A series of rockslides and gravitational slope deformations aligned along the Kali Gandaki across the Nepal Himalaya
A series of rockslides and gravitational slope deformations aligned along the Kali Gandaki across the Nepal Himalaya
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一系列岩石滑坡和重力斜坡变形沿着尼泊尔喜马拉雅山的卡利甘达基山脉排列
DOI：
10.1016/j.geomorph.2021.108098
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发表时间：
2022
期刊：
影响因子：
3.9
通讯作者：
Amatya Shanmukhesh C.
中科院分区：
文献类型：
--
作者：
Chigira Masahiro;Tsou Ching-Ying;Higaki Daisuke;Amatya Shanmukhesh C.
隆起的山脉会因重力变形、山崩、冰川或河流侵蚀而剥蚀。我们调查了山谷斜坡的冰川和河流侵蚀沿着Kali Gandaki（KG）河，最大的河流之一，流经高喜马拉雅山脉向南从西藏到印度和对角削减的片麻岩和板岩面理的罢工。2.5米分辨率的卫星图像和5米数字高程模型（DEM）用于调查。在KG河20公里范围内，我们发现了一系列11个滑坡，每个滑坡的总面积从0.58到1200万平方米不等。叶理一般走向为NW-SE，倾向NE，倾角为30° ~ 50°，因此左岸斜坡为上斜，右岸斜坡为下斜。在下斜斜坡上，岩层发生屈曲，板岩和二云母片麻岩发生逐渐变形，而在更有竞争力的钙质片麻岩中，屈曲变形发展成岩石雪崩。这种岩石雪崩以最大的Dhampu-Chhoya滑坡为代表，该滑坡曾经阻塞KG河并彻底改变了河流形态。二云母片麻岩的回倾斜坡在三个斜坡上倾倒并转化为岩石雪崩。KG河有一个突出的河流转折点，目前海拔1800 m，左岸有坡折，位于转折点下游河床上方200-400 m处。倾倒观察斜坡高于坡折带，这表明倾倒开始之前形成坡折带的河流切割和较低的斜坡不适应年轻的河流切割。相反，在右岸几乎没有发现坡折带，可能是因为跟随河流切割的缓慢移动的DGSD将它们抹去了。
Uplifting mountains are denudated by gravitational deformation, landslides, and glacial or fluvial erosion. We investigated the response of valley slopes to glacial and fluvial erosion along the Kali Gandaki (KG) River, one of the largest rivers that flows through the High Himalaya southward from Tibet to India and diagonally cuts the strikes of gneiss and slate foliations. Satellite images with 2.5 m resolution and 5-m Digital Elevation Models (DEMs) were used for the investigation. Within a 20-km reach of the KG River, we found a series of 11 landslides, which vary from a total area of 0.58 to 12 million m2each. The foliations generally strike NW–SE and dip at 30° to 50° to the NE, so the left bank slopes are anaclinal and the right bank slopes are cataclinal. On the cataclinal slopes, buckling of beds occurs, and gradual deformation proceeds in slate and two-mica gneiss, while in the more competent calc gneiss, buckling deformation develops into a rock avalanche. Such rock avalanches are represented by the largest Dhampu-Chhoya landslide, which once blocked the KG River and drastically changed the river morphology. Anaclinal slopes of two-mica gneiss were toppled and transformed into rock avalanches on three slopes. The KG River has a prominent fluvial knickpoint, which is currently at an elevation of 1800 m, and it has slope breaks on the left bank that are 200–400 m above the riverbed downstream of the knickpoint. Toppling was observed on slopes higher than slope breaks, which suggests that toppling began before the formation of slope breaks by fluvial incision and that the lower slopes did not adapt to the younger fluvial incision. In contrast, slope breaks are scarcely found on the right bank, probably because slow-moving DGSDs, which followed the river incision, erased them.