The highest mountains on the planet are the result of a constant struggle between tectonic forces and erosion. Volcanism and plate collisions push mountains upward, but erosion constantly pulls them downward. However, new research shows that ice, previously thought to be a major factor in erosion, may have less of an effect on the highest mountain peaks than previously thought.
When it comes to the effect of ice on erosion, it is worth noting that on the highest mountain peaks the freeze-thaw cycle stops due to consistently low temperatures. Moreover, most of these peaks are so steep that glaciers have no chance to form.
A new paper published by a group of geologists offers a new perspective on the erosion process of the highest mountain peaks. They argue that mountains not only erode, but also fall, causing powerful landslides that can have catastrophic consequences over a considerable distance from the slope. In support of this fact, the article cites a landslide that covered an area of 20 cubic kilometers in the Annapurna region of Nepal.
The scientists estimated the original volume of material that filled the valley before the landslide, as well as the original extent of the sediment before erosion based on the remaining material. They suggested that the debris was the result of 23 cubic kilometers of rock, making it the largest landslide ever found in the Himalayas.
It is interesting to note that the rock may have spread beyond the valley, where similar deposits can be found several kilometers downstream. These deposits date from about the same period.
By surveying the peaks around the valley, scientists identified a large area below today’s Annapurna IV peak that showed minimal signs of erosion. Instead, they found many flat features that suggest the rock was cut along faults.
By combining the estimated volume of material with the area where these features predominate, the scientists were able to reconstruct the past appearance of Annapurna IV. Their conclusion is that the summit was once higher than 8,000 meters, but had lost about half a kilometer in height due to a landslide.
These new studies provide a better understanding of the processes that occur in the highest mountains on Earth. They also underscore the importance of further research and monitoring of these regions to prevent possible hazards associated with landslides and other natural disasters.