sturzstrom

thumb|The Mount St. Helens landslide was a sturzstrom. The slide took place on the north face, and created the valley-like gap seen here.

A Sturzstrom (from the German Sturz (fall) and Strom (stream, flow)) or rock avalanche is a large landslide, consisting of soil and rock. It travels a great horizontal distance compared to its initial vertical drop (as much as 20 or 30 times). Sturzstroms have similarities to the flow of glaciers, mudflows, and lava flows. They flow across land fairly easily, and their mobility increases when volume increases. They have been found on other bodies in the Solar System, including the Moon, Mars, Venus, Io, Callisto, Iapetus, and Phobos.