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Mass Wasting. Mass wasting - is the name given to all downslope movements of material due to the influence of gravity. They are an important part of the denudation of the landscape. Soil creep
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Mass wasting- is the name given to all downslope movements of material due to the influence of gravity. They are an important part of the denudation of the landscape. • Soil creep • on just about any moderately steep soil covered slope there may be evidence of extremely slow downslope movement of soil. • this is often evidenced by the tilting of trees, poles, gravestones and fences and broken retaining walls • as particles are exposed to heating and cooling, frost action, rainfall and the action of plants and animals, gravity pulls the particles steadily downhill
Earth Flow – LinearEarth Slump - Circular • - in humid climate regions where there are steep slopes, masses of water soaked soil, and overburden may slide downhill in a few hours • sometimes in very saturated clay rich soils (usually left behind in areas that were formerly glacial lakes), the earthflow can become very fluidized very quickly • the whole slope suddenly behaves like a liquid and flows rapidly downhill - Leda clays(“sensitive” or “quick clays”) are found in Ottawa and Quebec react this way • potentially very dangerous - in St. Jean-Vianney, Quebec in 1971 a Leda clay slide killed 31 people • the movement is associated with slumps. Slumps – are rotated blocks of earth – looks as if sitting on a couch.
curved motion failure plane linear motion failure surface
Mudflow • - a stream of fluid mud that pours down canyons in mountainous regions like a river • - especially significant in desert areas where there is little vegetation to hold the soil and heavy rains sometimes occur • they also happen on the sides of volcanoes from freshly fallen ash and dust (fatal eruption of Nevado del Ruiz, Columbia killed 20 000 in mudflow)
MudFlows Leda Clays is a slump and a MudFlow involves movement like a river.
Landslides & Avalanches • the rapid sliding downslope of large masses of rock with little or no flowage of the materials – in other words no water. • rockslides are rare and occur where there are steep slopes • Sometimes set off by kinetic energy – one rock hits another and two hit two more and so on… • often set off by earthquakes or by excavations or construction - roads, railways, dams, etc. • Skiers can also set off an avalanche • Loud sounds do not set off Landslides and Avalanches • eg., Frank, Alberta slide 1903, The Tragedies in BC in 2003
Rock slides is the movement of rocks down a slope. Landslides are rock, earth and debris flows due to gravity Avalanches are landslides involving snow.
