Rock glacier is a lobate to tongue-shaped mass of rock, ice, snow, mud and water, moving down a valley or a slope, with little ice visible on the surface. They can be found in high mountains above the timberline and in subpolar areas.
The origin of rock glaciers is still not fully recognised. One group of scientists states that they are strictly the result of periglacial processes (only related to permafrost), the other group argues that rock glaciers may also evolve from debris-covered glaciers.
Rock glaciers are a source of fresh water supply to the agglomerations of Santiago, Chile (5.3 million inhabitants), and Mendoza, Argentina (1.1 million inhabitants).