![Elements for reconstructing the amount of collapsed rockslide material in the Sabche cirque and the initial rockslide failure surface. Maps of the base (a) and top (b) of brecciated rock-avalanche deposits, including interpolation constraints, and current residual thickness of breccia deposits (c). d, Sabche rockslide scar identification from transverse curvature (m−1) calculated from high-resolution (2-m pixel) topography. The recent scar surface (3 and 4) is characterized by step-like dihedrals that delineate planar surfaces with low curvature along the stratification/foliation planes and irregular surfaces that follow a set of fractures at 90 °. On the contrary, except for the scar (1 and 2), the topography shows the first signs of erosion and gullies organization towards a converging network. Credit: Nature (2023). DOI: 10.1038/s41586-023-06040-5 Evidence found of giant rock slides in the Himalayas during the Middle Ages](https://scx1.b-cdn.net/csz/news/800a/2023/evidence-found-of-gian.jpg)
Elements for reconstructing the amount of collapsed rockslide material in the Sabche cirque and the initial rockslide failure surface. Maps of the base (a) and top (b) of brecciated rock-avalanche deposits, including interpolation constraints, and current residual thickness of breccia deposits (c). d, Sabche rockslide scar identification from the transverse curvature (m-1) computed from high-resolution (2-m pixel) topography. The recent scar surface (3 and 4) is characterized by step-like dihedrals that delineate planar surfaces with low curvature along the stratification/foliation planes and irregular surfaces that follow a set of fractures at 90 °. On the contrary, except for the scar (1 and 2), the topography shows the first signs of erosion and gullies organization towards a converging network. Credit: NATURE (2023). DOI: 10.1038/s41586-023-06040-5
A group of geologists affiliated with several French institutions, working with a colleague in Nepal, found evidence of a large rockslide that occurred in a part of the Himalayas during the medieval period. In their study, the journal reported NATUREthe team analyzed parts of the Sabche Cirque, a Himalayan basin.
Previous research has shown that some mountains are too high to fall victim to the kinds of erosion that erode shorter mountains—they’re so high that temperatures near the summit are often below freezing, for example, preventing cracking accompanying freezing/cold. cycles in low altitude mountains. Such mountains are also too high and steep to accommodate glaciers. Instead, the researchers of this new effort argued, they collapsed like a rock slide.
In Nepal, there is a mountain range called Annapurna—it has some of the highest peaks in the world. Between the peaks are valleys, plains or basins, most of which are similar to others like them. However, this is not the case in Sabche Cirque—instead of fertile soil, it is mostly covered with rocks. Suspecting that the rocks might be the remains of a century-old slide, the team took a closer look.
The team found that the rocks are breccia, smaller rocks embedded in larger rocks. Excavation revealed that the size of the embedded stones increased the deeper they went. Next they opened some rocks and carbon-dated plant material they found embedded inside. They all date back to approximately 1200 CE. Next, they found that one of the peaks next to the Sabche Cirque experienced shearing on one of its faces, suggesting that material fell from it into the valley below.
Evidence strongly suggests that a massive rock slide occurred around 1200 CE, filling the valley below with debris up to a kilometer deep. Researchers suggest that before the rock slide, the peak where it happened was probably more than 8,000 meters high, which means it lost about half a kilometer in height.
More information:
Jérôme Lavé et al, Medieval demise of a giant Himalayan summit caused by a mega-landslide, NATURE (2023). DOI: 10.1038/s41586-023-06040-5
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Citation: Evidence found of giant rock slide in the Himalayas during the Middle Ages (2023, July 6) retrieved 7 July 2023 from https://phys.org/news/2023-07-evidence-giant-himalayas- medieval.html
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