Earthflow
Encyclopedia
An earthflow is a downslope viscous flow of fine grained materials that have been saturated with water, and moves under the pull of gravity. They are an intermediate type of mass wasting
that is between downhill creep and mudflow
. The types of materials that are susceptible to earthflows are clay
, fine sand
and silt
, and fine-grained pyroclastic material.
When the ground materials become saturated with enough water they will start flowing. Its speed can range from being barely noticeable to rapid movement. The velocity of the flow is dictated by water content: the higher the water content is, the higher the velocity will be. Because of the dependency on water content for the velocity of the flow, it can take minutes or years for the materials to move down the slope.
An earthflow may affect as few as several square meters or up to several hectares.
Mass wasting
Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place...
that is between downhill creep and mudflow
Mudflow
A mudslide is the most rapid and fluid type of downhill mass wasting. It is a rapid movement of a large mass of mud formed from loose soil and water. Similar terms are mudflow, mud stream, debris flow A mudslide is the most rapid (up to 80 km/h, or 50 mph) and fluid type of downhill mass...
. The types of materials that are susceptible to earthflows are clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
, fine sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
and silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
, and fine-grained pyroclastic material.
When the ground materials become saturated with enough water they will start flowing. Its speed can range from being barely noticeable to rapid movement. The velocity of the flow is dictated by water content: the higher the water content is, the higher the velocity will be. Because of the dependency on water content for the velocity of the flow, it can take minutes or years for the materials to move down the slope.
An earthflow may affect as few as several square meters or up to several hectares.
External links
- Slumgullion earthflow, USGS Bulletin 2130, a National Natural LandmarkNational Natural LandmarkThe National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...
in ColoradoColoradoColorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, USA.