There are several collapse scarps on the mountain, especially around its central sector. A sector collapse took place on the southwestern flank and formed a landslide deposit as well as a horseshoe-shaped valley that was later filled by glaciers. Also on the southern side, mud-water flow deposits have been found in the Capiza River valley and appear to relate to Coropuna; at least eight such debris flows have been identified. Lahars (mudflows) have reached the Colca River valley. Lahars are dangerous phenomena owing to their high speed and density, causing large scale destruction and fatalities.