Catastrophic rock avalanche 3600 years BP from El Capitan, Yosemite Valley, California
Catastrophic rock avalanche 3600 years BP from El Capitan, Yosemite Valley, California
复制标题
距今 3600 年前，加利福尼亚州约塞米蒂山谷 El Capitan 发生灾难性岩崩
DOI：
--
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
R. Uhrhammer
中科院分区：
文献类型：
--
作者：
G. Stock;R. Uhrhammer
近垂直悬崖上的大岩坡破坏是推动山地景观演变的重要地貌过程，特别是冰川陡峭的悬崖。约塞米蒂河谷埃尔卡皮坦地下一个2.19×10~6 m~3岩石雪崩沉积物的形态和年龄表明，东南面的一大片史前破裂。矿床和悬崖面的地质填图将岩石雪崩源限制在∼山顶附近8.5×10~4 ~2的区域。岩石自由落体∼650 m，最大速度达到100 m S−1，撞击距骨斜坡并蔓延至谷底，从悬崖底部延伸670 m。矿床中巨石的宇宙成因铍-10暴露年龄平均为3.6±0.2 ka。∼13 KYR在冰川消融和破裂之间的时间滞后表明，岩石雪崩并不是冰川支撑的直接结果。岩石崩塌的∼3·6 ka年龄与估计的欧文斯谷断裂和/或白山断裂在3·3~3·8 ka之间的晚全新世破裂是一致的。年代的重合，再加上最近(公元1872年)欧文斯山谷断裂在约塞米蒂山谷引发了许多大岩崩，表明一场以内华达山脉东南部为中心的大地震(≥M7.0)可能触发了岩崩。如果正确，约塞米蒂山谷岩崩带来的极端危险仍然存在，并取决于当地地震复发的间隔时间。2010年由John Wiley&Sons，Ltd.出版。
Large rock slope failures from near‐vertical cliffs are an important geomorphic process driving the evolution of mountainous landscapes, particularly glacially steepened cliffs. The morphology and age of a 2·19 × 106 m3 rock avalanche deposit beneath El Capitan in Yosemite Valley indicates a massive prehistoric failure of a large expanse of the southeast face. Geologic mapping of the deposit and the cliff face constrains the rock avalanche source to an area near the summit of ∼8·5 × 104 m2. The rock mass free fell ∼650 m, reaching a maximum velocity of 100 m s−1, impacted the talus slope and spread across the valley floor, extending 670 m from the base of the cliff. Cosmogenic beryllium‐10 exposure ages from boulders in the deposit yield a mean age of 3·6 ± 0·2 ka. The ∼13 kyr time lag between deglaciation and failure suggests that the rock avalanche did not occur as a direct result of glacial debuttressing. The ∼3·6 ka age for the rock avalanche does coincide with estimated late Holocene rupture of the Owens Valley fault and/or White Mountain fault between 3·3 and 3·8 ka. The coincidence of ages, combined with the fact that the most recent (AD 1872) Owens Valley fault rupture triggered numerous large rock falls in Yosemite Valley, suggest that a large magnitude earthquake (≥M7.0) centered in the south‐eastern Sierra Nevada may have triggered the rock avalanche. If correct, the extreme hazard posed by rock avalanches in Yosemite Valley remains present and depends on local earthquake recurrence intervals. Published in 2010 by John Wiley & Sons, Ltd.