Geology study guide exam 3

Geology study guide exam 3 - Mass Wasting Mass wasting: the...

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Mass Wasting Mass wasting : the down slope (hill) movement of rock, soil, or sediment under the influence of gravity. Mass wasting events occur in different ways and at different rates, depending on the types of materials involved (such as rock, soil or earth, mud, debris ) and the motion involved ( fall, slide, flow ). Factors that effect mass wasting include: Nature of the materials (unconsolidated sediment-soil or consolidated rock) Steepness of slope Water: groundwater can create pressures that destabilize a slope, ALSO, flowing water saturates the soil, thus weakening the slope Vegetation Presence and orientation of planes of weakness (bedding, joints, metamorphic foliations (i.e. potential slide surfaces) heights Climate (in addition to precipitation, freeze-thaw cycles are important) Some natural processes that over-steepen slopes include: Stream erosion Wave erosion Tectonic uplift Volcanic activity Landslide is the general term referring to all slides, flows (even falls) that occur at a moderately fast rate. They cost the United States nearly 6 billion dollars per year. Humans by can cause landslides: Deforestation Blasting and earthwork Vibrations from traffic Any man-made changes in water flow Fall (Fastest)
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EXAMPLES: prehistoric Blackhawk Slide, Frank (Alberta) slide in 1902 Air travels beneath the slide, allowing in to spread across massive distances Often leaves minor vegetation relatively undisturbed Debris Flow (Fast) EXAMPLES: Mount St. Helens, Glenwood Springs (Colorado), 1999 in Venezuela, and the 1992 Mount Mayuyama slide that created a tsunami Slope material becomes saturated and develops into an debris/mud flow Picks up rocks, soil, mud, trees, cars, houses, etc. Often mistaken for a flash floods because of the rapid and unannounced occurance Most dangerous debris flows accompany volcanoes Avalanche (Fast) EXAMPLE: Hauscaran Mountain avalanche in Yungay, Peru Ice and snow picks up debris, rapidly charging downhill Slumps: (Slow-Fast) EXAMPLE: The 1994 La Conchita Slide began as a slump Material moves as coherent mass along curved surfaces. This motion results in a slightly backward rotation of blocks. Note that the ground surfaces on the intermediate blocks dip slightly toward the master sole of the slump. The distal end (toe) of the slump moves along a less steep surface. Often the toe of slumps moves more as a flow than as a slide. Earth Flow (Slower) EXAMPLES: The 1994 La Conchita Slide (moderately fast), Slumgullion Earthflow (slow, long-lasting), Down-slope, viscous, flows of saturated materials Carried along by flow from within More water = higher velocity
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Begin when the pore pressures in a fine-grained mass increase until enough of the weight of the material is supported by pore water to significantly decrease the internal shearing strength of the material. This thereby creates a bulging lobe, which advances with a slow,
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This note was uploaded on 03/21/2012 for the course GEOLOGY (G 1000 taught by Professor Leroyodom during the Fall '10 term at FSU.

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Geology study guide exam 3 - Mass Wasting Mass wasting: the...

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