Mass Movement Essay

11290 WordsMay 20, 201446 Pages
Mass movement is the movement of surface material caused by gravity. Landslides and rockfalls are examples of very sudden movements of this type. Of course geological agents such as water, wind and ice all work with gravity to cause a leveling of land. | A block diagram of an earth flow where movement is a combination of slip and flow. | Water aids in the downslope movement of surface material in several ways. Water adds weight to the soil; it fills pore spaces of slope material and it exerts pressure which tends to push apart individual grains. This decreases the resistance of the material to movement. Landslide is a general term that is commonly broken down into the more specialized terms such as slump, rockslide, debris slide, mudflow and earthflow. Slump A slump is a downward and outward movement of rock or unconsolidated material moving as a unit or series of units. Large blocks of material move suddenly downward and outward along a curved plane. Rockslide Rockslides are the most catastrophic type of landslide. They involve a sudden rapid slide of bedrock along planes of weakness. Rockslides are very common in the oversteepened canyons and drainages of Idaho, particularly in those areas like the Salmon River Canyon where more than 5,000 feet of elevation may exist between the ridge tops and the canyon bottoms. Debris Slide A debris slide is a small sudden downstope movement of unconsolidated material. This type of slide produces a hummocky surface of low relief. Mudflow A mudflow is a mass of saturated rock particles of all sizes. This type of landslide is caused by a sudden flood of water from a cloudburst in semi-arid country or a sudden thaw. The flood waters carry the soil and rocks from a large slope area and washes them to a gulch or canyon. 'Then the water and debris move down the canyon and spread out on the gentle slopes below.

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