A form of landslide where a water-saturated upper soil layer and the vegetation growing on it slides over an underlying less permeable subsoil creating a relatively shallow, narrow slide scar, usually two to three feet deep and 15 to 30 feet wide.
The sudden downslope movement of rock and soil on a steep slope.
Rapidly moving, dry flows of disaggregated rock debris, sand, and silt. Volcanic debris avalanches commonly form by some type of structural collapse of the volcano, usually the steep front of the cooled lava dome, or other parts of the upper edifice. A large portion of the volcano may become unstable, break away from the volcanic massif, and become an avalanche. A debris avalanche may be triggered by an eruption or earthquake. Debris avalanches move at velocities ranging from a few tens of meters per second to more than 100 meters per second and behave like complex granular flows or slide flows. Commonly they are quite voluminous (greater than 10 cubic kilometers) and may run out considerable distances (up to 85 kilometers) from their source. The resulting debris-avalanche deposit usually exhibits hummocky surface morphology.
a sudden and rapid movement of rock due to gravity usually resulting from a collapse of the side of a volcano
a very rapidly moving mass of rock, sediment, air, and water
A rapid mass movement that may include volcanic rock, water, snow, glacier ice, trees and other pyroclastic material.
the very rapid and usually sudden sliding and flowage of an unsorted mixture of soil and weathered (altered) rock
a downward slide of loose, earthen material (soil, mud, and small rocks) that begins suddenly and travels at great speeds - similar to a snow avalanche. It builds into a fearsome mass of mud, trees, and rocks that can cause much damage.
Dense, incoherent mixture of water, rock, and soil that flows downslope at speeds of 40 to 200 kilometers/hour (25 to 125 miles/hour).
A rapid and unusually sudden sliding or flowage of unsorted masses of rock and other material. As applied to the major avalanche involved in the eruption of Mount St. Helens, a rapid mass movement that included fragmented cold and hot volcanic rock, water, snow, glacier ice, trees, and some hot pyroclastic material. Most of the May 18, 1980 deposits in the upper valley of the North Fork Toutle River and in the vicinity of Spirit Lake are from the debris avalanche.
An avalanche in which the falling debris consists of rock fragments and dust.
A debris avalanche is a sudden rock/soil/debris slide and flows with great speed from a volcano.
Geologic deposit and event related to a Landslide, but containing abundant snow and/or ice. As the debris tumbles downslope, the snow and ice break apart giving the slide more mobility and speed.
Catastrophic landsliding of gravitationally unstable volcano flanks resulting in a widely dispersed deposit at the foot of the edifice, typically characterized by a hummocky surface.
A sudden catastrophic collapse of volcanic material from an unstable side of a volcano.
A fast downhill mass movement of soil and rock.