by the EVL with a maximum age of ~100 ka and the pluvial history of Death Valley, we tentatively assign the lacustrine deposits at the head of the PML to MIS 5b/c at 85-102 ka and the slide itself to an earlier date, perhaps extending as far back as the Eemian interglacial (MIS5e). It appears doubtful that the EVL could predate the Eemian, as sedimentary deposits formed during the penultimate pluvial period (MIS 6) should exhibit notable carbonate sedimentation not observed in sediments associated with the EVL.For the purposes of the following discussion, we initially address the kinematics of landslide runout, followed by an evaluation of its detailed dynamics. Kinematics describes motion “from the standpoint of measurement and precise description,” whereas dynamics is concerned with “the causes or laws of motion” [40]. In other words, kinematics describes what happened, and dynamics describes why it happened. Too frequently, these issues have been comingled in the technical literature of long-runout landslides since Heim [16]. As such, we make every effort to segregate these issues here.(1) Effective Coefficient of Sliding Friction. Heim [16] introduced the concept of the fahrbӧschung as a semiquantitative measure of the relative efficiency of long-runout landslide transport and emplacement. He defined this measure as the angle of a line connecting the crown of the headscarp with the toe of a long-runout landslide and promoted its use as a surrogate for the angle of the line connecting the initial and final positions of the landslide center of mass, in practice a difficult value to determine. As described previously, Hsü [2] in turn promoted the use of the tangent of the fahrbӧschung, the ratio of the fall height (⁠H⁠) to runout length (⁠L⁠) as a method to compare the relative mobility of long-runout deposits.Among the more enigmatic characteristics of long-runout landslides as a group is their trend towards decreasing H/L ratios with increasing volume following a log-normal relationship, first noted by Scheller [41]. Shaller [9] extended this analysis by breaking out various groupings of long-runout landslides by their degree of confinement, lithology, and other factors. In general, the ML and PML fall within the trend of the larger population of long-runout landslides in H/L vs. Log(Volume) space and close to the regression line for unconfined landslides, indicating that they exhibit similar mobility to these landslides despite being channeled for the majority of their runout. They also exhibit modestly greater mobility than the family of carbonate landslides and somewhat lesser mobility than the terrestrial population of terrestrial Blackhawk-like landslides (not applicable to the PML, which does not share this morphology).Equation (2) represents a “best guess” velocity estimate because it (1) assumes perfect conversion of kinetic energy to gravitational potential energy (thus underestimating true velocity), while (2) failing to account for potential momentum transfer between leading and trailing portions of a moving landslide (thus possibly exaggerating the velocity estimate).The first overtopping point is located where the PML entered its side canyon, accompanied by an elevation rise of approximately 35 m. The second point is where PML debris overtopped a second, 20 m high watershed boundary. The third overtopping point is located along the northern edge of the ML runout track where landslide debris spilled over the divide with the neighboring watershed to the north. This divide stands approximately 90 m above the floor of the MSC.Applying Equation (2), the calculated velocity of the debris at the first, second, and third overtopping points is ≥26 m/s, 20 m/s, and 42 m/s, respectively (Figure 1). These velocity estimates lie towards the lower end of the 20 to 100 m/s range reported for 57 terrestrial subaerial long-runout landslides by Shaller [9].(3) Spreading of Landslide Mass. We estimate that the slide block that contributed mass to the final EVL deposit originally measured approximately 300 m wide by 386 m long by 35 m thick (applying the conclusion that the ML scoured its base during emplacement). Once displaced from the mountainside, the fragmented slidemass encountered a bedrock ridge that split the debris into two principal components. Material that passed to the north of the ridge and ultimately exited the canyon comprised about 60% of the original mass; the remainder moved south to form the PML. Accordingly, approximately the northerly 180 m of the detached slide block contributed to the ML and the southerly 120 m to the PML. By the time the ML debris reached the mouth of the MSC, it measured about 300 m wide and 15 m thick. Relative to the dimensions of the initial source block, this represents a widening of about 175% and a thinning of about 60%. If we assume that the detached slide block experienced 25% bulking during its transit of the MSC, the slidemass would have extended to a length of 675 m by the time it exited the canyon. Notably, this value is approximately equivalent to the final length of the DH.(4) Preservation of Attenuated Headscarp Stratigraphy. The preservation of headscarp stratigraphy in attenuated form is obvious along the southern margin of the ML. It also occurs in one of the northerly side lobes (Figure 1, Location 8) and may exist in the PML. Despite fragmentation of the originally intact limestone block during its descent from the mountainside, these preserved stratigraphic relations indicate that the landslide experienced remarkably little vertical mixing and therefore a very low vertical velocity gradient during runout. We therefore infer that most of the relative movement between the landslide debris and the substrate occurred at or near the base of the landslide (i.e., the landslide slid and did not flow into place).The ~40 : 1 attenuation of source area stratigraphy preserved in exposures along the southerly margin of the ML (Table 6) places additional constraints on the kinematics of emplacement. The teardrop-shaped DH experienced about 1.5x longitudinal and 2.2x lateral extension by the end of movement, implying that the bulk of the deposit should exhibit an approximate attenuation factor of 1.5×2.2≈3:1⁠, less than one-tenth the amount exposed along its southern margin.We propose that the extreme attenuation observed along the eroded southerly edge of the deposit is a boundary effect resulting from shear between the rapidly moving interior and the outer edge of the ML, manifested in the manner of an imbricate thrust sheet laid on edge (Figure 4). Shaller [20] described an analogous texture from the Carlson landslide, Idaho, where large, distinctive, isolated blocks of volcanic agglomerate derived from a unique source area in the headscarp exhibit a “string of pearls” arrangement along one lateral levee due to focused longitudinal extension along the margin of the deposit. Lava flows are known to develop similar marginal shear zones and lateral levees [43]. These observations support the hypothesis that longitudinally attenuated marginal shear zones such as that documented along the margin of the ML may be a common characteristic of moving bodies of soil and rock.(5) Incorporation of Alluvial Substrate. As described above, our preferred geomorphic interpretation is that the ML scoured and incorporated up to 1.6 million m3 of alluvium during its descent of the alluvial fan below the mouth of the MSC, a volume that corresponds to approximately 34% of the total volume of the ML and 37% of the volume of the DH. Entrainment of alluvial substrate material is known or suspected to have accompanied the emplacement of long-runout landslides elsewhere, with the scoured material representing from ~15% [44] to ~820% [27] of the original bulked volume of landslide debris. Based on field observations and experimental debris flow bed scour analyses by de Haas and van Woerkom [45], potential reservoirs of displaced alluvium in the main lobe include (1) accumulation in a bulldozed distal wedge; (2) bulk interleaving of alluvium with carbonate landslide debris; (3) underplating; and (4) fine intermixing with the carbonate breccia. We estimate the maximum volume of a potential bulldozed wedge to be about 105 m3, suggesting that the other listed reservoirs represent more likely repositories of the scoured material, consistent with the comingled appearance of landslide debris and alluvium along the eroded northern edge of the ML.(6) Kinematic Wave Behavior. The longitudinal profile of the DH resembles a breaking wave, with a steep leading edge that tapers in the upslope direction. This profile resembles wave-like impulses elsewhere, including natural phenomena such as debris flows [46]. In general, this geometry arises when more rapidly moving trailing material overtakes the leading edge of a sliding or flowing material. The presence of at least one steeply dipping reverse fault in the DH supports the premise that the leading edge slowed relative to trailing material near the conclusion of runout, resulting in compression between these portions of the slide mass. Possible explanations for the appearance of this feature in the DH include (1) resistance to advancement as a result of bulldozing of a passive wedge of alluvium before the DH (Figure 1, Transect G) and/or (2) progressive downslope reduction in the slope of the alluvial surface, which would affect a slowdown in the leading edge of the slide before the trailing material encountered the same lower slopes.Based on the preceding observations and analysis, we hypothesize three fundamental processes to explain the key characteristics of the EVL. The first and principal of these processes is particle fracture (cataclasis) with energy recycling, which we envision controlling the dynamics of the landslide during its transit of the bedrock canyon areas. The other processes, applicable to the ML as it transited the alluvial fan at the mouth of the MSC, include incorporation of substrate material and localized liquefaction of the alluvial substrate.(1) Proposed Particle Fracture (Cataclasis) with Energy Recycling Mechanism. Rather than representing a mere by-product of emplacement, we interpret slidemass brecciation to be a key process underlying the long-runout phenomenon in the EVL, particularly during its transit of the bedrock canyon areas. We view clast breakage as partially interrupting the process of frictional energy dissipation within and along the base of the moving landslide during runout. In this regard, the proposed mechanism is broadly analogous to previously hypothesized mechanisms that invoke acoustic or mechanical grain flow mechanisms to limit frictional energy losses and extend the reach of large-scale landslides via high frequency intergrain and grain-to-substrate impacts [2, 47–49]. From a geological standpoint, the principal drawback to these grain flow mechanisms is their failure to explain the textures of these deposits [17], specifically (1) grain flow models require that clasts remain intact through the collisional process, whereas field evidence suggests that clast fragmentation is pervasive inside rapidly moving landslides, even to the finest scales [9, 50]; and (2) these mechanisms should produce deposits rich in rounded particle shapes, normal grading, and other textural features common to known geologic grain flow processes such as turbidity currents [51] and pyroclastic sediment gravity flows [52] but largely absent in the EVL and other long-runout landslides.The cataclasis model proposed herein is, in contrast to these other models, consistent with and indeed motivated by the observed texture of the EVL and other long-runout landslides. In this model, the kinetic energy applied to the basal clasts in contact with each other and with the substrate commonly results in their rupture (rather than rebound), thus recycling the elastic strain energy momentarily stored in these clasts back to the landslide in the form of spherical shock waves. Such shock waves would rapidly propagate through the slide mass at a velocity of ~100-1200 m/s [53, 54], substantially faster than its maximum runout speed, thus communicating the effects of clast breakage quickly throughout the body of a rapidly moving landslide.For this proposed mechanism to function, impact rupture must occur throughout the course of runout (or major portions thereof), not just during rare or singular occurrences such as the impact of the slidemass at the base of its initial plunge, as proposed by Shreve [10] for the Blackhawk landslide. While some slidemass brecciation (or disarticulation along existing discontinuities) likely accompanied the EVL’s initial plunge from the headscarp, the character of small-scale landslides and rockfalls tells us that in the absence of some other process, this initial phase of movement would result in a mixed and ungraded mass of rubble at the foot of the source slope. The preservation of headscarp stratigraphy and reverse grading in the EVL instead implies the action of another, far less chaotic, process that operated along the base of the landslide from the outset of the event. We envision focused basal fragmentation of the moving slidemass to be this mechanism.In this treatment, we view the proposed cataclasis mechanism as acting through a modification of the resisting term in Equation (3), which represents the energy dissipation of a landslide block sliding on its bed if taken on a per meter basis (i.e., as work). For purposes of quantification, we approach this problem by resolving the impulse energy from hypothesized breakage-induced shocks into three perpendicular axes relative to the travel direction: vertical, lateral, and longitudinal (Figure 5(b)). Similar to the effects that result from grain collisions in mechanical grain flow simulations [2, 47–49], we envision that the vertical component of the impulses acts to reduce the effective normal force of the landslide on its bed, thereby reducing the effective frictional coefficient of the landslide. The lateral component, in turn, acts to potentially spread the debris normal to the movement direction. The longitudinal component acts to both accelerate the leading edge and slow the trailing edge of the landslide relative to the center of mass, resulting in an increase in the runout length of the leading edge and extending the debris sheet in the longitudinal direction.In addition to frictional losses, ε is expected to depend on factors such as the thickness, velocity, rock strength, and dilation of the rock mass due to fragmentation. While not treated here, we expect the efficiency of clast breakage to increase with velocity and basal loading and decrease with increasing rock strength. Landslides on bodies with lower gravitation should therefore be less efficient than those on Earth because of reduced velocity and basal loading, consistent with the observed behavior of Martian landslides [55].For the end-member case of ε=0⁠, the equations simplify to a basic block-on-inclined-plane analysis. For any value of ε>0⁠, an additional factor is necessary to account for the volume change associated with brecciation of the slide mass (25% volume increase divided by the six cardinal directions). The theoretical maximum value of ε is therefore slightly greater than 1.Following the reasoning in Figure 5(b), we expect the pressure waves produced by the rupturing rock debris to dilate the basal portion of the moving debris, much as acoustic and collisional processes induce dilation near the base of nonfragmenting grain flows [2, 47–49]. Indeed, given the multiplicity of grain interactions occurring near the base of a rapidly moving landslide, nonfragmental grain collisions and their associated phenomena likely contribute in some subsidiary way to the mechanics of these mass movements, a conclusion perhaps supported by the presence of subrounded clasts in the EVL.In addition to explaining the texture and the detailed kinematics of the EVL, the basal fragmentation mechanism also helps explain the observed lack of spattering of rock beyond the limits of the landslide. This is because the cataclasis mechanism and its associated rapid grain motions are expected to primarily occur along the base of the thick, central portion of the moving landslide and not beneath its thinner and slower moving margins.(3) Supporting Observations. For the cataclasis model to function, impact rupture must occur for the duration of runout (or major portions thereof), not just during rare or singular occurrences such as the impact of the slidemass at the base of its initial plunge. Beyond the EVL’s textural characteristics, support for the cataclasis model is available from the mineral processing and aggregate testing fields as well as from the deposits of other long-runout landslides. Specifically: (1)The potential energy released by the falling slidemass was more than sufficient to pervasively fragment the source block during runout(2)Slidemass fragmentation along preexisting discontinuities and via impact-induced tensile and shear failures is reasonable under the conditions prevailing at the base of the rapidly moving landslide(3)Limestone toughness estimates (the energy absorbed by a rock during fracture propagation) are consistent with impact fragmentation during runout(4)Hysteresis effects lower the resistance of limestone clasts to impact fragmentation, thus extending the reach of the mechanism to flatter slopes and lower speeds(5)Microtextural observations from other long-runout landslide provide additional support for the cataclasis mechanismThe potential energy released by the falling slidemass was more than sufficient to pervasively fragment the source block during runoutSlidemass fragmentation along preexisting discontinuities and via impact-induced tensile and shear failures is reasonable under the conditions prevailing at the base of the rapidly moving landslideLimestone toughness estimates (the energy absorbed by a rock during fracture propagation) are consistent with impact fragmentation during runoutHysteresis effects lower the resistance of limestone clasts to impact fragmentation, thus extending the reach of the mechanism to flatter slopes and lower speedsMicrotextural observations from other long-runout landslide provide additional support for the cataclasis mechanism(5) Strength Considerations. In addition to energy considerations, it is also necessary to demonstrate that the EVL’s constituent rock fragments could reasonably experience impact fragmentation in the environment of a moving landslide. Clast strength is controlled by the strength of bedrock discontinuities, intact rock strength, and mineral hardness.Because impact fragmentation is a dynamic process, dynamic rock strength represents the most important parameter for determining whether this process may reasonably occur in a moving landslide.Published strength data for limestone, summarized in Table 9 [58–65], indicates that: (1)Limestone is strongest in compression, with strength values one to two orders of magnitude higher than in shear or tension. The dynamic compressive strength is even greater, increasing linearly with impact load [60, 65](2)The static and dynamic shear strength of limestone are of similar magnitude, with the dynamic strength exceeding static values by no more than 25% [61](3)The dynamic and static tensile strength of limestone are roughly equivalent [62](4)As expected, the shear strength of limestone discontinuities is very low, roughly one to two orders of magnitude below that of intact rock [58]Limestone is strongest in compression, with strength values one to two orders of magnitude higher than in shear or tension. The dynamic compressive strength is even greater, increasing linearly with impact load [60, 65]The static and dynamic shear strength of limestone are of similar magnitude, with the dynamic strength exceeding static values by no more than 25% [61]The dynamic and static tensile strength of limestone are roughly equivalent [62]As expected, the shear strength of limestone discontinuities is very low, roughly one to two orders of magnitude below that of intact rock [58]Clast fragmentation requires the imposition of impact forces that exceed the minimum strength of the constituent clasts. Hence, based on the preceding strength ranking, we surmise that fragmentation would initially involve disarticulation of the rock mass along preexisting discontinuities, followed by breakage of intact clasts via shear or tensile failure. In the context of a rapidly moving landslide, failure in shear is expected to result from tangential/glancing blows, whereas tensile failure is hypothesized to occur by means of clast impacts sufficiently energetic to “split” the rock normal to the impact load. The latter failure mode is analogous to that in the standard Brazilian tensile strength test [66].Dynamic failure of limestone by shear or tensile fracture would entail the application of an impact pressure of at least 4 MPa to a target clast, which is readily achievable inside a rapidly moving landslide. To illustrate, we consider the following hypothetical: a 1 kg clast impacts another rock fragment at a relative velocity of 40 m/s with a contact time of 0.1 s, yielding an impact force of 400 N. Application of this force to an area of 1 cm2 results in a force per unit area of 400 N/0.0001 m2 or 4 MPa. If the clasts rebound from one another or from the substrate after impact, the applied force/area would be double this value. More than likely, clast fragmentation is driven by localized concentrations of pressure on individual clasts caught at the basal contact between a large mass of moving debris and the stationary substrate (especially bedrock).(6) Toughness Considerations. Rock strengths, such as the tensile and shear strength, are one measure of its resistance to brittle failure. Another measure of rock resistance to brittle failure is the energy absorbed by the rock during fracture propagation, referred to as material toughness. The Los Angeles Abrasion (LAA) test is the standard test method for evaluating rock toughness. For coarse aggregate (>19 mm), the test involves revolving 10 kg of dry material together with twelve steel balls collectively weighing 5 kg in a 70 cm diameter drum for 1000 revolutions at 30 to 33 rpm [67]. A fin in the drum lifts the rock and steel balls, allowing them to tumble down onto the material below, creating an impact-crushing effect. After the prescribed number of revolutions, the contents are removed, the aggregate portion is sieved to remove all material finer than 1.7 mm, and the remainder weighed. The final weight divided by 10 kg gives the sample attrition.The peak velocity achieved by the 0.42 kg steel balls typically used in the LAA apparatus is approximately 3.3 m/s or less, associated with a freefall distance of about 55 cm and an impact energy of about 20 J. The published LAA test results for limestone and dolomite indicate that after 1000 cycles, these materials experience significant impact attrition, with attrition rates that range from 24 to 36% [67, 68]. Given the much higher velocity of the EVL (often over 40 m/s) and the long distance of travel (over a kilometer across rugged, exposed bedrock), the accumulation of thousands of impacts with energies in excess of 20 J appears likely in the constituent debris. Hence, the results of the LAA test imply a high likelihood of impact fragmentation of limestone and dolomite rock types in the moving landslide during runout from a toughness perspective.(7) Hysteresis Effects. Prolonged cyclic loads reduce rock strength due to the accumulation of microfractures in the affected material. For all rock types, test methods, and failure types, Cerfontaine and Collin [69] report a steady reduction in rock strength with the number of accumulated load cycles, with strengths diminishing by about 15% after 103 load cycles and 22% after 106 cycles. For the special case of limestone, Haimson [63] reported 50 to 75% reductions in tensile strength and 25 to 30% reductions in compressive strength following application of 103 to 105 load cycles. Kamonphet et al. [70] report no notable reductions in limestone shear strength over a course of 10 shear cycles, while Okada and Naya [64] report a 15 to 20% reduction in the shear strength of tuff and artificial sandstone following application of 103 load cycles (Table 9).Although the number of load cycles experienced by the clasts in a rapidly moving landslide is difficult to judge, movement over a rugged landscape should induce many load cycles in the affected clasts, perhaps as many as one per meter of travel or more. At a speed of 40-50 m/s, this would imply 40 to 50 cycles per second and the accumulation of between 104 and 105 load cycles per kilometer of travel. Seismic recordings of rapidly moving landslides have documented frequencies in the 40-50 Hz range [71], supporting the hypothesis that load cycles accumulate rapidly in such events.(8) Microtextural Considerations. In extremely energetic landslide environments, clast breakage is followed by the breakdown of the individual mineral grains [9, 50]. In common rock durability tests such as the Los Angeles (ASTM C 535, LAA) and mill abrasion tests, this process is controlled by mineral hardness [67]. It is unknown whether this process took place in the EVL. The process is, however, known from other examples, including the Martinez Mountain [9] and Travertine [50] landslides of southern California. In both examples, petrographic analysis of fine, coherent samples of rock breccia from the base of these landslides captured “freeze frame” images of individual mineral grains in the act of fragmenting and dispersing in a fine-grained matrix. The imagery from these petrographic analyses provides a visual guide to the functioning of the comminution process at work in these landslides and helped inform the comminution mechanism envisioned herein.(9) Application of the Cataclasis Model to the Eureka Valley Landslide. To test the proposed cataclasis model for the EVL, we applied Equations (8), (10), and (13) to simplified runout path geometries for the ML and PML derived from Google Earth topography (Table 10). As shown in Table 10, the modeled runout path geometry for the ML consists of seven segments of known length and slope angle, while eight segments were utilized to model the PML in recognition of its more sinuous travel path. Source blocks for the ML and PML were each subdivided into nine subblocks (numbered from lowest to highest on the source slope), whose center of gravity accelerations, velocities, and travel distances was followed in a spreadsheet calculation as they transited their runout paths. Initial block dimensions parallel to slope were taken as 31 m for the PML and 75 m for the ML calculations. Figure 4 shows the modeled travel path geometries, the locations of major break points, and the calculated starting and ending positions of the centroids of each of the subblocks.Application of the cataclasis model entails calculation of variable accelerations for each of the in-tandem slide blocks, the magnitude of which depends on the gravitational acceleration, slope angle, and location relative to the other sliding blocks. Except in the immediate vicinity of slope transitions, Block 1 always experiences the greatest acceleration (Equation (10)) and the trailing block the lowest (Equation (13)), with intervening blocks experiencing intermediate values depending on the number of blocks in motion at any given time (Table 11). The start of a nine-block simulation utilizes the accelerations shown in the first row of Table 11. During a runout simulation, the trailing block, having the lowest acceleration, stops first. When the original trailing block (Block 9) comes to a halt, the accelerations of the remaining eight blocks shift to the second row in the table, and so on, until only Block 1 remains in motion. At this point in the simulation, the cataclasis mechanism is “shut off,” and Block 1 is permitted to slide to a halt using an unmodified frictional coefficient, μ, equal to 0.5.(10) Application to the Minor Lobe. Table 12 shows the results of application of the cataclasis model to the PML. The model results shown in the table apply for an efficiency factor, ε=0.88⁠, which provides a best match for the full suite of observed and inferred characteristics of the deposit. As noted in Table 10, the top of the minor lobe “Upper Scarp” corresponds to the upper contact of the Carrara Formation with the overlying Bonanza King Formation. This location was chosen because the Carrara Formation comprises nearly the entirety of the deposit. Though very little of the distinctively gray Bonanza King Formation limestone is present in the PML, a short additional “sacrificial” slope section is included in the calculations to account for the mass of slide material that must at one time have occupied the canyon area upslope from the minor lobe that has since been removed by erosion.As shown in the second column of Table 12, the peak velocities of the nine PML starting blocks, calculated at the base of the “Initial Plunge” just below the headscarp, range from 26 to 48 m/s. These velocity estimates meet or exceed the 26 m/s minimum velocity necessary for the landslide debris to climb the 35 m high opposing slope at the base of the initial plunge and enter the adjacent watershed. In the absence of the cataclasis mechanism or some other means of lowering the effective friction of the sliding rock, none of this slide material would have overtopped the wind gap and entered the adjacent watershed. For reference, Figure 4 shows the calculated velocity of the leading edge of the minor lobe at various points along its runout path.In addition to the velocity estimates, both the overall length and the final mass distribution of the PML calculated using the cataclasis model are generally consistent with field evidence. Specifically, the cataclasis model predicts a distally tapered geometry, consistent with observations. The final profile geometry is obtained from the model by assuming that the initially 31 m long sliding blocks experience longitudinal spreading during runout to maintain contact with neighboring blocks; the farther the endpoints of neighboring blocks are to one another, the thinner the deposit.(11) Application to the Main Lobe. The favorable results achieved by application of the cataclasis model to the PML suggest the model is reasonably applicable to the translation of a long-runout landslide through a bedrock canyon. Application of the cataclasis model to the runout of the ML resulted in the following findings: (1)Conveyance of the white limestone marker bed from the mountainside to the mouth of the canyon and beyond by means of the cataclasis model requires a high efficiency factor—close to 1—as compared with the 0.88 value applied to the PML. Justification for the higher efficiency factor includes (a) the greater average thickness of the ML debris and (b) the lesser degree of bulk deformation accumulated by the ML during runout. The latter interpretation is based on the contrast between the well-preserved headscarp stratigraphy exposed in portions of the ML versus the major folding and deformation exposed in the interior of the minor lobe(2)A trailing mass of material that did not itself exit the canyon is necessary to push material containing the white marker bed past the mouth of the canyon. The calculations suggest that the trailing edge of this missing slope section came to rest nearly 300 m upstream from the mouth of the canyon, as shown in Table 13 and Figure 4. This trailing mass represents a volume sufficient to fill the lower end of the canyon to an average depth of about 15-20 m(3)The velocity calculated for the leading edge of the ML at the mouth of the MSC (43 m/s) correlates well with the velocity calculated to have been necessary for the ML debris to overtop the watershed boundary to form the nearby northern minor lobe (42 m/s at Location 9 on Figure 1)(4)The inferred kinematics of the transit of ML debris through the MSC are consistent with energy recycling via impact fragmentation and hysteresis of the constituent clasts(5)The cataclasis model significantly underpredicts the final runout phase of the ML on the alluvial fan below the mouth of the canyon (Figure 4)Conveyance of the white limestone marker bed from the mountainside to the mouth of the canyon and beyond by means of the cataclasis model requires a high efficiency factor—close to 1—as compared with the 0.88 value applied to the PML. Justification for the higher efficiency factor includes (a) the greater average thickness of the ML debris and (b) the lesser degree of bulk deformation accumulated by the ML during runout. The latter interpretation is based on the contrast between the well-preserved headscarp stratigraphy exposed in portions of the ML versus the major folding and deformation exposed in the interior of the minor lobeA trailing mass of material that did not itself exit the canyon is necessary to push material containing the white marker bed past the mouth of the canyon. The calculations suggest that the trailing edge of this missing slope section came to rest nearly 300 m upstream from the mouth of the canyon, as shown in Table 13 and Figure 4. This trailing mass represents a volume sufficient to fill the lower end of the canyon to an average depth of about 15-20 mThe velocity calculated for the leading edge of the ML at the mouth of the MSC (43 m/s) correlates well with the velocity calculated to have been necessary for the ML debris to overtop the watershed boundary to form the nearby northern minor lobe (42 m/s at Location 9 on Figure 1)The inferred kinematics of the transit of ML debris through the MSC are consistent with energy recycling via impact fragmentation and hysteresis of the constituent clastsThe cataclasis model significantly underpredicts the final runout phase of the ML on the alluvial fan below the mouth of the canyon (Figure 4)In view of these results, we consider the cataclasis mechanism capable of explaining the travel of the ML debris through the MSC. The exceptional mobility of the ML in traversing the alluvial fan, however, requires an alternative explanation based on the available field evidence, as outlined below.(12) Hybrid Mechanism. When the ML exited the source canyon, it traveled approximately three times farther than predicted by the cataclasis model (and much farther still than a typical frictional coefficient would allow) while evidently bulldozing and incorporating 1.6 million m3 of alluvium in its path. In the process, it developed a distally raised profile, distinguishing it from the tapered distal end of the PML. Based on these observations, we consider it unlikely that the cataclasis mechanism controlled the final runout phase of the ML. Instead, we hypothesize that the sudden imposition of load by the fast-moving landslide debris induced liquefaction of the alluvial substrate near the mouth of the MSC, triggering a process that controlled the subsequent movement of the landslide.Several workers have posited substrate liquefaction during the emplacement of large, rapid landslides in more temperate environments, including Europe, Canada, Japan, and the U.S. Pacific Northwest [27, 72]. Several long-runout landslide deposits in arid and semiarid regions also contain evidence of the type of substrate liquefaction proposed herein in the form of syn- and postdepositional clastic dikes. Examples from California and Nevada include the Blackhawk, El Capitan, Tin Can Flat, Travertine, and Vallecito landslides [9, 73].Three field observations support a liquefaction hypothesis for the final movement stages of the ML: (1) the presence of mudflow-like textures exposed along its eroded margin near the mouth of the MSC, (2) the presence of a clastic dike in the northwesterly minor lobe, and (3) the presence of an anomalous sedimentary deposit located immediately northwest of the DH, mapped as unit Qo? on Figure 1.We attribute the cited evidence of substrate liquefaction to rapid loading and the imposition of major shear stresses on a locally saturated fringe of the alluvial substrate by the rapidly moving landslide debris as it emerged from the MSC. Based on the estimated depth of scour that occurred below the mountain front, the liquefaction event evidently initiated within the upper 10 m of the original surface just below the mouth of the canyon. We conjecture that this depth coincided with the location of a perched paleo-groundwater table fed by episodic stream flows from the MSC and seepage and springs along the range-bounding frontal fault (expected to act as an aquitard), likely supported by cooler and/or wetter conditions at the time of the landslide circa 100 to 120 ka (Figure 3). We expect that this near surface water lay in a relatively narrow band along the range front, as is commonly the case along range-bounding faults in the Basin and Range province. Given the 27 ha area of the DH and an average thickness of 0.3 m for the liquefied layer, we estimate the process required the entrainment of roughly 80,000 m3 of saturated alluvium. Given the 300 m width of the debris mass as it exited the main canyon and an excavation depth of 10 m, this would correspond to a width of about 27 m for the wetted zone along the range front. This width correlates well with Google Earth measurements of riparian zone widths along range front faults in areas such as the Wasatch Front, Utah, and the San Andreas Fault Zone of southern California. We envision that, once entrained, the rapid downhill movement of the ML spread the wetted material along the bottom of the debris pile, with agitation keeping it in a liquefied condition for the short duration of runout. Johnson [73] invoked a similar mechanism to explain the exceptional long runout of the Blackhawk landslide of southern California, stating, “…the Blackhawk landslide may have traversed the alluvial apron as a two-layer composite debris flow in which a thick, probably low-fluidity, marble breccia layer rode upon a relatively thin, high-fluidity, sandy mud layer.”Clastic dikes are relatively common in the Blackhawk landslide and several of the other examples listed above. The relative absence of clastic dikes in exposures of the ML may relate to the fact that this landslide occurred in a dryer climate and was smaller, thinner, and lighter than these cited occurrences, thus limiting the amount of liquefied material produced and the overpressures available to inject the fluid into the overlying breccia. Alternatively, liquefied alluvial materials exposed in the bulldozed distal wedge at the cessation of movement may have experienced lateral venting rather than intruding into the overlying breccia to form clastic dikes.The apparent clastic dike at Location 8 (Figure 1) provides supporting evidence for the presence of shallow groundwater conditions near the mouth of the canyon at the time of the landslide. The material forming the dike appears to consist of fault-related travertine deposits. Based on this evidence, we conjecture that the landslide corresponded in time to a period of active seepage/spring activity at the range-bounding frontal fault and that the landslide incorporated saturated travertine material as it overran the nearby frontal fault.Potential additional evidence for substrate liquefaction during ML emplacement also occurs far from the mountain front. Wrucke and Corbett [13] mapped the Qo? unit (Figure 1) as a dune deposit. Our geomorphic interpretation is that this feature may instead represent an outflow of liquefied alluvium that emerged from the toe of the DH upon the cessation of movement. The Qo? deposit has a surface area of about 22 ha and a volume of about 350,000 m3; as such, it would represent about a fifth of the volume of the alluvium we interpret to have scoured by the ML as it descended the alluvial fan. Although a paucity of good field exposures and a mantle of recent alluvium and drift sand complicate its interpretation, the unit is clearly composed largely of alluvial material and not drift sand. Taken together with the flow-like form of the deposit, these sedimentary characteristics provide tentative support for the outflow interpretation.A potential alternative interpretation of the feature is that it represents a relict alluvial surface dating to the emplacement of the landslide and preserved by the sheltering action of the DH, which tends to deflect upslope runoff toward the floor of the valley. In this interpretation, the flow-like appearance of the deposit in aerial images results from the fortuitous arrangement of erosional channels around the margins of the deposit. Causes of erosion in this area include the lingering effects of landslide-related disturbances to the source watersheds, tectonic, and climatic factors.Although the debris that would ultimately form the main lobe was moving in excess of 40 m/s when it arrived at the mouth of the MSC, its velocity was still insufficient to convey the debris 1.7 km down the alluvial fan in the absence of some exceptional friction-reducing material or process. The cataclasis model, for example, only predicts another ~500 m of runout below the mountain front (Table 13, Figure 4).Table 13 provides a detailed summary of the effects of the implied liquefaction event on the runout of the ML as it exited the MSC. This analysis began with the calculated velocities of Blocks 1 through 6 as they exited the mouth of the source canyon (based on application of the cataclasis model, the material represented by Blocks 7 through 9 came to rest in the canyon upstream from the mountain front). Other inputs to the calculation include the slope of the alluvial fan surface and the estimated final locations of the blocks (Table 13; Figure 4, Insert A), which were used as a proxy for the mass distribution, with equal areas assigned to each block. This analysis resulted in the calculation of effective frictional coefficients of 0.13 to 0.16 for the blocks traversing the alluvial fan (Table 13), equivalent to sliding friction angles of approximately 7 to 9 degrees, greatest for the leading edge and lowest for the trailing edge. The higher frictional coefficient of the leading-edge material is attributed to resistance caused by bulldozing of alluvial sediments ahead of the ML during its traverse of the alluvial fan.Although the calculated coefficients of sliding friction calculated here are rather low, they are nonetheless substantially greater than the inclination of slopes known to experience liquefaction-induced lateral spreads in major seismic events, which can be as low as 1 degree [74]. Residual friction angles of 7 to 9 degrees suggest a residual strength for the liquefied material of about 50 to 60 kPa, consistent with literature values for the upper bound of known incidents of soil liquefaction [75].In summary, we infer that once the ML debouched onto the alluvial fan at the mouth of the MSC, it liquefied the substrate and traversed the fan as essentially a rapid, high strength lateral spread. The overall runout mechanism of the EVL consisted of a hybrid between the cataclasis model in the bedrock canyon areas and liquefaction/lateral spreading on the alluvial fan.Other emplacement mechanisms have been proposed or can be envisioned to explain the long runout and other characteristics of the EVL, of other Blackhawk-like landslides, and of other long-runout landslides in general [2, 8, 10, 16, 17, 20, 27, 29, 47, 49, 55, 72, 73]. We briefly examine the most relevant of these alternate hypotheses here as they relate to the EVL, including (1) sliding on a clay-rich substrate [8], (2) subaqueous emplacement [8], (3) air layer lubrication [10], (4) plastic flow [55], and (5) sliding on a frozen substrate. Proposed mechanical and acoustic grain flow models [2, 47, 49, 54] have already been treated in this discussion and will not be touched upon further here.Watkins [8] proposed a mechanism for emplacement of the EVL main lobe that invoked basal lubrication by hydrated clay materials. This hypothesis was based on (1) the possible identification of hydrated materials at the base of the landslide in ASTER remote sensing data and (2) the preservation of headscarp stratigraphy and other geologic structures exposed in the deposit.Watkins [8] utilized remote sensing data collected by the ASTER satellite to evaluate for the presence of clay minerals in the vicinity of the EVL. Table 14 shows the spectral ranges and spatial resolution of the 14 ASTER bands [76]. Watkins [8] cited an ASTER 4 : 8 band ratio image to identify potential hydrated materials (i.e., clays) in the EVL, interpreting a light-colored arc at the toe of the ML in the image to reflect exposures of hydrated clays along the exposed base of the deposit. As reported by Gomez and Lagacherie [77], common clay minerals induce an absorption band around 2200 nm (ASTER band 6), whereas calcium carbonate causes an absorption band around 2340 nm (ASTER band 8; Table 14). Because band 8 reflectance is low for carbonate-rich material, ASTER band 4 : 8 ratio images are not well targeted to the identification of clay minerals but would appear bright for areas rich in carbonates. This conclusion is consistent with the appearance of the ASTER band ratio 4 : 8 image collected in the vicinity of the EVL. Here, slopes underlain by the carbonate-rich upper Wood Canyon, Carrara, and Bonanza King Formations all appear light in tone, whereas slope areas underlain by the Zabriskie Quartzite appear dark, reflecting the relative carbonate content of these formations [31]. Based on these observations, we conclude that the light-colored areas of the ASTER 4 : 8 image cited by Watkins [8] as indicative of areas underlain by hydrated clay minerals, including the light-colored arc at the toe of the ML, in fact highlight areas rich in exposed carbonate materials. We interpret the darker shade of the balance of the ML to reflect its burial by a thin veneer of silica-rich aeolian silt.While we agree with Watkins [8] that the preservation of headscarp stratigraphy and the structure of the EVL’s ML are consistent with a basal lubrication mechanism, we disagree that clay played any significant role in its runout. Beyond the lack of support for clays in the remote sensing data, our field reconnaissance of the landslide uncovered no visual evidence for clay deposits in the area, and our XRD data (Table 7) demonstrate an almost complete lack of clays in the landslide debris itself. Furthermore, clays do not form reliable lubricants except when saturated and sheared slowly [78]. Based on these observations and considerations, we conclude that clay lubrication is not a viable mechanism for emplacement of the EVL.Watkins [8] also proposed subaqueous emplacement as a potential alternative (or adjunct) to basal lubrication by hydrated clay materials for the EVL, citing both its long-runout behavior and the morphology of the ML, which “resembles that of some subaqueous landslides.” This hypothesis is problematic for a variety of reasons. Subaqueous conditions are, for one, clearly not a necessary precondition for long runout of large, rapid landslides. Moreover, various terrestrial and extraterrestrial landslides share the Blackhawk-like morphology of the EVL, which is also not diagnostic of subaqueous emplacement (Figure 2). Subaqueous emplacement of the EVL is, additionally, problematic because of a lack of evidence for a standing body of water in Eureka Valley during the entirety of the Quaternary period.Neither lakebed deposits nor geomorphic evidence such as shoreline features exists to support the hypothesis that a standing lake existed in Eureka Valley during Quaternary time [37]. Nearby Owens Valley and Death Valley, by comparison, preserve shoreline features estimated to date from MIS 6 to 12 [80, 81], well older than the estimated maximum age of the EVL. The lack of persistent water bodies in Eureka Valley during the Quaternary period is attributable to its location in the rain shadow of 3000 m to 4000 m high peaks in the Inyo and Sierra Nevada Mountains and to elevated sill heights that preclude inflow from adjacent well-watered watersheds. The most recent persistent lake(s) in the valley date to the mid-Pliocene, approximately 3.5 Ma, likely reflecting paleo-Owens River flow into the valley at that time [37]. Based on the weight of these observations, we consider subaqueous emplacement an unsustainable hypothesis for the EVL.The air layer lubrication hypothesis championed by Shreve [10] to explain the long runout and other peculiarities of the Blackhawk landslide of southern California and its morphological analogs remains a popular hypothesis that often appears in introductory geology texts [82–85]. Objections to the air layer hypothesis for Blackhawk-like landslides include the presence of morphologically similar deposits on nearly airless Mars and truly airless Ceres (Figure 2) as well as a spectrum of other textural and physical issues [17, 73]. Beyond these observations, we include the following specific constraints for the EVL: (1)The absence of a mechanism that would allow the landslide debris to reach the mouth of the canyon with sufficient velocity to be launched onto the alluvial fan. The angle of repose of crushed rock is typically in the range of 35 to 45°, whereas the angle between the source area and the mouth of the MSC is 21°. Hence, barring the action of some mobility-enhancing mechanism from the outset of motion, the landslide debris should not have exited the source canyon at all. Johnson [73] recognized this issue as problematic for the Blackhawk landslide itself.(2)The lack of an obvious launch ramp. The ML traveled down the MSC and debouched onto the alluvial fan at its mouth without encountering an obvious topographic step that would allow it to become airborne to capture and compress a layer of air beneath; and(3)Scour of the alluvial substrate accompanying emplacement of the main lobe precludes a “gentle hovercraft-like” descent of the fan by the rapidly moving debris. The air layer lubrication model envisions the imposition of a compressed air cushion between the alluvial surface and the landslide debris during its traverse of the fan, a concept inconsistent with scour of the alluvial surface by the rapidly moving breccia.The absence of a mechanism that would allow the landslide debris to reach the mouth of the canyon with sufficient velocity to be launched onto the alluvial fan. The angle of repose of crushed rock is typically in the range of 35 to 45°, whereas the angle between the source area and the mouth of the MSC is 21°. Hence, barring the action of some mobility-enhancing mechanism from the outset of motion, the landslide debris should not have exited the source canyon at all. Johnson [73] recognized this issue as problematic for the Blackhawk landslide itself.The lack of an obvious launch ramp. The ML traveled down the MSC and debouched onto the alluvial fan at its mouth without encountering an obvious topographic step that would allow it to become airborne to capture and compress a layer of air beneath; andScour of the alluvial substrate accompanying emplacement of the main lobe precludes a “gentle hovercraft-like” descent of the fan by the rapidly moving debris. The air layer lubrication model envisions the imposition of a compressed air cushion between the alluvial surface and the landslide debris during its traverse of the fan, a concept inconsistent with scour of the alluvial surface by the rapidly moving breccia.Based on the weight of these observations, we consider air layer lubrication to also represent an unsustainable hypothesis for the EVL.Plastic behavior is a characteristic of many common household substances, such as paint, ketchup, and toothpaste. It has also been proposed to explain the flow of certain materials of geologic origin, including lava flows and debris flows. The fluid-like forms and sheet-like geometries expressed by many long-runout landslides have led to suggestions they too exhibit bulk plastic flow behavior [55]. Such materials experience flow when subjected to basal shear stresses beyond a certain material-dependent “yield stress” [30]. In the case of landslides that exhibit an elevated water content, such behavior is both reasonable and demonstrable [20, 44]. In the case of long-runout landslides composed of dry rock, however, the presence of abrupt internal discontinuities and the preservation of headscarp stratigraphy argue against classical concepts of flow and in favor of basal sliding with localized internal deformation.The significance of Equation (20) is that the larger the slope angle, σ⁠, the smaller the flow thickness, D⁠. To test whether Equation (20) holds for the EVL, we made nine measurements of deposit thickness, D⁠, and ground slope in the movement direction, σ⁠, along the margin of the deposit (Figure 4) using a combination of field measurements and Google Earth topographic profiles along 50 m-long transects parallel to the slide margin. A plot of these data exhibits considerable scatter but generally yields a positive correlation between deposit thickness and surface slope (Figure 4, Insert B, dashed line). This trend is the opposite of that anticipated if the landslides were acting as a plastic flow (dotted line in Figure 4, Insert B, calculated assuming a yield strength of 8,500 Pa). Hence, a plastic flow hypothesis is rejected for the EVL because it fails to explain both the details of its interior structure as well as its detailed geometric form.As shown in Figure 3, the EVL likely occurred during a cooler and possibly wetter-than-present period. As such, we assessed the available evidence for emplacement by sliding on a frozen substrate. Despite the frigid connotations associated with glacial episodes in much of North America, Eureka Valley lies far to the south of the recognized southern limit of permanently frozen ground in North America during the last glacial maximum (MIS 2) [87]. Moreover, peak temperatures in Death Valley generally stood about 10°C higher during the time assigned to the landslide than during the last glacial maximum (Figure 3), further reducing the likelihood of emplacement on an ice-covered surface or buried permafrost layer. The inferred 10 m deep excavation of the alluvial substrate during emplacement of the ML also precludes sliding on a temporary surficial sheet of ice or mantle of snow following a rare freeze or snowstorm. Hence, we consider sliding on a frozen substrate an improbable mechanism for emplacement of the ML.Between approximately 60 and 120 ka, a block of Cambrian-age limestone with a volume exceeding 5 million m3 detached along a planar discontinuity at its source in the Last Chance Range and rapidly accelerated downhill. The moving mass of breccia separated into two unequal lobes at the base of its initial plunge. The smaller lobe, comprising roughly 40% of the failed mass, traveled to the south and came to rest in a side canyon. The larger lobe passed to the north of the ridge and traveled the full length of the main source canyon, with most of its mass ultimately debouching onto the alluvial fan at its mouth. Upon reaching the mouth of the MSC, the main lobe excavated a ~10 m deep trench down the length of the alluvial fan and incorporated about 1.6 million m3 of displaced material into its mass, thickening and widening its distal heap.Pervasive brecciation of the slidemass accompanied detachment of the slidemass from the mountainside and its transit through the bedrock canyon areas. Rather than being a simple by-product of the landslide process, we interpret slidemass brecciation to instead reflect a key process underlying the movement of large, rapid landslides that traverse rocky slopes and canyons. The physical process envisioned here involves recycling of the elastic energy of the breaking clasts into the moving debris, greatly enhancing landslide mobility. This process, in principle, should function in any terrestrial or extraterrestrial setting in which the constituent rock mass can experience brittle, impact-driven tensile, or shear failure during emplacement.As the ML exited the MSC, it encountered a much weaker, locally wet, alluvial substrate that succumbed to liquefaction in response to rapid loading and shearing, prompting a second phase of movement. Taking over from the cataclasis-driven mechanism as the debris exited the MSC, basal liquefaction extended the reach of the rapidly moving debris by roughly a kilometer beyond that possible by way of the cataclasis mechanism alone.No field evidence exists to support alternative mechanisms such as sliding on a basal layer of saturated clay, frozen ground, or air. The field evidence also excludes subaqueous emplacement of the ML, emplacement as a plastic flow, or mobilization of the landslide by any mechanism requiring the constituent clasts to maintain their integrity (such as acoustic or mechanical grain flow).These findings present a means to better predict the reach of future long-runout landslides that often accompany large-scale slope failures. Among the key insights provided by this research is the recognition that the dimensions of the failed source block, the geometry of the runout track, and the nature of the substrate all play significant roles in governing the runout experienced by large, rapid slope failures, and thus, all represent important elements in assessing the risks afforded by future large-scale mass movements. In the face of the extremely violent and energetic forces applied by a large, rapid landslide on its base, the behavior of the weakest material prevails. When traveling over a rock surface, it is the strength of the constituent clasts that govern the process, but when the debris encounters a weak substrate, such as a saturated soil, the properties of the soil govern.The consequential geologic, geometric, and environmental factors addressed herein should, in most instances, be accessible and quantifiable by qualified field personnel. In areas of extreme sensitivity, such as rugged watersheds hosting (or lying upstream from) large population centers, such investigations seem warranted. A key to exploiting this opportunity is the successful hindcast of other well-constrained long-runout landslides in the historical and geologic record.The authors declare that there is no conflict of interest regarding the publication of this article.ESi (Engineering Systems Inc.) and Exponent, Inc. provided financial support for field work and laboratory testing. The authors wish to thank Keith Shaller, Steve Okubo, Greg Ferrand, and Jeff Knott for valuable field assistance and Jeff Knott, Jeffrey Keaton, Ann Shaller, Keith Shaller, Pravi Shrestha, and Kristina Cydzik for helpful editorial reviews and discussions.

中文翻译：

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尤里卡河谷滑坡：长跳动滑坡双重破坏机制的证据

在世界许多山区，长期滑坡是众所周知的臭名昭著的地质灾害。这些快速的大规模移动通常包括大量碎片，它们通过直接影响和间接危害（如下游洪水）使人口处于危险之中。尽管它们具有明显的风险，但这些大规模滑坡的机理仍然令人费解且有争议。在这项工作中，我们阐明了位于加利福尼亚中东部死亡谷国家公园的尤里卡谷（Eureka Valley），一个更新世晚期，保存良好且长期保存的长突变滑坡的内部构造。滑坡起源于最后机会山脉北部崎north的西北露头，使寒武纪基岩脱离了500万立方米以上。它的规模相对紧凑，形态保存完好，多样的岩性成分，以及通过侵蚀过程进行的战略解剖，使其成为研究干燥环境中长期失控现象的出色实验室。尤里卡山谷的滑坡与地球，火星和小行星谷神星上的微型，形态相似的“类似黑鹰”滑坡相似，包括南加州著名但规模更大的黑鹰滑坡。像其他滑坡一样，尤里卡河谷的滑坡由一个叶状的，远端抬高的主波瓣组成，并由抬高的侧向堤坝界定。像其他地面实例一样，它主要由遍布裂缝的，由裂口支撑的角砾岩组成。基于滑坡的地质特征及其推断的运动学，提出了一种由两部分组成的位移机制：（1）在基岩峡谷地区活跃的劈裂-断裂机制（分解），以及（2）在滑出主要峡谷时滑坡的主要波瓣遇到并液化的饱和沉积物基底上滑动。先前推测的解释滑坡的高速跳动和形态及其类似黑鹰的类似物的机制显然与该矿床的地质，地貌和矿物学及其沉积环境不一致。长跳动的滑坡是该地区显着的地质灾害世界上许多山区，包括北美和南美，欧洲和亚洲的大部分地区。风险包括高移动性碎片对人口中心和基础设施的直接影响[1-3]，泥石进入立式水体[4]，以及滑坡坝的形成和破坏[5]，从而导致下游洪水泛滥。除了滑坡水坝所代表的物理危害外，它们还可能在偏远地区积蓄大量水，影响下游地区的水质和可利用性[6]。我们预计，这些危害只会随着时间的推移而增加，以应对山区和下游山区的人口压力和基础设施的增长。尽管存在这些明显的危害，仅在20世纪，这些生命就花费了成千上万人的生命，跳动的滑坡仍然是神秘的和有争议的。本工作旨在阐明一种暴露异常严重且受限制的长期滑坡滑坡的内部工作原理，以将其应用于全球范围内的此类较大特征，其共同目标是更好地控制这些主要滑坡所代表的危害并逐步发展。更好地了解环境因素在促进其长期活动中的作用。尤里卡山谷滑坡位于尤里卡沙丘东南方，位于尤里卡山谷南端，加利福尼亚中东部，死亡谷国家公园，纬度37 °04′27″ N，经度117°38′49″ W（图1）。滑坡起源于晚更新世晚期最后机会区中央的寒武纪石灰岩西北向凹凸不平的露头和沉积岩层。继McKeown和Bishop [7]最初对它进行描述之后，我们对该特征采用了非正式名称Eureka Valley滑坡（以下简称EVL）。沃特金斯[8]根据光学刺激发光方法提供了最低年龄估计为8.3-9.4 ka，并提出了黏土润滑和/或水下安置机制来解释其长距离传输。EVL以相对紧凑的形式展示了许多长期滑坡的典型特征，特别是“黑鹰式”滑坡。Shaller [9]将类似Blackhawk的滑坡定义为形态简单，干燥的岩石长径迹滑坡的一个子组，类似于南加州著名的Blackhawk滑坡[10]。其他地面实例包括南加州的银礁滑坡[10]，加利福尼亚州欧文斯山谷附近的纽约比尤特滑坡[11]，以及阿根廷西部[12]记录的一系列类似矿床。类似黑鹰的滑坡也发生在火星[9]和矮行星谷神星上（图2）。在这里，我们用术语“长径滑坡”代替“ sturzstrom”，“岩石雪崩”和“ rockslide雪崩， ”，这是此类快速，大规模群众运动经常使用的其他术语，以避免使用它们所暗示的机械关联。此外，从盆地分析中避免使用较旧的术语“巨型角砾岩”，尽管这些著名的沉积物经常代表着古代长径滑坡沉积物的遗迹。Hsü[2]将长径滑坡定义为具有下降高度（距顶冠垂直距离）的滑坡。到脚趾，H）到行进长度（冠和脚趾之间的水平距离，L）比率小于0.6。Hsü[2]将该比率命名为Heim [16]之后的“fahrböschung”，该词从德语原义翻译为“旅行坡度”。Heim [16]也将此措施称为“能量线”。出于各种原因，更好地理解EVL非常重要。原则上，该矿床为难以捉摸的运输机制提供了宝贵的见解，而这些运输机制导致了快速暴动和大规模滑坡的长期跳动和其他特征，这是一个多世纪以来的争论[17]。更好地了解这一基本地质过程对于改善山区地形的滑坡灾害风险评估至关重要。这项研究的另一个有价值的产品是对这些沉积物的沉积学有了更好的了解，在美国西部的盆地和山脉地区，它作为石油储层发挥着重要作用[18，19]。这项研究还提供了有关该地区地质学的新见解，包括在最近的一次冰川/沼泽事件中地表水的可利用性和地下水的深度。最后，对EVL及其形态类似物的更好理解已经达到了利用滑坡形态远程监测过去和现在其他行星体（特别是火星）表面上的液态水可用性的目标[9，20]。三个主要成分中的一个（图1）：位于山前下方冲积山​​麓上的一个突出的主瓣（以下称ML），位于其东南部的山脊和峡谷上的一对“次要瓣”（不规则形状的石灰石角砾岩堆积物）。 ML 另一对较小的裂片位于ML跳动轨道的西北部。ML本身由两个主要部分组成：水滴形的“远端堆”（以下称为DH）和界定其跳动轨道南部边缘的升高的侧堤。根据与其他地区形态相似的滑坡的比较（图2），假定类似的堤坝最初位于该矿床的北部，此后一直遭受侵蚀.EVL出现在1：62,500比例的Last Chance Quadrangle地质地图上Wrucke和Corbett [13]。该矿床位于东北走向的最后机会山脉的西北边缘，露出寒武纪粉砂岩，砂岩，石英岩和碳酸盐岩沉积层的层序（图1）。从最老到最年轻，包括早期的寒武纪木峡谷构造，早，中寒武统Zabriskie石英岩，中寒武纪卡拉拉组，中至晚寒武纪Bonanza国王组。除沿边界断裂的前部断层变形外，这些沉积物局部表现出中度的东南（坡内）倾角。范围前部以第四纪晚期正断层为界[21]，其中包括一对东北向的断裂带，它们抵消了滑坡和邻近的冲积层。两条正常断层陡坡的剖面与形成陡坡的地震的Mw 7.1至7.3事件一致[22]。1993年5月17日在山谷西侧附近发生的6.1级大松木地震是尤里卡山谷记录的最大历史地震事件。这次地震与滑坡西北6至21 km的山谷中心部分发生了一系列小地表破裂有关，但在滑坡附近没有其他陡坡[14，23]。 ，尤里卡谷地受到更远地震源[23]的震动，包括死亡谷（东北13公里）和欧文斯谷断层带（西南53公里）。后者与1872年加利福尼亚州最大的历史地震龙隆地震有关，据估计在尤里卡谷地产生了大约VIII级地震动[24]。EVL主要来自卡拉拉和博南扎国王地层的基岩。卡拉拉地层局部由黄棕色，棕色和灰棕色夹层石灰岩，粉质石灰岩，粉砂岩，砂岩和页岩。Bonanza国王组由黑色白云质石灰岩和偶有白色石灰岩带组成。EVL起源于未命名的“主要水源峡谷”（以下简称MSC）上游的西北陡坡，面积341公顷，流域面积约1,040 m的垂直浮雕和约2130 m的峰高。未命名的相邻的南风域包含主要次要叶（以下称PML）。它是一个36公顷的流域，具有约415 m的垂直浮雕和约1,550 m的峰高。其他附近的流域通过与其相关的冲积扇影响EVL，如图1所示。表1总结了这些流域的关键特征。Schlom和Knott [14]绘制了EVL和附近的冲积扇表面（图1）。今天，覆盖在滑坡近端的冲积层高出排水MSC的有效通道25 m。冲积层的裸露厚度最高达6 m，并且局部展现出发达的沙漠路面，点状碳酸盐碎屑和非碳酸盐碎屑上的深棕色清漆。这些特征类似于附近死亡谷的冲积面，年代为60-80 ka [25]。近端冲积扇沉积之后的25 m扇头切口在一定程度上代表了扰动前的分水岭特征。然而，附近的其他地貌证据表明，在MSC口处观察到的切口包括与滑坡无关的构造和/或气候相关过程的影响[26]。这些证据包括在射程前沿附近部分有约2至5 m的扇头腐蚀和约1-2 m的冲积扇切口。ML的向南边缘也遭受了积极的侵蚀，沙丘覆盖的冲积沉积物的西北边缘也受到侵蚀（图1，Qo？单元）。这种广泛的侵蚀活动的潜在潜在原因包括范围限定的正常断层活动的下降和/或与从更新世向全新世气候条件的转变相关的碎片产生的减少。 EVL包括（有关特征的位置，请参见图1）：特征1：位于滑坡源区上方和北部的山脊裂缝（袋状）特征2：卡拉拉石灰岩角砾岩的一个小裂片，在大约1,295 m的高程上超过了水源流域的北缘，与侵蚀修整线的西偏界相对应。特征10：卡拉拉石灰岩角砾岩的一系列局部返修露头，代表了一个河道的侵蚀残余曾经有大量角砾岩沉积在MSCFeature 11口附近：在峡谷底上方约50-100 m处有一条侵蚀性的“修剪线”，显然是由滑坡碎屑的冲刷形成的；修剪线在沿MSC北侧约700 m的Google Earth影像中可见。这些要素已在可行的情况下进行了实地验证，但要素1、2和11除外，这些要素仅由Google Earth影像和/或远程野外观察来解释。表2–5总结了EVL的关键物理特性。除非另有说明，否则所有标高，距离和面积的测量都取决于Google Earth的地形。EVL的许多形态和质地特征类似于其他长期开采的滑坡沉积物上暴露的特征。表2列出了这些特征以及它们在其他地方的相对患病率。[9]如上所述，EVL由突出的主瓣和一系列次瓣组成。当超速质量块在MSC的上游遇到一条横穿其路径的基岩山脊时，就开始将滑层分成不同的裂片。大约60％的碎片通过了该山脊的右侧（北部），然后下山，形成了ML和向北的次要裂片。剩下的40％传递到左侧（南部），形成PML和一个小的副瓣。各种次要瓣的不规则形状是由于它们最初弯曲的行进路径和进位后侵蚀所致，形成ML的碎屑在其下坡道的前1,500 m处仍保持通道状，从MSC的口出来，宽度约为根据峡谷的几何形状和堤坝在其口处的高度，厚度为300 m，厚度超过约15 m（图1，剖面E和F）。此后，它从冲积扇下降到峡谷口以下时，经历了相当大的扩散和增厚。从运动结束时开始，ML从最初的约300 m的宽度扩展到了约400 m的宽度（即增加了133％），并经历了远端20 m的增厚。尽管出现了 不是类似于泥石流堤的简单建筑地貌。相反，根据五个Google Earth地形图（图1，Transects AF），其内边缘通常比其相应的外边缘低10 m，这已通过使用Ziplevel®电子水位的Transects AC的现场测量得到了证实。这些观察结果表明，ML在安置过程中侵蚀了其床层，并在冲积扇下降时吸收了多达160万立方米的基质材料（相当于在16公顷的区域中冲刷了10 m的冲刷水，该区域以大堤，山腰和远侧为界）堆）。这个隐含的体积巧妙地平衡了ML的扩大和增厚所代表的体积。表5总结了EVL及其主要成分的面积和体积，包括冲积冲刷的影响和将完整岩石转化为角砾岩的体积因子为25％[27]。如图所示，由EV的各个叶代表的完整石灰岩的估计总体积在4.2至5.5百万立方米之间，具体取决于伴随ML进位的基础冲刷程度.ML主要由碎屑支撑，成角的呈圆形倒角的角砾岩，表现出粗略的反向坡度，以大量散落在沉积物表面的大块巨石为代表。颗粒大小差异很大，从粉砂或粘土大小的岩粉到直径几米的巨石不等。在几个地方，滑坡碎片普遍破裂，但很少被折断，这种质地在其他地方被称为三维拼图角砾岩[10]。在更好的规模上 粗条纹通常是水平下取向。突然的晶粒尺寸和其他纹理变化，偶发的凿子状材料的出现以及扭曲的垫层的存在表明这些特征代表了内部剪切带。在DH的北侧（图1中的Y位置），这些剪切特征之一急剧陡峭地倾斜到了56°的角度（向东南倾斜，向上倾斜），呈现出反向断层的外观。在露头尺度上，南部边缘被侵蚀了ML提供了保存完好的头皮地层的壮观例子。在这里，基部暴露的三分之二由棕色至黄棕色的卡拉拉地层角砾岩，上三分之一的灰色，白色和黑色的Bonanza King角砾岩组成。后者包括一个独特的，膨胀的白色记号笔床，以及从矿床表面突出的大部分巨石。这些支离破碎的基岩单元相对于其在斜坡上的完整几何形状被根本性地衰减，但在其他情况下几乎没有混合，但保留了它们的原始地层层序和相对厚度。将位置X处的色带厚度（图1）与斜坡上完整的相关色带进行比较，得出位移材料的衰减比约为40：1（表6）。根据与head鳞碗中暴露的基岩关系的比较，该衰减比表明滑坡的底部可能比暴露底部低一米.ML的北侧受更广泛的侵蚀，暴露出更复杂的阵列纹理和结构。在MSC口附近，角砾岩覆盖了伍德峡谷地层的基岩山脊，然后倾斜地切割了原始冲积层（图1，位置Z）。该地区的露头使灰色至白色石灰岩角砾岩暴露在覆盖石灰岩为主的冲积层上，其中含有少量其他类型的岩石。角砾岩和下面的冲积层在颜色和质地上的相似性使得这些单位在许多野外暴露中相对难以区分，并且许多暴露的物质可能代表两种物质的混合或指间沉积[28]。然而，在当地，滑坡-冲积层的接触很容易识别。在一个这样的位置，该接触点以30厘米厚，由基质支撑的，通常为梯度的，具有砾石间隔的粉质砂子标记。较大的砾石和鹅卵石似乎已经沉降到该层的底部，以及其上表面与覆盖的滑坡角砾岩之间的接口。总体而言，该纹理暗示了滑坡和冲积层之间的流化边界层。与ML不同，PML几乎完全由棕色至黄棕色的Carrara石灰岩角砾岩组成。然而，灰色石灰岩角砾岩的单板覆盖了许多露头，暗示了另一种保留的头皮地层实例，Bonanza King角砾岩覆盖了卡拉拉地层衍生的物质。与ML中一样，水平内部的内部滑动表面很常见，通常并列对比颜色和纹理的角砾岩。在局部，颜色均匀且纹理化的角砾岩带变形为弓形和人字形褶皱，其波长和幅度范围约为2至10 m。在一个侵蚀雕刻的弓形底部的一个位置（图1，特征4），大约10厘米厚的边界层夹在下面完整的基岩和上面对比鲜明的质地和颜色的角砾岩之间。该层主要由分类较差的砂砾和砾石大小的石灰岩角砾岩构成（表7），并且可横向追踪至离开基岩表面并侵入上覆滑动块的位置。对从边界层收集到的物质进行X射线衍射分析的结果证实了滑坡的主要碳酸盐岩性以及其中所含粘土矿物的浓度极低（表7）。附近，基岩中的局部凹陷包含长达30 cm角砾石和鹅卵石，依次由较细的角砾岩覆盖。我们将这些关系解释为代表滑坡的粗粒度前缘的局部沉积，沿着坡度下降时，地形上填充了低点。在加利福尼亚州南部的马丁内斯山岩石雪崩的底部也存在类似的关系，它们以更大的比例存在[9，29]。局部暴露于PML的细粉含量足以形成基质支撑的纹理。小规模的堤坝沿该区域的沉积物边缘出现，类似于那些通常有界的泥石流沉积物[30]。尽管存在这些局部流体似的构造和特征，但滑坡支配的主要支撑构造与典型的泥石流沉积物截然不同。孤立的滑坡角砾岩块超过了MSC口附近的北向排水道并进入放在相邻的北峡谷的斜坡上（图1，位置8和9）。在位置8，一个滑坡角砾岩体，约10 m厚，覆盖着分水岭的山脊。这次暴露主要由卡拉拉组角砾岩构成，顶部是黑色的Bonanza King石灰岩块，代表了滑坡体中保存的地层序列的第三个例子。在滑坡其他地方观察到的卡拉拉和博南扎国王石灰岩块表现出三维拼图拼图纹理，并伴有海绵状风化作用。滑坡的底部在位置8的附近很好暴露沿其与下伏的伍德峡谷地层的接触处数十米。在此位置，当地衍生的伍德峡谷碎屑与主要来自卡拉拉的滑坡角砾岩形成了实质性的混合物，表明基岩表面存在明显的局部冲刷。附近，浅棕色至白色的基质沿接触面渗入滑坡角砾岩，并延伸到矿床体内。这种浅色的矩阵在滑坡暴露中是唯一的，表明在跳动期间可能与额叶断层相关的钙华沉积物局部合并。这种材料似乎已经侵入了下面的基岩的破裂表面，通过止动型机制使岩石的角板松动和脱离。可以在附近的碎屑混合物中观察到类似的物质，并形成碎屑堤防，该碎屑堤防侵入矿床山顶附近大约10垂直米处的一块黑色的Bonanza King石灰石块。角砾形成发生在位置9，它超出了MSC的排水沟，并沿着陡峭的北坡向下倾斜。产生的沉积物是散乱的砾石，鹅卵石和巨石。一系列因素为EVL斜坡破坏奠定了基础。沿尤里卡河谷断层带的第四纪隆升产生了必要的隆升，并导致沿山前部分的陡峭地形，并伴随着卡拉拉和波南萨国王组之间的风化差异。正如死亡谷地区这些单元的常见现象一样，硅质的卡拉拉石灰岩是一种斜坡形成物，而上覆的波南萨国王石灰岩和白云岩是一个形成悬崖的单元[31]。在此基础上，我们假设，卡拉拉组长期的优先风化时期导致在斜坡失稳之前，EVL源区的Bonanza King组逐渐侵蚀性地蚀，相交，谷倾，中度至陡倾节理相交。 Bonanza国王组进一步降低了超陡坡的稳定性。根据Google Earth影像，这些关节组似乎可以控制源区距骨堆积上方大平面坡度区域的几何形状。图1显示了通过应用三点几何方法计算出的这些关节组的估计方向。陡峭的山坡和活跃的构造环境促使在carp头东北部的山脊线向滑坡头突出的地方形成了明显的袋囊特征（图1，特征1）。Sackung特征的形成是由于失去侧向支撑（通常在冰川地区）或由于响应地震地面加速度引起的间歇性运动而引起的山脊线重力扩展而引起的[32]。该观察结果表明，在头皮附近的某些关节表面经历了长期的差异运动历史。基岩地层与ML中暴露的地层的比较表明，保留在最终沉积物中的陡峭岩带的最高部分是一个突出的白色石灰岩标志层，该层露于距骨覆盖的头皮碗的边缘，预计位于附近碗内海拔1,737 m。在海拔约1,545 m处，标志性床与the鳞碗底部之间的斜坡长度约为386 m。假设head果碗大约为300 m宽，我们计算出保存在最终矿床中的滑块部分最初测得的宽度大约为300 m，长度为386 m（平行于坡度），厚度为35至47 m（垂直于坡度） ）。较低的厚度估计值对应于最大ML冲刷冲刷的情况。较厚的厚度适用于无粘性的情况。carp果碗的地貌表明，原始的边坡破坏包含的物质多于现有滑坡沉积物所占的比例。这种缺少的物质由最初存在于白色标记床上方的斜坡区域中的Bonanza King基岩组成，向上倾斜延伸至约1900 m处新出现的平面陡坡的顶部。陡峭和颜色变化的明显中断标志着该陡峭的山顶，位于山脊线下方约50 m；超过此限制，岩体更暗，风化程度更高。斜坡破坏中包含的一些岩石保留在前，钵中以形成其中存在的重要距骨沉积物，但大部分从前the出来并可能沉积在MSC中。表8提供了估计的海拔，尺寸，和在EVL期间从carp果碗中移出的岩石量。它还提供了估计的仍然残留在the果碗中的碎屑作为距骨（约50万立方米）的量。陡坡顶部陡壁流域的滑坡后侵蚀产生了约50万立方米，约占总量的十分之一。剩余的45万立方米由源自原始坡度破坏的材料组成，该材料在破坏后仍保留在head果碗中。这种核算使我们对初始边坡破坏量的估计增加到4.9至660万立方米，但产生了约0.8至120万立方米的“漏失”量，它既不是距骨也不是我们目前对滑坡碎片的核算。我们将在随后的讨论中评估这种额外置换材料的含义和处置方式。滑坡的触发事件未知。EVL与活跃的第四纪断层的接近使滑坡的地震触发有可能是合理的，尽管是有争议的。尤里卡河谷的降雨稀少，2013年至2019年的年平均降雨量仅为62毫米/年。[33]今天大部分的年降水量都发生在冬季，并且可能由于周围较高峰上的积雪而下降。即使在更新世晚期，年平均降水量也可能不会超过现代值的两倍[34，35]。由于在更新世晚期高海拔地区积雪可能很显着，因此霜冻楔形是坡面破坏的潜在附加因素。鉴于源头地区的地形极其陡峭，山脊中直接降雨的积累或地下水位的升高似乎都不是引发滑坡的因素，但是陡峭的地形可能会导致斜坡蠕变（可能集中在先前存在的不连续处），已知这种现象会加速发展成这种规模的大规模边坡破坏[9，16]。EVL的到来影响了沿范围前沿的几个连续流域的径流和泥沙产生（图1，表1），进而修改了滑坡的地貌。这些修改已充分改变了沉积物的形态，从而需要对局部流域及其相关冲积扇的演化进行单独处理。这些相关的分水岭包括：（1）MSC，（2）相邻的未命名“北”流域，其中有两个较小的滑坡碎片残骸裂片（3）。相邻的未命名的分水岭，位于拥有PML和其冲积扇的MSC南部（图1中的绿色阴影） ）紧靠主瓣完整的南堤（4）的“南部”分水岭，毗邻PML承载分水岭，在更大的Dedeckera峡谷以北。与这个小峡谷相关的冲积扇（图1中为蓝色阴影）邻接并正在积极侵蚀完整的侧堤的中央范围（5）。大迪克德拉峡谷分水岭（图1中为粉红色阴影），其相关的冲积扇与ML的脚趾和远端 产生滑坡的相邻未命名“分水岭”，拥有两个较小的滑坡碎片残骸。紧邻位于承载PML的MSC南部的相邻未命名分水岭，其冲积扇（图1中为绿色阴影）紧靠主凸角的近端部分。完整的向南堤防“南部”分水岭，毗邻PML承载分水岭，在更大的Dedeckera峡谷以北。与这个小峡谷相关的冲积扇（图1中的蓝色阴影）邻接并正在积极侵蚀完好的侧堤的中央范围。大型Dedeckera峡谷分水岭（图1中的粉红色阴影），其相关的冲积扇邻接脚趾和远端。构成PML的MLLandslide残骸中的残骸继续窒息了它赖以生存的小流域。想必，相似的滑坡碎片体曾经占据了MSC的一部分，此部分由于更大而更高的峡谷中更剧烈的河流活动而从峡谷中冲走，从而形成了在峡谷口及其下方发现的冲积扇序列。 （图1）在上述五个流域中，每个流域在山前都经历了至少2至5 m的第四纪晚期切口，这反映了长期的构造和/或气候过程的影响。该切口已揭露了沿ML北部向前的范围边界正常断层和相关的独特钙华沉积物（图1，特征7）。我们解释说，MSC的25 m切口要大得多，这是由于EVL的置入引起的额外短期干扰所致。与这些峡谷中的每一个相关的冲积扇也经历了至少1-2 m的切口，从而隔离了大的，升高的，不活跃或最小活跃的扇面（图1，点状图）。Dedeckera Canyon风扇的主动切口部分拦截了ML的脚趾。它还含有独特的流纹岩性火山碎屑，这显然是最近在上峡谷发生的河道盗版事件的结果，该事件正在积极侵蚀大量火山岩层。在其他连续的分水岭中，火山岩露头不存在或少得多。结果，与Dedeckera Canyon风扇活动部分相关的冲积层因其高浓度的这些火山卵而有明显的区别。河流冲刷从MSC和包含PML的峡谷中冲洗掉了大量的滑坡碎屑，从而隔离了PML顶部的一小片湖相沉积物（图1，特征3），并有助于在该处构造近冲积扇。两个峡谷的嘴巴。在MSC口处构造的风扇掩盖了DH上游大部分ML（图1）.MSC口附近的暴露表明，在那里构造的风扇的最大厚度约为6 m。我们估计这些风扇最初占地约45公顷，并且曾经从山前延伸到950 m。在包含PML的小流域口处构造的风扇似乎覆盖了约9公顷的区域，从山前延伸到550至600 m，并在大约250 m的距离上撞击了ML的南侧堤坝（图1）。根据PML的地貌，我们估计，冲撞从侵蚀以来已从其宿主峡谷清除了约6×105 m3的碎片。如果这种侵蚀在短时间内发生并将整个体积转移到近端扇形体上，则将产生事后冲积沉积物，平均厚度约为6至7 m。更有可能的是，碎屑产生的速度开始很高，但随着时间的流逝逐渐减小。基于风扇的地貌，并与MSC口处的沉积物厚度进行比较，我们认为PML的近端风扇在峡谷口处的厚度从未超过约5至6 m的可能性更大，并且逐渐变细沿边缘减小到较小的值。MSC和PML风扇头分别经历了约25 m和2至5 m的切口。我们将此切口归因于从滑坡的短期影响中恢复，以及对不相关的气候和/或构造因素进行了调整，这些因素已经影响了沿山锋这一部分的所有峡谷和冲积扇。在切割的这段时间内，侵蚀几乎完全清除了ML的北侧堤岸以及部分DH。同样，来自PML峡谷的水流侵蚀了其近端扇的大部分，冲破了山前的南部侧堤，切开了MSC废弃近端扇的南缘，并从堤的北侧冲刷了冲积物（图1） ）。如前所述，目前，在大多数位置，堤防的内部基础位于其朝南外部下方约10 m（图1）。这种高低差的可能解释包括：（1）冲积过程中ML对冲积物表面的冲刷；（2）冲积物在堤坝内缘的优先冲蚀后侵蚀；和/或（3）冲积物沿外部的优先沉积高程差异的冲刷起源在概念上很简单，并且不需要对邻近冲积地貌进行大的安置后高程变化。这也解释了离开MSC后DH的100 m加宽和表观体积增加。因此，ML和DH的地貌与当前侧向堤的构造的冲刷起点一致且兼容，是我们的首选解释。未知深度的冲积层包围完整的侧向堤的存在使这种简单的地貌解释变得复杂。关于堤坝内部较低水位是由筑坝后河流冲刷造成的，我们注意到滑坡角砾岩暴露于堤坝内部斜坡基部的1至2 m之内，因此表明堤坝的内侧延伸至外部冲积层以下至少8至9 m的深度。因此，大堤相对两侧之间的高度差并不归因于冲积层内侧的优先侵蚀。关于替代可能性，即 堤坝相对两侧之间的高程差反映了路堤南侧的沉积，我们引用以下观察结果：（1）近堤坝轮廓E和F（图1）紧靠基岩露头，并且绝对不受外部侵蚀的影响，但它们的几何形状很像风扇上的Profiles AC下部（2）。与PML分水岭相关的冲积扇紧靠堤顶部分，该断面展现出最大的内外高程差，但是该分水岭小得多且海拔较低比MSC。先验地表明，PML分水岭的沉积物产量必须显着少于MSC的产量，这一事实与堤坝的PML喂养侧（3）刚好在山前下方的冲积深度更大不一致，PML分水岭构造了一个近端风扇，在滑坡发生后，它似乎已经倾斜到堤防的250 m长部分（图1）。随后，PML分水岭的水流重新改造了大部分风扇，并伴随着沿山前断裂的活动，在堤防中打开了50 m宽的缝隙，并在堤防的两侧引发了约1-2 m的切口。根据我们的观察总和，我们得出结论，在放置滑梯之后，在堤坝D的附近（图1），在堤坝外部发生了多达5 m的积聚，并且多达4 m的这种物质仍保留在原位。今天（图1，配置文件D）。这种聚集作用仅限于靠近山前的区域，无法解释沿堤坝大部分地区观察到的10 m内外高程对比度（4）。在堤坝的远端，保留的头皮地层在X位置暴露（图1）表示滑坡的底部目前位于野外照射的底部下方一米左右（表6），这一发现与该区域风机安装后的严重积聚或侵蚀不符。这些关系表明，与ML的这一部分邻接的Dedeckera Canyon冲积扇（图1）如今与EVLP堤防概貌E和F（图1）邻接时的位置大致相同。基岩露头，绝对不受外部凝结的影响，与PML分水岭相关的冲积扇紧靠在堤坝段上，该坝段具有最大的内外标高差，但该分水岭比MSC小得多，且标高比MSC低。先验地表明，PML分水岭的沉积物产量必须明显少于MSC的产量，这一事实与大堤的PML供给侧的冲积深度更大不一致，只是在山腰以下，PML分水岭构造了一个滑坡发生后，近端风扇似乎已倾斜到堤防的250 m长部分（图1）。随后，PML分水岭的水流对该风扇进行了大修，并且伴随着沿山前断裂的活动，在堤防中打开了一个50 m宽的缝隙，并在堤防的两侧触发了约1-2 m的切口。根据我们的观察总和，我们得出结论，在放置滑梯后，在堤坝D的附近（图1），在堤坝外部发生了多达5 m的积聚，并且多达4 m的这种物质仍然存在今天（图1，配置文件D）。这种聚集作用仅限于靠近山前的区域，无法解释沿堤坝大部分地区观察到的10 m内外高差。在堤坝的远端，保存在位置X处的保存的头皮地层（图1）暗示目前，滑坡的底部位于野外照射的底部下方一米左右（表6），该发现与该区域风扇安装后的严重凝结或风扇表面腐蚀不符。这些关系表明，与ML的这一部分邻接的Dedeckera Canyon冲积扇（图1）今天的位置与EVL定位时的位置大致相同。在田间，我们认为影响ML整个南侧的10 m凝结事件极不可能发生，堤防裸露的外部基底更可能位于其原始沉积位置0到4 m之内，并且北侧较低的相对海拔高度主要反映了ML在滑坡形成期间冲刷的影响。发达的沙漠路面，点状碳酸盐岩屑，非碳酸盐岩屑上的深褐色清漆是覆盖EVL的冲积层的特征，为该矿床提供了约60-80 ka的最小年龄估算[25]。在PML顶部附近形成的湖相沉积物的特征提供了对其最大寿命的粗略限制（图1，特征3），该沉积物是由于滑坡碎屑暂时阻塞局部排水过程而形成的。这些矿床中没有强固的碳酸盐胶结作用，将其年龄限制在大约100 ka [36]。图3将EVL的估计年龄范围与过去200 ka的局部和全球古气候记录进行了比较。在此期间，死亡谷附近的各个地点普遍存在盆景状况，特别是在10至35 ka（海洋氧同位素第2阶段），大约102 ka（MIS 5c）和120至186 ka（MIS 5e / 6）之间，当山谷支持多年生湖泊（统称为“曼利湖”）时。这些冲积期可能与大盆地中其他大型晚更新世湖泊的发生相对应，包括邦纳维尔，拉洪坦，深泉，鱼湖，欧文斯和塞尔斯[35]。与此形成鲜明对比的是，没有地质证据表明尤里卡河谷在第四纪的任何时候都支持多年生湖泊[37]。当死亡谷支持一个或多个短暂盐湖时，干燥的条件仍然有些湿润，但仍比现在湿润（35至60 ka（MIS 3-4），在85至102 ka（MIS 5b / c）之间[38，39]。根据最低年龄约60-80 ka，最大年龄约100 ka的EVL蓄积的普拉亚沉积物和死亡谷的暴雨史，我们尝试将PML顶部的湖相沉积物以85-102 ka的价格分配给MIS 5b / c，并将滑坡本身分配到较早的日期，也许可以追溯到Eemian冰川间期（MIS5e）。EVL可能早于Eemian，这是令人怀疑的，因为倒数第二个雨季（MIS 6）期间形成的沉积物应该表现出与EVL相关的沉积物中未观察到的明显的碳酸盐沉降。滑坡跳动的运动学，然后对其详细动力学进行评估。运动学“从测量和精确描述的角度描述运动”，而动力学则与“运动的原因或规律”有关[40]。换句话说，运动学描述了发生的事情，动力学描述了发生的原因。太频繁了 自从海姆[16]以来，这些问题在长期滑坡的技术文献中已被提及。因此，我们将尽一切努力在这里隔离这些问题。（1）有效的滑动摩擦系数。Heim [16]引入了fahrbӧschung的概念，作为长期滑坡滑坡运输和安置相对效率的半定量度量。他将该度量定义为连接head果树冠和长径滑坡的脚趾的直线的角度，并推广了该方法作为连接滑坡质心初始位置和最终位置的直线的角度的替代方法，实际上很难确定一个值。如前所述，Hsü[2]继而促进了fahrbӧschung切线的使用，跌落高度（⁠H⁠）与跳动长度（⁠L⁠）的比值作为比较长径流沉积物相对流动性的一种方法。在长径流滑坡作为一个整体的更神秘的特征中，它们的趋势是Scheller [41]首先指出，随着对数正态关系的增加，随着体积的增加，H / L比值降低。Shaller [9]通过根据局限程度，岩性和其他因素划分出各种类型的长期滑坡进行了扩展。总的来说，ML和PML属于H / L与Log（Volume）空间中长期失控的滑坡种群的趋势，并且接近无限制滑坡的回归线，表明它们表现出与这些滑坡相似的迁移率尽管他们的大部分选拔都被引导。它们还表现出比碳酸盐滑坡族适度更大的迁移率，而比陆生黑鹰状滑坡的陆地迁移率略低（不适用于不具有这种形态的PML）。公式（2）表示“最佳猜测”估算速度，因为它（1）假设将动能完全转换为重力势能（因此低估了真实速度），而（2）却没有考虑到移动滑坡的前部和尾部之间的潜在动量传递（因此可能夸大了最高估计点位于PML进入其侧面峡谷的位置，并伴随着大约35 m的海拔上升。第二点是PML碎片超过第二个20 m高的分水岭边界的位置。第三个过顶点位于ML径迹轨道的北边缘，滑坡碎屑洒在分隔线上，相邻的分水岭向北。该距离位于MSC地板上方约90 m处。根据公式（2），计算出的第一，第二和第三超越点的碎屑速度为≥26m / s，20 m / s和42 m / s（图1）。这些速度估算值接近于Shaller [9]报告的57处地面地下高跳动滑坡的20至100 m / s范围的下限。（3）滑坡质量的扩散。我们估计对质量有贡献的滑块最终的EVL沉积物原先的尺寸约为300 m宽x 386 m长x 35 m厚（适用于ML在安置过程中冲刷其底部的结论）。一旦从山坡上移开，破碎的滑积体就会遇到基岩山脊，将碎屑分成两个主要部分。到达山脊北部并最终离开峡谷的材料约占原始质量的60％；其余的则向南移动以形成PML。因此，分离的滑块的向北大约180 m对ML起作用，向南向120 m对PML起作用。到ML碎片到达MSC的口时，它的大小约为300 m，厚度为15 m。相对于初始源块的尺寸，这表示约175％的变宽和约60％的变薄。如果我们假设分离的滑块在其通过MSC的过程中发生了25％的体积膨胀，那么到离开峡谷时，滑块的长度将达到675 m。值得注意的是，该值大约等于DH的最终长度。（4）保护性Head头地层的保存。沿ML的南缘，头皮地层的衰减形式很明显。它也发生在北侧瓣之一（图1，位置8）中，并且可能存在于PML中。尽管原始完好的石灰岩块在从山坡下降时会破碎，但这些保留的地层关系表明，滑坡的垂直混合非常少，因此在跳动期间垂直速度梯度非常低。因此，我们推断出滑坡碎片与基底之间的大部分相对运动都发生在滑坡的底部或附近（即滑坡滑移而没有流入原位）。〜40：沿ML的南缘（图6）暴露的震源中保留的震源区地层衰减1（表6）给布置的运动学带来了额外的限制。水滴形的DH在运动结束时经历了大约1.5倍的纵向和2.2倍的横向延伸，这意味着沉积物的大部分应表现出大约1.5×2.2≈3：1⁠的衰减系数，不到其衰减系数的十分之一。我们认为，沿沉积物向南侵蚀的边缘观察到的极端衰减是边界作用，它是由ML的快速移动的内部和外部边缘之间的剪切所引起的，表现为波纹状推力纸放在边缘上（图4）。Shaller [20]描述了爱达荷州卡尔森滑坡的类似质地，该处大型，独特，由于沿沉积物边缘的集中纵向延伸，从头皮中唯一的源区中分离出的火山结块块表现出沿一个侧堤的“珍珠串”排列。已知熔岩流会形成相似的边缘剪切带和侧向堤坝[43]。这些观察结果支持这样的假设，即沿ML边缘记录的纵向衰减的边缘剪切带可能是土壤和岩石运动体的共同特征。（5）冲积基质的结合。如上所述，我们首选的地貌解释是，在MSC口下方的冲积扇下降时，ML冲刷并掺入了高达160万立方米的冲积层，体积大约相当于ML总体积的34％和DH总体积的37％。冲积基质材料的夹带是已知的或被怀疑伴随着其他地方长期滑坡滑坡的发生，冲刷的材料占原始体积的滑坡碎片的约15％[44]至〜820％[27]。根据野外观察和德哈斯和范·沃科姆[45]进行的实验性泥石流床冲刷分析，在主瓣中置换冲积层的潜在储层包括：（1）积聚在斗拱状的远侧楔形中；（2）冲积层与碳酸盐滑坡碎屑的大量交织；（3）电镀；（4）与碳酸盐角砾岩精细混合。我们估计潜在的推土楔的最大体积约为105立方米，这表明其他列出的储层代表了冲刷物质的更多储量，与沿ML侵蚀北部边缘的滑坡碎屑和冲积物的混合外观一致。（6）运动波行为。DH的纵向轮廓像一个破碎波，其陡峭的前缘在上坡方向逐渐变细。这种轮廓类似于其他地方的波浪状脉冲，包括自然现象，如泥石流[46]。通常，当更快移动的尾随物料超过滑动或流动物料的前缘时，就会出现这种几何形状。DH中至少存在一个陡倾的反向断层，这支持了这样一个前提，即在跳动结束之前，前缘相对于尾随的材料变慢了，从而在滑动块的这些部分之间产生压缩。DH中此特征出现的可能解释包括（1）由于在DH之前被动冲积楔的推土而抵抗前进（图1，横断面G）和/或（2）逐渐降低坡度。冲积表面的坡度，这将影响到滑道前缘的速度在尾随材料遇到相同的下坡度之前降低。基于前面的观察和分析，我们假设三个基本过程来解释EVL的关键特征。这些过程的第一个也是最主要的是带能量回收的颗粒破裂（催化作用），我们设想控制滑坡在基岩峡谷区域通过期间的动力学。其他过程 适用于ML穿过MSC口处的冲积扇时，包括基质材料的掺入和冲积基质的局部液化。（1）建议的具有能量回收机制的颗粒破裂（催化）。我们将滑石块裂化解释为EVL中长期失控现象的关键过程，而不是仅仅作为进位的副产品，尤其是在基岩峡谷地区穿越时。我们认为，裂隙破碎是部分地干扰了跳动过程中正在移动的滑坡内部及其底部的摩擦能量消散过程。在这方面，所提出的机制与先前假设的机制大体相似，这些机制调用声学或机械的颗粒流机制来限制摩擦能量损失，并通过高频粒间和颗粒对基底的撞击来扩展大规模滑坡的作用范围[2，47-49]。 。从地质学的角度来看，这些颗粒流动机制的主要缺点是无法解释这些沉积物的质地[17]，特别是（1）颗粒流动模型要求在碰撞过程中碎屑保持完整，而现场证据表明碎屑在快速移动的滑坡内部甚至到了最细微的尺度，碎片化现象普遍存在[9，50]；（2）这些机制应产生富含圆形颗粒，正常分级的沉积物，和已知的地质颗粒流过程共有的其他纹理特征，例如浊流[51]和碎屑沉积物重力流[52]，但在EVL和其他长径滑坡中却基本不存在。与这些相反，本文提出的催化模型其他模型，与观察到的EVL和其他长期滑坡滑坡的纹理一致，并确实是由其激发的。在该模型中，施加到彼此接触并与基底接触的基岩层的动能通常会导致其破裂（而不是回弹），因此将瞬间储存在这些岩层中的弹性应变能以以下形式循环回滑坡球形冲击波。这样的冲击波将以约100-1200 m / s的速度在载玻片上快速传播[53，54]，远快于其最大跳动速度，为了使裂谷破坏的影响在迅速移动的滑坡的整个身体中迅速传播。为使这种拟议的机制起作用，冲击破裂必须在整个跳动过程中（或其主要部分）发生，而不仅是在罕见或奇异的发生期间（例如如Shreve [10]所建议的，对于黑鹰滑坡，滑坡在其初始骤降的底部的影响。虽然EVL最初从头皮开始暴跌，但一些滑坡角砾岩破裂（或沿现有不连续面的交界）可能会发生，但小规模滑坡和崩塌的性质告诉我们，在没有其他过程的情况下，这种初始运动阶段会导致源坡脚下的混合和未分级碎石块。保留ESV的前carp地层和逆向坡度，意味着从事件开始就沿着滑坡的底部进行了另一次（远没有那么混乱）的过程。我们设想将移动滑动块体的集中基底碎裂作为这种机制。在这种处理中，我们认为拟议的催化作用是通过对等式（3）中的抵抗项进行修改来发挥作用的，该方程式表示滑坡块滑移时的能量耗散。如果以每米为单位（例如工作时）放置其床。为了进行量化，我们通过将假设的破损引起的冲击的脉冲能量分解为相对于行进方向的三个垂直轴（垂直，横向和纵向）来解决此问题（图5（b））。与在机械颗粒流模拟中由颗粒碰撞产生的影响相似[2，47–49]，我们设想脉冲的垂直分量的作用是减小滑坡在其床面上的有效法向力，从而减小有效摩擦力。滑坡系数。侧向分量又起到潜在地垂直于移动方向散布碎屑的作用。纵向分量的作用是相对于质心加速滑坡的前缘并减慢滑坡的后缘，从而导致前缘的跳动长度增加，并在纵向上扩展碎屑片。摩擦损耗ε取决于诸如碎裂的厚度，速度，岩石强度和岩体膨胀等因素。尽管此处未进行处理，但我们预计劈裂的效率会随速度和基础载荷而增加，而随岩石强度的增加而降低。因此，重力和重力较低的滑坡应比地球上的滑坡效率低，这是因为速度和基础载荷降低，这与火星滑坡的观测行为一致[55]。对于ε=0⁠的端部情况，方程简化了基本的斜面块分析。对于ε> 0的任何值，需要额外的系数来说明与玻片块的缩孔相关的体积变化（25％的体积增加除以六个基本方向）。因此，ε的理论最大值略大于1。根据图5（b）的推论，我们预计破裂岩石碎屑产生的压力波会扩大运动碎屑的基础部分，就像声波和碰撞过程在不碎粒流的底部附近引起膨胀一样[2，47-49]。的确，考虑到在快速移动的滑坡底部附近发生的多种晶粒相互作用，无碎片的晶粒碰撞及其相关现象很可能以某种辅助方式促进了这些大质量运动的机理，这一结论也许得到了亚圆角碎屑的支持。除了解释EVL的质地和详细的运动学之外，基础碎裂机制还有助于解释所观察到的岩石滑坡限制之外的飞溅现象。这是因为，催化作用机制及其相关的快速晶粒运动预计主要发生在运动滑坡的厚而中心的底部，而不是在滑坡和滑坡的下方。（3）支持性观察。为了使分解模型起作用，冲击破裂必须在跳动的整个过程中（或其主要部分）发生，而不仅是在罕见或奇异的事件中发生，例如滑动块在其初始插入点的冲击。除了EVL的结构特征外，还可以从矿物加工和集料测试领域以及其他长粒滑坡滑坡的沉积物中获得对催化模型的支持。特别：因此，将机制的作用范围扩大到更平坦的坡度和更低的速度从其他长粒滑坡滑坡的微观纹理观测结果为断陷机制提供了额外的支持（5）强度考虑因素。除了能源方面的考虑外，还必须证明EVL的组成碎石可以合理地在移动的滑坡环境中经历撞击破碎。碎裂强度受基岩不连续强度，完整岩石强度和矿物硬度的控制。由于冲击破碎是一个动态过程，因此动态岩石强度是确定该过程是否可能在移动滑坡中合理发生的最重要参数。表9 [58-65]中概述的石灰石数据表明：（1）石灰石的压缩强度最高，强度值比剪切或拉伸强度高一到两个数量级。动态抗压强度更大，随冲击载荷线性增加[60，65]（2）石灰石的静态和动态抗剪强度大小相似，动态强度超过静态值不超过25％[61] （3）石灰岩的动，静态拉伸强度大致相等[62]（4）如所预期的，石灰岩间断面的剪切强度非常低，比完整岩石的剪切强度低大约一两个数量级[58]压缩强度最大，强度值比剪切或拉伸强度高一到两个数量级。动态抗压强度更高，随冲击载荷线性增加[60，65]石灰石的静态和动态抗剪强度大小相似，动态强度超过静态值不超过25％[61]石灰石的动态和静态抗拉强度大致相当[62]石灰岩间断的强度非常低，大约比完整岩石的强度低一到两个数量级[58]。碎石破碎需要施加超过组成碎屑最小强度的冲击力。因此，基于先前的强度等级，我们推测碎裂将首先涉及沿先前存在的不连续性对岩体进行分叉处理，然后通过剪切或拉伸破坏使完整的碎石破碎。在滑坡迅速移动的情况下，切向/掠过的冲击预计会导致剪切破坏，假设拉伸破坏是通过足够高的能使岩石垂直于冲击载荷“分裂”的劈裂冲击而发生的。后者的破坏模式类似于标准巴西抗拉强度试验[66]。石灰石由于剪切或拉伸断裂而导致的动态破坏将导致在目标滑石上施加至少4 MPa的冲击压力，这在快速移动的滑坡内部很容易实现。为了说明这一点，我们考虑以下假设：1千克碎屑以40 m / s的相对速度以0.1 s的接触时间撞击另一个岩石碎片，产生400 N的冲击力。 1 cm2导致每单位面积的力为400 N / 0.0001 m2或4 MPa。如果板块彼此碰撞或在撞击后从基板反弹，则施加的力/面积将是该值的两倍。碎裂碎片的产生更有可能是由大量碎屑与固定基底（尤其是基岩）之间的基底接触处捕获的单个碎裂的局部压力集中驱动的。（6）韧性考虑因素。摇滚优势 例如抗张强度和剪切强度，是衡量其抗脆性破坏的一种方法。岩石抵抗脆性破坏的另一种方法是岩石在裂缝扩展过程中吸收的能量，称为材料韧性。洛杉矶耐磨性（LAA）测试是评估岩石韧性的标准测试方法。对于粗骨料（> 19毫米），该测试包括在70厘米直径的滚筒中将10千克干燥物料与12个重5千克的钢球一起旋转30到33 rpm [1000] [67]。鼓中的鳍片抬起岩石和钢球，使它们跌落到下面的物料上，从而产生冲击粉碎效果。在规定的转数之后，将内容物除去，筛分骨料部分以除去所有小于1.7毫米的材料，其余的则称重。最终重量除以10公斤可得出样品的损耗。通常在LAA设备中使用的0.42公斤钢球达到的峰值速度约为3.3 m / s或更小，自由落体距离约为55厘米，冲击能量较大约为20J。已公布的LAA对石灰石和白云石的测试结果表明，经过1000次循环后，这些材料会遭受显着的磨损，磨损率范围为24％至36％[67，68]。考虑到EVL的速度要高得多（通常超过40 m / s），并且行进距离较长（在崎，不平的裸露基岩上超过一公里），因此可能会累积数千个能量超过20 J的冲击组成碎片。因此，从韧性的角度来看，LAA试验的结果表明，在跳动过程中，移动滑坡中石灰岩和白云岩类型的撞击破碎的可能性很高。（7）滞后效应。由于微裂纹在受影响材料中的积累，长时间的循环载荷会降低岩石强度。对于所有岩石类型，测试方法和破坏类型，Cerfontaine和Collin [69]报告说，岩石强度随着载荷循环次数的增加而稳定降低，在103次载荷循环后，强度下降了约15％，在106次循环后，强度下降了22％。 。对于石灰岩的特殊情况，Haimson [63]报告称，在施加103至105个载荷循环后，抗拉强度降低了50％至75％，抗压强度降低了25％至30％。Kamonphet等。[70]报告在10个剪切周期内石灰石的剪切强度没有明显降低，而Okada和Naya [64]报告说在施加103个载荷周期后凝灰岩和人造砂岩的剪切强度降低了15％至20％（表9）。尽管很难判断在快速移动的滑坡中劈裂所经历的荷载循环次数，但在崎landscape的地形上运动会在受影响的劈裂中引起许多荷载循环，每米行程可能多达一个或更多。在40-50 m / s的速度下，这意味着每秒40到50个循环，并且每公里行程累积104到105个负载循环。快速移动的滑坡的地震记录已记录了40-50 Hz范围内的频率[71]，支持这样的假设：在这种情况下，载荷循环会迅速累积。（8）微观结构考量。在极端活跃的滑坡环境中，碎裂之后是单个矿物颗粒的破裂[9，50]。在常见的岩石耐久性测试中，例如洛杉矶（ASTM C 535，LAA）和磨机磨损测试，该过程由矿物硬度控制[67]。不知道此过程是否在EVL中进行。但是，该过程在其他示例中是已知的，包括加利福尼亚南部的马丁内斯山[9]和钙华[50]滑坡。在这两个示例中，岩石碎屑角砾岩细小，连贯的岩石学分析都来自这些滑坡的底部，它们捕获了单个矿物颗粒的“冻结帧”图像，并在细颗粒状的基质中破碎和分散。这些岩相学分析的图像为这些滑坡在工作中的粉碎过程的功能提供了直观的指导，并有助于告知本文所设想的粉碎机制。（9）Cataclasis模型在尤里卡山谷滑坡中的应用。为了测试提出的EVL的分解模型，我们将公式（8），（10）和（13）应用于从Google Earth地形得出的ML和PML的简化跳动路径几何形状（表10）。如表10所示，用于ML的模型跳动路径几何结构由七个已知长度和倾斜角度的段组成，而利用八个段对PML建模，以识别其更弯曲的行进路径。ML和PML的源块分别细分为9个子块（在源斜率上从最低到最高编号），他们通过跳动路径时，在电子表格计算中会遵循其重心加速度，速度和行进距离。对于PML，平行于坡度的初始块尺寸为31 m，对于ML计算，则为75 m。图4显示了建模的行进路径几何形状，主要断点的位置以及每个子区块的质心的计算的开始和结束位置。催化模型的应用需要计算每个串联滑梯的可变加速度滑块的大小取决于重力加​​速度，倾斜角度以及相对于其他滑块的位置。除了在斜坡过渡附近 块1始终经历最大的加速度（方程式（10）），而尾随的块始终经历最低的加速度（方程式（13）），而中间的块则经历中间值，具体取决于在任何给定时间运动的块数（表11）。九段模拟的开始使用了表11第一行所示的加速度。在跳动模拟期间，具有最低加速度的尾随块首先停止。当原始尾随块（块9）停止运行时，其余八个块的加速度将移至表中的第二行，依此类推，直到只有块1保持运动。在仿真的这一点上，催化作用机制处于“关闭”状态，并且允许块1使用未经修改的摩擦系数μ（等于0.5）滑动至停止状态。（10）适用于次要凸角。表12显示了将催化模型应用于PML的结果。表格中显示的模型结果适用效率系数ε=0.88⁠，这与整套观察到和推断出的矿床特征提供了最佳匹配。如表10所示，小叶“上S骨”的顶部对应于卡拉拉组与上覆的波南萨国王组的上部接触。选择该位置是因为卡拉拉组几乎包括了整个矿床。尽管PML中几乎没有什么独特的灰色Bonanza King层灰岩，计算中包括一个简短的附加“牺牲”坡度部分，以说明一次必须已从次要裂口被侵蚀去除的峡谷中占据峡谷区域上坡的滑移材料的质量。如第二列所示从表12中可以看出，九个PML起始块的峰值速度在26到48 m / s的范围内，该峰值速度是在head头下方的“初始插入量”的底部计算得出的。这些速度估计值达到或超过了滑坡碎片爬升至初始冲刺底部的35 m高相对坡度并进入相邻流域所需的最小速度26 m / s。如果没有催化作用机制或其他降低滑石有效摩擦的方法，这些滑动材料都不会超出风隙并进入相邻的分水岭。作为参考，图4显示了沿其跳动路径的各个点处的次瓣前缘的计算速度。通常与现场证据一致。具体而言，催化模型可预测远端锥形的几何形状，与观察结果一致。通过假定最初31 m长的滑动块在跳动期间经历纵向扩展以保持与相邻块的接触，可以从模型中获得最终轮廓几何形状。相邻块的端点之间的距离越远，则沉积物越稀薄。（11）适用于主瓣。通过将催化模型应用到PML所获得的良好结果表明，该模型合理地适用于通过基岩峡谷平移的长径滑坡。将催化模型应用到ML的跳动中，得出以下发现：（1）通过催化模型将白色石灰岩标记床从山腰运送到峡谷口以及更远的地方需要高效系数-与应用于PML的0.88值相比，接近1。更高的效率因数的理由包括（a）ML碎屑的平均厚度越大，以及（b）ML在跳动期间积累的整体变形程度越小。后一种解释是基于在ML部位暴露的保存完好的头皮地层与在次瓣内部暴露的主要褶皱和变形之间的对比（2）。必须将包含白色标记床的材料推过峡谷的入口。计算表明，该缺失斜坡段的后缘停在峡谷口上游近300 m处，如表13和图4所示。与应用于PML的0.88值相比，该模型需要一个接近1的高效率因子。更高的效率因数的理由包括（a）ML碎屑的平均厚度较大，以及（b）ML在跳动期间积累的整体变形程度较小。后一种解释是基于在ML部位暴露的保存完好的头皮地层与在小叶内部暴露的主要折叠和变形之间的对比所产生的。包含白色标记床的材料经过峡谷的入口。计算表明，该丢失的斜坡部分的后缘停在峡谷口上游近300 m处，如表13和图4所示。但是，ML在穿过冲积扇时具有非凡的机动性，需要根据现有的现场证据做出另一种解释，如下所述。（12）混合机制。当ML离开源峡谷时，它的行程比分解模型预测的行程大约远三倍（并且比典型的摩擦系数所允许的距离还远得多），同时明显推土并在其路径中合并了160万立方米的冲积层。在此过程中，它形成了向远端凸起的轮廓，从而使其与PML的锥形远端区别开来。根据这些观察结果，我们认为催化作用机制不可能控制ML的最终跳动阶段。代替，我们假设快速移动的滑坡碎屑突然施加载荷会导致MSC口附近的冲积层液化，从而触发了控制滑坡后续运动的过程。在更温带的环境中，包括欧洲，加拿大，日本和美国西北太平洋地区，发生了大型的快速滑坡[27，72]。干旱和半干旱地区的一些长期滑坡滑坡沉积物也包含本文提出的同沉积和后沉积碎石堤坝形式的基底液化类型的证据。来自加利福尼亚州和内华达州的例子包括黑鹰，埃尔卡皮坦，锡坎平，石灰华和瓦莱奇托滑坡[9，73]。三个现场观测结果为ML的最终运动阶段提供了液化假设：（1）在MSC口附近沿其侵蚀边缘暴露的泥流状纹理存在；（2）西北部存在碎屑堤防。小叶，以及（3）是否存在位于DH西北部的异常沉积物，以Qo单位表示？在图1上，我们将基底液化的引用证据归因于快速加载以及快速滑动的滑坡碎片（从MSC出来）在冲积基底的局部饱和边缘上施加的主要剪切应力。根据估计的山前冲刷深度，液化事件显然是在峡谷口下方原始表面的上10 m内引发的。我们推测，该深度与由MSC散发出来的古地下水位的位置相吻合，MSC来自沿边界拓宽的断层（预计将充当无水层）的间歇性水流和渗流和泉水，可能由较冷的和/或滑坡发生时大约100至120 ka的湿润条件（图3）。我们预计这种近地表水沿山脉前沿位于相对较窄的带内，就像盆地和山脉省沿山脉边界断层的情况通常如此。给定DH的面积为27公顷，液化层的平均厚度为0.3 m，我们估计该工艺需要夹带约80,000 m3的饱和冲积层。假设碎片离开主峡谷时宽度为300 m，开挖深度为10 m，对于沿范围前沿的润湿区域，这将对应于约27 m的宽度。该宽度与Google Earth对沿范围断层的沿河断层带宽度的Google Earth测量结果（例如，犹他州的Wasatch Front和南加州的San Andreas断层带）非常相关。我们设想，一旦被带走，ML的快速下坡运动就会使湿润的物料沿着碎屑桩的底部散布，并通过搅动将其保持液化状态，并持续较短的跳动时间。约翰逊[73]引用了一种类似的机制来解释南加州黑鹰滑坡的异常长跳动，并指出：“……黑鹰滑坡可能已经穿过冲积层，形成了两层复合泥石流，其中厚厚，可能很低-流动的大理石角砾岩层骑在相对较薄的地方，在Blackhawk滑坡和上面列出的其他几个示例中，堤坝相对常见。ML暴露中相对没有碎屑堤防可能与以下事实有关：该山体滑坡发生在干燥气候中，比上述情况更小，更薄，更轻，从而限制了液化物料的产生和可利用的超压将流体注入上方的角砾岩中。可替代地，在运动停止时暴露在推土的远侧楔形物中的液化冲积材料可能已经经历了横向通风，而不是侵入上覆的角砾岩中以形成碎石堤。8号位置的明显碎屑堤（图1）为滑坡发生时峡谷口附近浅层地下水条件的存在提供了佐证。形成堤坝的材料似乎由与断层有关的钙华沉积物组成。根据这一证据，我们推测滑坡在时间上对应于范围性额叶断层的活跃渗漏/春季活动期，并且滑坡在其覆盖附近的额层断层时并入了饱和的钙华物质。 ML安置期间的液化也发生在远离山腰的地方。Wrucke和Corbett [13]绘制了Qo？单位（图1）作为沙丘沉积物。我们的地貌解释是，该特征可能代表运动停止后从DH脚趾流出的液化冲积层的流出。Qo？该矿床的表面积约为22公顷，体积约为350,000立方米。因此，这将代表ML在冲积扇下降时冲刷的冲积量的大约五分之一。尽管缺乏良好的野外曝晒以及最近的冲积层和浮沙使它的解释变得复杂，但该单元显然主要由冲积材料组成，而不是浮沙。这些沉积特征与沉积物的流状形式一起，为流出解释提供了初步的支持。对该特征的一种可能的替代解释是，它代表了可追溯到滑坡发生的遗迹冲积层，并通过DH的掩护作用得以保留，这往往使上坡径流偏向山谷底部。在这种解释中，航空影像中沉积物的流状外观是由于沉积物边缘周围的侵蚀性通道的偶然布置而产生的。该地区侵蚀的原因包括与滑坡有关的干扰对源流域，构造和气候因素的挥之不去的影响，尽管最终形成主瓣的碎屑到达目的地时移动速度超过40 m / s。 MSC的入口，其速度仍然不足以传送碎片1。在没有一些特殊的减少摩擦的材料或工艺的情况下，冲积风扇向下7公里。例如，分解模型仅预测山前下方还有约500 m的跳动（表13，图4）。表13详细介绍了隐性液化事件对ML退出时的跳动的影响。 MSC。此分析从第1块至第6块离开源峡谷入口时的计算速度开始（基于催化模型的应用，第7块至第9块代表的材料在山前上游停留在峡谷中） 。计算的其他输入包括冲积扇面的坡度和块的估计最终位置（表13；图4，插入A），它们被用作质量分布的代理，每个块分配相等的面积。分析得出的结果是，穿过冲积扇的砖块的有效摩擦系数为0.13至0.16（表13），相当于大约7至9度的滑动摩擦角，前缘最大，后缘最小。前沿材料的较高摩擦系数归因于ML在其穿过冲积扇时在ML之前冲积沉积物的推土所引起的阻力，尽管此处计算出的计算出的滑动摩擦系数相当低，但仍要大得多比已知在主要地震事件中经历液化引起的横向扩展的斜坡的倾斜度低，其倾斜度可低至1度[74]。残留摩擦角为7至9度，表明液化材料的残余强度约为50至60 kPa，与已知的土壤液化事件上限的文献值一致[75]。总之，我们推断，一旦ML它从MSC的入口处冲刷到冲积扇上，然后液化基材，并以快速，高强度的侧向传播方式横穿了风扇。EVL的整体跳动机制由基岩峡谷地区的分解模型与冲积扇上的液化/侧向扩展混合而成，已经提出或可以设想其他的位移机制来解释长跳动和其他冲动特征EVL，其他类似Blackhawk的滑坡，以及其他长期损坏的滑坡[2，8，10，16，17，20，27，29，47，49，55，72，73]。我们在这里简要地研究了这些与EVL相关的替代假设中最相关的假设，包括（1）在富含粘土的基底上滑动[8]，（2）水下填充[8]，（3）空气层润滑[10] ]，（4）塑料流[55]和（5）在冻结的基板上滑动。拟议的机械和声学颗粒流动模型[2，47，49，54]已经在本次讨论中进行了处理，在此不再赘述。Watkins[8]提出了一种利用基础润滑来润滑EVL主瓣的机制由水合粘土材料制成。该假设的基础是（1）在ASTER遥感数据中可能识别滑坡底部的水合物质，以及（2）保留沉积物中裸露的head皮地层和其他地质结构。沃特金斯[8]利用ASTER卫星收集的遥感数据评估了EVL附近是否存在粘土矿物。表14显示了14个ASTER波段的光谱范围和空间分辨率[76]。沃特金斯[8]引用了ASTER 4：8谱带比图像，以识别EVL中潜在的水合物质（即粘土），解释了图像中ML趾部的浅色弧形，以反映水合粘土沿硅藻土的暴露。暴露的存款基础。根据Gomez和Lagacherie的报告[77]，常见的粘土矿物会在2200 nm附近吸收一条吸收带（ASTER带6），而碳酸钙会在2340 nm附近产生一条吸收带（ASTER带8；表14）。由于波段8的反射率对于富含碳酸盐的材料而言较低，因此ASTER波段4：8比率图像不能很好地用于识别粘土矿物，但对于富含碳酸盐的区域来说会显得明亮。该结论与在EVL附近收集的ASTER带比4：8图像的外观一致。在这里，富含碳酸盐岩的上部伍德峡谷，卡拉拉和富矿王岩层下的斜坡都呈现出淡淡的色调，而由Zabriskie石英岩层岩下的斜坡区域显得较暗，反映了这些岩层的相对碳酸盐含量[31]。基于这些观察结果，我们得出结论，沃特金斯[8]引用的ASTER 4：8图像的浅色区域指示了水合粘土矿物在地下的区域，包括ML趾部的浅色弧。事实突出了富含裸露碳酸盐材料的地区。我们用较薄的富含二氧化硅的风沙粉饰面来解释ML平衡的较暗阴影。虽然我们同意Watkins [8]的观点，但carp皮地层的保存和EVL ML的结构与作为基础润滑机制，我们不同意粘土在其跳动中发挥了重要作用。除了遥感数据中缺乏对粘土的支持外，我们对滑坡的野外勘测没有发现该地区粘土沉积的视觉证据，而且我们的XRD数据（表7）表明滑坡碎片本身几乎完全缺乏粘土。 。此外，粘土只有在饱和并缓慢剪切后才能形成可靠的润滑剂[78]。基于这些观察和考虑，我们得出结论，黏土润滑不是安置EVL的可行机制。沃特金斯[8]还提出了将水下填充物作为EVL的水合粘土材料基础润滑的一种潜在替代方法（或辅助方法），理由是其长期存在的行为和ML的形态，“类似于某些水下滑坡的情况。 ” 由于多种原因，该假设存在问题。显然，水下条件不是大型快速滑坡长期跳动的必要先决条件。此外，各种陆地和陆地外滑坡都具有类似EVL的黑鹰状形态，这也不能诊断出水下沉积物（图2）。此外，由于缺乏整个第四纪时期尤里卡河谷中常备水体的证据，因此，EVL的水下安置存在问题。没有湖床沉积物或诸如海岸线特征之类的地貌证据都支持第四纪时期尤里卡河谷中存在站立湖泊的假说[37]。相比之下，附近的欧文斯谷和死亡谷保留着迄今估计为MIS 6至12 [80，81]的海岸线特征，比EVL的估计最大年龄大得多。第四纪时期，尤里卡河谷缺乏持久的水体，这是由于其位于因约山和内华达山脉的3000 m至4000 m高峰的雨影中，以及高高的门槛高度阻止了相邻水源丰富的水流入分水岭。山谷中最近的持久湖泊可追溯到上新世中期，约3.5 Ma，这可能反映了当时的古欧文斯河流入山谷[37]。基于这些观察的权重，我们认为水下水位是EVL的不可持续的假设。Shreve [10]提出的空气层润滑假设解释了南加州黑鹰滑坡及其形态类似物的长跳动及其他特性。一个流行的假设，经常出现在地质入门书中[82-85]。对黑鹰状滑坡的空气层假说的反对意见包括在几乎没有空气的火星和真正没有空气的谷神星上存在形态相似的沉积物（图2）以及一系列其他质地和物理问题[17，73]。除了这些观察，我们还对EVL包括以下特定限制：（1）缺少使滑坡碎片以足够的速度到达冲积扇的速度到达峡谷口的机制。碎石的休止角通常在35至45°的范围内，而源区与MSC的入口之间的夹角为21°。因此，从运动开始就禁止某些增强移动性的机制的作用，滑坡碎片根本不应该离开源峡谷。约翰逊[73]认识到这个问题对黑鹰滑坡本身是有问题的。（2）缺乏明显的发射坡道。ML沿着MSC滑行，并在其口处降落到冲积扇上，而没有遇到明显的地形台阶，该台阶使它升空后可以捕获并压缩下面的空气层。（3）冲积基质的冲刷伴随着主瓣的进入，阻止了快速移动的碎屑使风扇“像气垫船一样”下降。空气层润滑模型设想在风扇通过时在冲积表面和滑坡碎屑之间施加压缩气垫，该概念与快速移动的角砾岩冲刷冲积表面的冲刷不一致。允许滑坡碎片以足够的速度到达峡谷的入口，然后将其发射到冲积扇上。碎石的休止角通常在35至45°的范围内，而源区与MSC的入口之间的夹角为21°。因此，从运动开始就禁止某些增强移动性的机制，滑坡碎片根本不应该离开源峡谷。约翰逊[73]认识到这个问题对黑鹰山体滑坡本身是有问题的。ML沿着MSC向下行驶，并在其口处降落到冲积扇上，而没有遇到明显的地形台阶，该台阶使它升空后可以捕获并压缩下面的空气层。冲积层的冲刷伴随着主瓣的进入，阻止了迅速移动的碎屑使风扇“像气垫船一样”下降。空气层润滑模型设想在风扇通过风扇时在冲积表面和滑坡碎屑之间施加压缩气垫，这一概念与快速移动的角砾岩冲刷冲积表面的冲刷不一致。基于这些观察的权重，我们认为空气层润滑也代表了EVL的不可持续假设。塑性行为是许多常见日用物质的特征，例如油漆，番茄酱和牙膏。还提出了解释某些地质起源的物质的流动的方法，包括熔岩流和泥石流。许多长期滑坡所表现出的流体状和片状几何形状都提示它们也表现出整体塑性流动特性[55]。当这些材料承受的基础剪应力超过某些与材料有关的“屈服应力”时，会经历流动[30]。对于滑坡含水量较高的情况，这种行为既合理又可证明[20，44]。但是，如果是由干燥岩石组成的长期崩塌滑坡，突然的内部不连续性的存在和海carp树皮地层的保存与经典的流动概念相抵触，并主张具有局部内部变形的基底滑动。方程式（20）的意义在于，倾斜角σ⁠越大，则流量厚度，D⁠。为了测试方程式（20）是否适用于EVL，我们结合现场测量结果对沉积物厚度D？和沿沉积物边缘沿移动方向σ⁠的地面坡度进行了9次测量（图4）。和Google Earth的地形剖面，沿着与滑动边缘平行的50 m长的样线。这些数据的曲线图显示出相当大的分散性，但通常会在沉积物厚度和表面斜率之间产生正相关关系（图4，插图B，虚线）。如果滑坡起塑性作用，则这种趋势与预期相反（图4中的虚线，插入物B，假定屈服强度为8,500 Pa进行计算）。因此，EVL拒绝采用塑性流动假设，因为它无法解释其内部结构的细节及其详细的几何形状。如图3所示，EVL可能发生在温度较低且可能比温度高的时候当前时期。因此，我们通过在冷冻基板上滑动来评估可用于安置的证据。尽管北美大部分地区与冰川事件有关，但存在着严峻的含义，尤里卡河谷位于最后一次冰川最大期（MIS 2）期间，位于北美公认的永久性冻土南部界限的南端[87]。此外，在分配给滑坡的时间内，死亡谷的最高温度通常比上次冰河最高时期高约10°C（图3），从而进一步降低了在冰覆盖的表面或埋藏的永久冻土层上进行定位的可能性。在ML放置期间推断的冲积层深10 m的开挖还可以防止在罕见的冰冻或暴风雪之后在暂时的冰或雪幔表面上滑动。因此，我们认为在ML上放置冰块的可能性不大。在大约60和120 ka之间，一块寒武纪的石灰岩块体，其体积超过500万立方米，沿其平面的不连续面在其最后的源头处分离。机会范围并迅速加速下坡。角砾岩的运动块在其初始下降的底部分成两个不等的裂片。较小的瓣叶约占失败块的40％，向南移动并停在侧峡谷中。较大的波瓣穿过山脊的北部，经过了主要峡谷的全长，其大部分最终都在河口处冲积到冲积扇上。到达MSC的入口后，主瓣沿冲积扇的长度开挖了约10m的深沟，并在其团块中掺入了约160万立方米的置换物质，使远端堆肥变厚并变宽。伴随着滑坡从山坡上脱离，并穿过基岩峡谷地区。并不是滑坡过程的简单副产品，我们将滑石的裂变解释为反映了穿越岩石斜坡和峡谷的大型快速滑坡运动背后的关键过程。这里设想的物理过程涉及将破碎碎屑的弹性能量回收到移动的碎屑中，从而大大提高了滑坡的移动性。原则上，此过程应在任何地面或地球外环境中起作用，在这种情况下，组成岩体在安装过程中可能会发生脆性，冲击驱动的拉伸或剪切破坏。当ML离开MSC时，遇到了弱得多的局部湿润，冲积基质在快速加载和剪切作用下屈服于液化，促使运动的第二阶段。当碎片从MSC离开时，从催化作用机制接手，基底液化将快速移动的碎屑的延伸范围扩大到仅通过分解机理就可能达到的距离约一公里。没有现场证据支持替代机制，例如在饱和粘土，冻结地面或空气的基底层上滑动。现场证据还排除了ML的水下入渗，以塑性流动入渗或通过任何需要组成碎屑保持其完整性的机制（例如声音或机械谷物流动）来动员滑坡的现象，这些发现为更好地解决这些问题提供了一种手段预测通常伴随大规模边坡破坏的未来长期滑坡滑坡的范围。这项研究提供的关键见解包括：认识到故障源块的尺寸，跳动轨道的几何形状，基质的性质在控制大型，快速边坡破坏所经历的跳动中都起着重要作用，因此，它们均是评估未来大规模大规模运动带来的风险的重要因素。面对大型快速滑坡在其基础上施加的极其猛烈的能量，最弱的材料的行为占了上风。在岩石表面上行驶时，是由碎屑的强度来决定过程的，但是当碎屑遇到较弱的基质（如饱和土壤）时，则决定了土壤的性质。结果是地质，几何和环境在大多数情况下，合格的现场人员应该可以访问和量化本文所讨论的因素。在极端敏感的地方，例如在人口众多中心（或位于人口中心上游）的崎water分水岭，这种调查似乎是有必要的。利用这一机会的关键是成功地阻止了历史和地质记录中其他受约束的长期滑坡滑坡的发生。作者声明，本文的发表没有利益冲突。ESi（Engineering Systems Inc.） Exponent，Inc.为现场工作和实验室测试提供了财务支持。作者要感谢Keith Shaller，Steve Okubo，Greg Ferrand和Jeff Knott的宝贵帮助，以及Jeff Knott，Jeffrey Keaton，Ann Shaller，Keith Shaller，Pravi Shrestha和Kristina Cydzik的有益社论评论和讨论。利用这一机会的关键是成功地阻止了历史和地质记录中其他受约束的长期滑坡滑坡的发生。作者声明，本文的发表没有利益冲突。ESi（Engineering Systems Inc.） Exponent，Inc.为现场工作和实验室测试提供了财务支持。作者要感谢Keith Shaller，Steve Okubo，Greg Ferrand和Jeff Knott的宝贵帮助，以及Jeff Knott，Jeffrey Keaton，Ann Shaller，Keith Shaller，Pravi Shrestha和Kristina Cydzik的有益社论评论和讨论。利用这一机会的关键是成功地阻止了历史和地质记录中其他受约束的长期滑坡滑坡的发生。作者声明，本文的发表没有利益冲突。ESi（Engineering Systems Inc.） Exponent，Inc.为现场工作和实验室测试提供了财务支持。作者要感谢Keith Shaller，Steve Okubo，Greg Ferrand和Jeff Knott的宝贵帮助，以及Jeff Knott，Jeffrey Keaton，Ann Shaller，Keith Shaller，Pravi Shrestha和Kristina Cydzik的有益社论评论和讨论。ESi（工程系统公司）和Exponent，Inc.为现场工作和实验室测试提供了财务支持。作者要感谢Keith Shaller，Steve Okubo，Greg Ferrand和Jeff Knott的宝贵帮助，以及Jeff Knott，Jeffrey Keaton，Ann Shaller，Keith Shaller，Pravi Shrestha和Kristina Cydzik的有益社论评论和讨论。ESi（工程系统公司）和Exponent，Inc.为现场工作和实验室测试提供了财务支持。作者要感谢Keith Shaller，Steve Okubo，Greg Ferrand和Jeff Knott的宝贵协助，以及Jeff Knott，Jeffrey Keaton，Ann Shaller，Keith Shaller，Pravi Shrestha和Kristina Cydzik的有益社论评论和讨论。