Abstract Catastrophic flank collapses are common on oceanic islands of volcanic origin and often recognizable from the resulting morphology as large U-shaped embayments. However, post-collapse volcanic activity can infill such features, thereby obscuring them. This study takes advantage of a dense network of long sub-horizontal galleries for groundwater extraction in the flank collapse structure of the Orotava Valley (Tenerife, Canary Islands). This impressive landform is located in the overlapping zone of the NE Rift and the Canadas Edifice of this volcanic island. Three debris avalanche deposits (DADs) have been identified inside the waterworks bored into the valley's western sector. The deeper layer, the Lower-DAD (L-DAD) was previously described under the local name of mortalon. This deposit lies unconformably over older volcanic rocks, where a prominent shear-zone is developed, here interpreted as the detachment plane of a massive rockslide. The L-DAD was therefore produced during the large failure event, the Orotava Landslide (OL), which carved the depression. Two younger DADs, much smaller in volume and not previously described, were also identified in the underground strata: the Intermediate- (I-DAD) and Upper-DAD (U-DAD). Both correlate well with the thick breccia deposits cropping out at the base of the marine cliff along the western coast of the valley. The I-DAD and U-DAD are conformably intercalated between the lava flows and other volcanics infilling the depression, and their bases are erosive/depositional features without structural deformation zones below them. Their stratigraphic setting and geometrical reconstruction indicate that both deposits were emplaced after the valley was formed by the OL event, in two successive failures here called Western Orotava Landslides (WOLs). The younger, called WOL-2, was dated at 494 ± 22 ka using the 40Ar/39Ar method. These two subaerial failures affected the upper eastern flank of the Canadas III Edifice, previously destabilized when the OL failure event carved a steep wall at its foot, the western lateral escarpment of the Orotava Valley.

中文翻译：

---

火山海洋岛屿上的多个相关侧翼坍塌：来自奥罗塔瓦河谷水廊（特内里费岛，加那利群岛）中碎屑雪崩沉积物的证据

摘要 灾难性的侧翼坍塌在火山起源的海洋岛屿上很常见，并且通常可以从由此产生的形态中识别为大型 U 形海湾。然而，坍塌后的火山活动可以填充这些特征，从而使它们变得模糊。这项研究利用了一个密集的亚水平长廊网络，在 Orotava 山谷（特内里费岛，加那利群岛）的侧翼坍塌结构中提取地下水。这个令人印象深刻的地貌位于东北裂谷和这个火山岛的加拿大大厦的重叠区。在钻入山谷西部的水厂内发现了三个碎屑雪崩沉积物 (DAD)。更深的一层，Lower-DAD (L-DAD) 之前被描述为 mortalon 的本地名称。该矿床不整合地位于较老的火山岩上，此处发育显着的剪切带，此处解释为大型滑坡的脱离面。因此，L-DAD 是在大型破坏事件 Orotava 滑坡 (OL) 期间产生的，该事件造成了凹陷。在地下地层中也发现了两个体积更小且以前未描述过的年轻 DAD：Intermediate-(I-DAD) 和 Upper-DAD (U-DAD)。两者都与沿着山谷西海岸的海洋悬崖底部出现的厚角砾岩沉积物密切相关。I-DAD 和 U-DAD 共形地嵌入在熔岩流和其他火山岩之间，它们的底部是侵蚀/沉积特征，其下方没有构造变形带。他们的地层设置和几何重建表明，这两个沉积物都是在 OL 事件形成山谷之后就位的，在这里称为西奥罗塔瓦滑坡 (WOL) 的两次连续失败。较年轻的称为 WOL-2，使用 40Ar/39Ar 方法测年为 494 ± 22 ka。这两次地面故障影响了 Canadas III 大厦的上东翼，此前，当 OL 故障事件在其脚下（Orotava 山谷的西部侧崖）刻出一道陡峭的墙壁时，该地区变得不稳定。