Cyclic shear zone cataclasis and sintering during lava dome extrusion: Insights from Chaos Crags, Lassen Volcanic Center (USA)

doi:10.1016/j.jvolgeores.2020.106935

Journal of Volcanology and Geothermal Research

Volume 401, 1 September 2020, 106935

https://doi.org/10.1016/j.jvolgeores.2020.106935 Get rights and content

Highlights

•
A syn-eruptive shear zone (gouge and cataclasites) envelopes Dome C at Chaos Crags.
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Shear zone cataclasites have lost porosity and lithified by solid-state sintering.
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Magma ascent rates <10 m/day are required to form observed cataclasites.
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Shear zone permeability loss and strengthening hinder outgassing and magma ascent.
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Cyclic fracturing and sintering can dictate lava extrusion vs. explosivity.

Abstract

The ascent and extrusion of crystal-rich magma is commonly facilitated by deformation partitioned within annular, conduit-parallel shear zones. The physical properties and textures of the shear zone materials, where exposed at surface, provide a record of ascent and eruption dynamics. We describe the shear zone developed in Dome C, part of Chaos Crags in the Lassen Volcanic Center (California, USA). The extruded shear zone comprises volcanic fault gouge and variably densified cataclasites. The competent cataclasites evidence deep-seated gouge production followed by gouge densification within the conduit on the timescale of lava dome ascent. Textural, geochemical and mineralogical data identify solid-state sintering as the densification mechanism. At the temperatures and pressures in the volcanic conduit, solid-state sintering causes rapid porosity and permeability loss within the gouge and concomitant material strengthening. Longer dwell times (i.e., slower ascent) allow for more sintering, producing stronger, denser and less permeable cataclasites. At Chaos Crags, we use the extent of sintering, quantified by residual porosity, to recover minimum in-conduit dwell times necessary to produce the observed cataclasites. Our analysis of the Dome C cataclasites suggests a maximum linear ascent rate of 10 m/day and a minimum ascent time of 100 days. We evaluate the consequences of shear zone lithification by solid-state sintering for the eruption of other crystal-rich, glass-poor magmas. Chaos Crags cataclasites preserve evidence of multiple cycles of fracturing, cataclasis and (re-)sintering suggesting a mechanism for transitions between effusive and explosive phases of dome-building eruptions.

Introduction

The rate at which magma transits the crust has a strong influence on the magma's physical, chemical and transport properties, and can control the nature of eruption and the eruption products (Rutherford, 2008). Slow ascent rates can induce decompression-driven degassing and crystallization causing increases in magma viscosity and resulting in the formation of lava domes (Nakada et al., 1995b; Sparks, 1997; Voight et al., 1999; Sparks et al., 2000; Edmonds and Herd, 2007; Rutherford, 2008; Cashman et al., 2008; Husain et al., 2014). During particularly slow ascent of intermediate magmas (e.g., extrusion rates < 7 m³/s; Watts et al., 2002), extensive degassing and crystallization create strong, stiff magmas that favor brittle deformation rather than viscous flow (Sparks et al., 2000; Hale and Wadge, 2008; Pallister et al., 2008; Heap et al., 2016; Zorn et al., 2018).

Forced ascent of such magma causes extremely localized deformation at the interface with the surrounding wall rock where shear stresses are greatest (Hale and Wadge, 2008; Smith et al., 2011; Kennedy and Russell, 2012; Okumura et al., 2016). Strain localization is evidenced by the formation of an annular shear zone around the solidifying magma plug (Sparks et al., 2000; Watts et al., 2002; Cashman et al., 2008; Hale and Wadge, 2008; Holland et al., 2011; Kendrick et al., 2012; Lavallée et al., 2013; Pallister et al., 2013; Hornby et al., 2015; Wallace et al., 2019a). Further deformation sequestered in the shear zone facilitates transit of the plug over hundreds to thousands of meters to the surface (Cashman et al., 2008; Okumura and Kozono, 2017).

These processes produce high aspect ratio lava domes and spines (Sparks et al., 2000; Cashman et al., 2008; Heap et al., 2016) such as observed at Soufrière Hills (Montserrat, 1995–2010; Voight et al., 1999; Watts et al., 2002; Loughlin et al., 2010; Ryan et al., 2010), Mount St. Helens (USA, 2004–2008; Iverson et al., 2006; Scott et al., 2008; Dzurisin et al., 2015), Mount Unzen (Japan, 1991–1995; Nakada et al., 1995a, Nakada et al., 1999) and Santiaguito (Guatemala, 1922–present; Rose, 1972; Holland et al., 2011; Rhodes et al., 2018). Many of these lava domes are enveloped in cataclastic carapaces of variably densified volcanic fault gouge representative of the conduit shear zone (Nakada et al., 1995a; Watts et al., 2002; Iverson et al., 2006; Cashman et al., 2008; Kennedy and Russell, 2012; Pallister et al., 2013; Rhodes et al., 2018). The fault gouge results from fracturing of the coherent magma/lava, followed by cataclasis of the particles (i.e., comminution, translation and rotation; Engelder, 1974) and simultaneous mechanical compaction. The physical properties and microstructures of the cataclastic materials record information about magma ascent and eruption processes including the deformational processes governing magma ascent (e.g., Cashman et al., 2008; Kennedy et al., 2009; Kendrick et al., 2012; Pallister et al., 2013), the extent and implications of in-conduit alteration (e.g., Wallace et al., 2019a), and the efficiency of volcanic outgassing (e.g., Gaunt et al., 2014).

Here we describe the shear zone encasing a crystal-rich, glass-poor rhyodacitic lava dome (Dome C), part of Chaos Crags within the Lassen Volcanic Center (California, USA). The enveloping conduit-parallel shear zone is well-exposed by the partial collapse of the original lava dome, and the outcroppings reveal it to comprise unconsolidated gouge and variably competent cataclasites. Below we document the structural organization and textural properties of the Dome C cataclasites, as well as their microstructural, physical and mechanical properties. We use these observations and data on the Dome C shear zone materials to show that: (1) fracturing and cataclasis of the dacite at depth produced unconsolidated volcanic fault gouge, and (2) much of the gouge underwent solid-state sintering within the conduit to become the variably densified and lithified cataclasites observed at the surface. Solid-state sintering is a diffusion-driven process, akin to diffusion creep that causes crystalline particles to coalesce and results in densification (loss of porosity) and lithification (increase in competence/strength) (e.g., Rahaman, 2003). Here we show that solid-state sintering of the gouge must have occurred on the timescale of the dome-producing eruption. We conclude with microstructural evidence for re-fracturing of the sintered cataclasites at depth, indicating cycles of cataclasite reworking and re-sintering accompanied the extrusion process. These processes imply shear zone properties (i.e., permeability, porosity, strength) are highly transient and can modulate eruptive behavior during the eruption of crystal-rich, glass-poor lava domes.

Section snippets

Chaos Crags

Chaos Crags is within Lassen Volcanic National Park (California, USA) and is a part of the Lassen Volcanic Center, the southernmost volcanic center in the Cascades (Heiken and Eichelberger, 1980; Clynne, 1990). Chaos Crags is the youngest eruption in the Eagle Peak sequence, occurring 1103 ± 13 years B.P. (~850 CE; Clynne et al., 2008a) and contributing to the formation of the silicic Lassen dome field (Clynne and Muffler, 2010, Clynne and Muffler, 2017; Muffler and Clynne, 2015). Chaos Crags

Methods

The whole rock major element chemical compositions of samples of units D, C_Hi, C_Lo and G were determined by XRF analysis at ALS Geochemistry laboratory in Vancouver (BC, Canada), based on 2 g aliquots of each sample (Table 2). Replicate analysis of aliquots of sample L2 from unit C_Hi was used to establish analytical uncertainty. The mineral componentry of the same samples (Table 3) was determined by Rietveld refinement of X-ray diffraction spectra (Raudsepp et al., 1999).

Thin section billets

Geochemistry and mineralogy

The units D, G, C_Hi and C_Lo have common chemical compositions (Table 2) and modal mineralogy (Table 3). Mineralogically, the rocks comprise plagioclase (andesine, 40–45 wt%), high- (anorthoclase to sanidine) and low-temperature (microcline) alkali feldspars (20–25 wt%), SiO₂ polymorphs (quartz, 12–15 wt%; cristobalite, 4–9 wt%), and minor (5–8 wt%) other phases (cf. Table 3). The XRD spectra also suggest the presence of a small quantity (4–8 wt%) of amorphous material which can be amorphous

Discussion

The variably densified and lithified cataclasite units that make up the Dome C shear zone evidence a deep-seated gouge production event followed by the densification and lithification of the gouge within the conduit on the timescale of the eruption. The lithification process was so effective that it created cataclasites that are stronger and less permeable than the dome interior (Fig. 6). Identifying the relevant lithification mechanism, and the associated magnitudes and timescales of

Implications beyond Chaos Crags

The exposed shear zone at Dome C of Chaos Crags preserves evidence of solid-state sintering occurring within the hot volcanic conduit, leading to the densification and lithification of the gouge over hours to hundreds of days (Fig. 7b, c). Microstructures in the cataclasites also show that despite associated porosity loss and material strengthening, deformation continued to occur within the sintering portions of the shear zone.

In general, the properties of intra-conduit shear zones govern magma

Conclusion

The shear zone of Dome C at Chaos Crags comprises cataclastic units that preserve textural evidence of (1) gouge generation at depth, (2) syn-eruption densification and lithification of the shear zone by solid-state sintering, (3) deformation of competent, sintered cataclasites, despite their considerable strength, and (4) cyclical cataclasis and re-sintering of the shear zone within the conduit during the eruption (a period of hundreds of days). In previous models for the ascent of

CRediT authorship contribution statement

Amy G. Ryan: Conceptualization, Investigation, Formal analysis, Writing - original draft, Writing - review & editing, Visualization. Michael J. Heap: Conceptualization, Investigation, Writing - review & editing. James K. Russell: Conceptualization, Writing - review & editing, Supervision. Lori A. Kennedy: Resources, Writing - review & editing. Michael A. Clynne: Resources, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The work was permitted by the United States National Park Service (study number: LAVO-00050; permit number: LAVO-2019-SCI-0010), and was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants program (RGPIN-2018-03841; JKR). We thank Stephan Kolzenburg and Martin Harris for their help in the field, Fabian Wadsworth for providing us with the code for the permeability model from Wadsworth et al. (2016), and Elisabetta Pani for her help with Rietveld

Data availability

Data will be made available upon request.

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One block was taken from the tongue-shaped Chaos Jumbles collapse deposit (block CCC), and four blocks were taken from the altered carapace of the dome that now forms the collapse scar (blocks CC3, CC4A, CC4B, and CC10). The blocks from Chaos Crags, previously described by Ryan et al. (2020) and Heap et al. (2021b), are porphyritic rhyodacites containing phenocrysts of dominantly plagioclase, K-feldspar, and quartz within a crystalline groundmass (Fig. 2c and d; Table 1). All samples contain variable quantities of secondary minerals (cristobalite, hematite, smectite, and kaolinite; Table 1).
The tensile strength of volcanic rocks is an important parameter for understanding and modelling a wide range of volcanic processes, and in the development of strategies designed to optimise energy production in volcanic geothermal reservoirs. However, despite the near-ubiquity of hydrothermal alteration at volcanic and geothermal systems, values of tensile strength for hydrothermally altered volcanic rocks are sparse. Here, we present an experimental study in which we measured the tensile strength of variably altered volcanic rocks. The alteration of these rocks, quantified as the weight percentage of secondary (alteration) minerals, varied from 6 to 62.8 wt%. Our data show that tensile strength decreases as a function of porosity, in agreement with previous studies, and as a function of alteration. We fit existing theoretical constitutive models to our data so that tensile strength can be estimated for a given porosity, and we provide a transformation of these models such that they are a function of alteration. However, because porosity and alteration influence each other, it is challenging to untangle their individual contributions to the measured reduction in tensile strength. Our new data and previously published data suggest that porosity exerts a first-order role on the tensile strength of volcanic rocks. Based on our data and observations, we also suggest that (1) alteration likely decreases tensile strength if associated with mineral dissolution, weak secondary minerals (such as clays), and an increase in microstructural heterogeneity and (2) alteration likely increases tensile strength if associated with pore- and crack-filling mineral precipitation. Therefore, we conclude that both alteration intensity and alteration type likely influence tensile strength. To highlight the implications of our findings, we provide discrete element method modelling which shows that, following the pressurisation of a dyke, the damage within weak hydrothermally altered host-rock is greater and more widespread than for strong hydrothermally altered host-rock. Because the rocks in volcanic and geothermal settings are likely to be altered, our results suggest that future modelling should consider the tensile strength of hydrothermally altered volcanic rocks.
The thermal properties of hydrothermally altered andesites from La Soufrière de Guadeloupe (Eastern Caribbean)
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The alteration of the blocks from Merapi volcano—the percentage of secondary minerals in the block—ranges from 7.5 wt% up to 62 wt% (Table 3). The blocks from Chaos Crags, described in Ryan et al. (2020) and Heap et al. (2021b), are porphyritic rhyodacites containing phenocrysts of dominantly plagioclase, K-feldspar, and quartz within a crystallised groundmass. Secondary minerals include cristobalite, hematite, smectite, and kaolinite (Heap et al., 2021b).
The heat flux of an active volcano provides crucial information on volcanic unrest. The hydrothermal activity often responsible for volcanic unrest can be accompanied by an increase in the extent and intensity of hydrothermal alteration, which could influence the thermal properties of the volcanic edifice. Therefore, an understanding of the influence of alteration on the thermal properties of rocks is required to better interpret volcano heat flux data. We provide laboratory measurements of thermal conductivity, thermal diffusivity, and specific heat capacity for variably altered (intermediate to advanced argillic alteration) andesites from La Soufrière de Guadeloupe (Eastern Caribbean). We complement these data with previously published data for altered basaltic-andesites from Merapi (Indonesia) and new data for altered rhyodacites from Chaos Crags (USA). Our data show that thermal conductivity and thermal diffusivity decrease as a function of increasing porosity, whereas the specific heat capacity does not change systematically. Thermal conductivity decreases as a function of alteration (the percentage of secondary minerals) for the rocks from La Soufrière and Merapi (from ~1.6 to ~0.6 W·m⁻¹·K⁻¹ as alteration increases from ~1.5 to >75 wt%), but increases for the rocks from Chaos Crags (from ~1.1 to ~1.5 W·m⁻¹·K⁻¹ as alteration increases from ~6 to ~15 wt%). Although the thermal diffusivity of the rocks from Chaos Crags increases from ~0.65 to ~0.75–0.95 mm²·s⁻¹ as alteration increases from ~6 to ~15 wt%, the thermal diffusivity of the rocks from La Soufrière and Merapi does not appear to be greatly influenced by alteration. The specific heat capacity is not significantly affected by alteration, although there is a slight trend of increasing specific heat capacity with alteration for the rocks from La Soufrière. We conclude that the decrease in thermal conductivity as a function of alteration in the rocks from La Soufrière and Merapi is the result of the low conductivity of the secondary mineral assemblage, and that a combination of the high thermal conductivity of cristobalite and the reduction in porosity as a result of the void-filling mineral precipitation can explain the increase in thermal conductivity in the rocks from Chaos Crags. Calculations show that an increase in alteration of a dome or edifice can result in decreases and increases in heat flow density, depending on the type of alteration. Therefore, alteration-induced changes in the thermal properties of dome or edifice rocks should be considered when interpreting volcano heat flux data. We conclude that it is important not only to monitor the extent and evolution of alteration at active volcanoes, but also the spatial distribution of alteration type.
Mechanical and topographic factors influencing lava dome growth and collapse
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A good example of a complex centre of multiple domes/lobes is Chaos Crags, a centre consisting of six rhyodacitic domes (named Domes A to F in chronological order of emplacement). These domes represent the youngest eruption in the Eagle Peak sequence (Clynne et al., 2008) and are part of the Lassen volcanic center in California, USA (Clynne and Muffler, 2017; Ryan et al., 2020). The majority of Dome C collapsed approximately 350 years ago (Clynne and Muffler, 2017), leaving a semi-spherical collapse scar and a large avalanche deposit called Chaos Jumbles that extends NW of the remnants of Dome C.
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During the numerical experiments, the elements within the sample can move freely in the horizontal direction, but are fixed in the vertical direction due to the position on the loading platens (as is the case for tensile experiments in the laboratory, see below). Cylindrical samples, 40 mm in diameter and 20 mm in length, were prepared from blocks of material have been the subject of recent laboratory studies: rhyodacite from Chaos Crags (Lassen Volcanic Center, USA; Ryan et al., 2020; Heap et al., 2021), trachyandesite from the Chaîne des Puys near Volvic (France; Heap and Violay, 2021), andesites from Volcán de Colima (Trans-Mexican Volcanic Belt, Mexico; Heap et al., 2015b; Farquharson et al., 2016, 2017) and Kumamoto (Japan; Farquharson et al., 2016), basaltic-andesites from Merapi volcano (Sunda arc, Indonesia; Heap et al., 2019b), basalt from Mt. Etna (Italy; Zhu et al., 2016), and tuff from Campi Flegrei and Mt. Epomeo (both Italy; Heap et al., 2014b, Marmoni et al., 2017; Heap et al., 2018). Samples were prepared to a diameter of 40 mm, rather than 50 mm (the diameter used for the numerical experiments), due to the small size of some of the blocks of material.
The tensile strength of volcanic rock exerts control over several key volcanic processes, including fragmentation and magma chamber rupture. Despite its importance, there is a paucity of laboratory data for the tensile strength of volcanic rocks, leading to an incomplete understanding of the influence of microstructural parameters, such as pore size and shape (factors that vary widely for volcanic rocks), on their tensile strength. To circumvent problems associated with the variability of natural samples, we provide here a systematic study in which we use elastic damage mechanics code “Rock Failure Process Analysis” to perform numerical experiments to better understand the influence of porosity, pore diameter, pore aspect ratio, and pore orientation on the tensile strength of volcanic rocks. We find that porosity and pore diameter exert a first-order control on the tensile strength of volcanic rocks, and that pore aspect ratio and orientation also influence tensile strength. Tensile strength is reduced by up to a factor of two as porosity is increased from 0.05 to 0.35 or as pore diameter is increased from 1 to 2 mm. Small, but systematic, reductions in tensile strength are observed as the angle between the loading direction and the major axis of an elliptical pore is increased from 0 to 90°. The influence of pore aspect ratio (the ratio of the minor to major axis of an ellipse) depends on the pore angle: when the pore angle is 0°, a decrease in pore aspect ratio, from 1 (a circle) to 0.2, increases the tensile strength, whereas the same decrease in pore aspect ratio does not substantially change the tensile strength when the pore angle is 90°. These latter numerical experiments show that the tensile strength of volcanic rocks can be anisotropic. Our numerical data are in broad agreement with new and compiled experimental data for the tensile strength of volcanic rocks. One of the goals of this contribution is to provide better constrained constitutive models for the tensile strength of volcanic rocks for use in volcano modelling. To this end, we present a series of theoretical and semi-empirical constitutive models that can be used to determine the tensile strength of volcanic rocks, and highlight how tensile strength estimations can influence predictions of magma overpressures and assessments of the volume and radius of a magma chamber.
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Imaging strain localisation in porous andesite using digital volume correlation
2020, Journal of Volcanology and Geothermal Research
Citation Excerpt :
An impressive example of a lava dome fracture is the 200 m-long and 40 m-wide fracture that formed within the dome at Merapi volcano (Indonesia) following an explosion in 2013 (Walter et al., 2015). Lava spines are extruded along gouge rich conduit-margin faults (e.g., Iverson et al., 2006; Cashman et al., 2008; Kennedy and Russell, 2012; Hornby et al., 2015; Lamb et al., 2015; Ryan et al., 2018, 2020). The spines extruded at Mt. St Helens (USA) from 2004 to 2008, for example, were mantled by a 1–3 m-thick layer of cataclasites, breccias, and gouge (e.g., Cashman et al., 2008).
Strain localisation structures, such as shear fractures and compaction bands, are of importance due to their influence on permeability and therefore outgassing, a factor thought to influence eruptive style. In this study, we aim to develop a better understanding of strain localisation in porous volcanic rocks using X-ray tomographic images of samples of porous andesite (porosity = 0.26) acquired before and after deformation in the brittle and ductile regimes. These 3D images have been first analysed to provide 3D images of the porosity structure within the undeformed andesite, which consists of a large, well-connected porosity backbone alongside many smaller pores that are either isolated or connected to the porosity backbone by thin microstructural elements (e.g., microcracks). Following deformation, porosity profiles of the samples show localised dilation (porosity increase) and compaction (porosity reduction) within the samples deformed in the brittle and ductile regimes, respectively. Digital volume correlation (DVC) of the images before and after triaxial deformation was used to quantify the tensor strain fields, and the incremental divergence (volumetric strain) and curl (used as an indicator of shear strain) of the displacement fields were calculated from the DVC. These fields show that strain localisation in the sample deformed in the brittle regime manifested as a ~ 1 mm-wide, dilatational shear fracture oriented at an angle of 40–45° to the maximum principal stress. Pre- and post-deformation permeability measurements show that permeability of the sample deformed in the brittle regime increased from 3.9 × 10⁻¹² to 4.9 × 10⁻¹² m², which is presumed to be related to the shear fracture. For the sample deformed in the ductile regime, strain localised into ~1 mm-thick, undulating compaction bands orientated sub-perpendicular to the maximum principal stress with little evidence of shear. Taken together, our data suggest that these bands formed during large stress drops seen in the mechanical data, within high-porosity zones within the sample, and within the large, well-connected porosity backbone. Pre- and post-deformation permeability measurements indicate that inelastic compaction decreased the permeability of the sample by a factor of ~3. The data of this study assist in the understanding of strain localisation in porous volcanic rocks, its influence on permeability (and therefore volcanic outgassing), and highlight an important role for DVC in studying strain localisation in volcanic materials.

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Cyclic shear zone cataclasis and sintering during lava dome extrusion: Insights from Chaos Crags, Lassen Volcanic Center (USA)

Highlights

Abstract

Introduction

Section snippets

Chaos Crags

Methods

Geochemistry and mineralogy

Discussion

Implications beyond Chaos Crags

Conclusion

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgements

Data availability

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Phys. Chem. Earth

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

J. Volcanol. Geotherm. Res.

J. Volcanol. Geotherm. Res.

J. Volcanol. Geotherm. Res.

Earth Planet. Sci. Lett.

J. Volcanol. Geotherm. Res.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

J. Volcanol. Geotherm. Res.

Geochim. Cosmochim. Acta

Practical applications of hot-isostatic pressing diagrams: four case studies

Metall. Trans. A.

From dome to dust: shallow crystallization and fragmentation of conduit magma during the 2004–2006 dome extrusion of Mount St. Helens, Washington

Geologic map of the Lassen Peak, Chaos Crags, and Upper Hat Creek area, California

Stratigraphic, lithologic, and major element geochemical constraints on magmatic evolution at Lassen Volcanic Center, California

J. Geophys. Res.

Geologic map of Lassen Volcanic National Park and vicinity

Geological field-trip guide to the Lassen segment of the Cascades Arc, Northern California

Radiocarbon dates from volcanic deposits of the Chaos Crags and Cinder Cone eruptive sequences and other deposits, Lassen Volcanic National Park and vicinity, California

Major and EDXRF trace element chemical analyses of volcanic rocks from Lassen Volcanic National Park and vicinity, California

Natural and experimental evidence of melt lubrication of faults during earthquakes

Science

The 2004–2008 dome-building eruption at Mount St. Helens, Washington: epilogue

Bull. Volcanol.

A volcanic degassing event at the explosive-effusive transition

Geophys. Res. Lett.

Cataclasis and the generation of Fault Gouge

GSA Bull.

Rheologic properties and kinematics of emplacement of the Chaos Jumbles rockfall avalanche, Lassen Volcanic National Park, California

J. Geophys. Res.

Inelastic compaction and permeability evolution in volcanic rock

Solid Earth

Pore fluid pressure development in compacting fault gouge in theory, experiments, and nature

J. Geophys. Res. Solid Earth

Nature and Evolution of Conduit Faults in the 2004–2008 Mount St. Helens Lava Dome Eruption

Pathways for degassing during the lava dome eruption of Mount St. Helens 2004–2008

Geology

A new model for volcanic earthquake at Unzen Volcano: melt rupture model

Geophys. Res. Lett.

Microstructural controls on the physical and mechanical properties of edifice-forming andesites at Volcán de Colima, Mexico

J. Geophys. Res. Solid Earth

Hydrothermal alteration of andesitic lava domes can lead to explosive volcanic behaviour

Nat. Commun.

Dating Chaos Jumbles, an avalanche-deposit in Lassen Volcanic National Park

Am. J. Sci.

Spine growth and seismogenic faulting at Mt. Unzen, Japan

J. Geophys. Res. Solid Earth

The nature and formation of cristobalite at the Soufrière Hills volcano, Montserrat: implications for the petrology and stability of silicic lava domes