Notes for Test 4

Notes for Test 4 - Notes for Test 4 CHAPTER 16 MASS WASTING...

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Notes for Test 4 * CHAPTER 16 – MASS WASTING o Includes all processes by which rock/soil move downhill under influence of gravity. o A consequence of weathering, & is important part of general erosion, especially in mountainous areas o Human interference can cause severe effects. In the USA, excavation for buildings/homes causes more soil to be transported than by all natural processes * What factors control rate and amount of mass wasting? o 1- nature of rock/soil HUnconsolidated – loose not cemented material HConsolidated – compacted and bound together material o 2- steepness and stability if slope o 3- amount of water in the materials (SEE TABLE 16.4) * Unconsolidated material o Angle of repose is critical o Is the maximum angle from the horizontal that material will lie without cascading down. o Depends on the shape/size of material (grains) and the degree of wetness. o FIG 16.3 * Steepness of slope for rocks o Depends on type of rock and degree of weathering o (Softer) Shales and volcanic ash weather to gentle inclines o Hard sandstones, limestones, granite weather to (almost) vertical cliffs * What triggers mass movements? o If type of material, moisture and steepness of slope are “right”, heavy rainfall, and earthquakes can be the trigger. o FIG 16.17 o Not responsible for “rock mass movements” (P. 388-394) o For unconsolidated material – look to (soil) creep – slow (~1- 10mm/yr) downhill movement of loose material (FIG 16.21) o Other forms faster, slump, debrissilde etc. – not responsible for details * Natural landslides o Case in Western Wyoming (FIG 16.27) o Can cause widespread devastation (FIG 16-24) * Mass wasting
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o Common in all plate tectonic settings HMost obvious near convergent plate boundaries, where (high) mountains are formed. HAlso occurs on ocean beds. o Man’s activities contribute to erosion and mass wasting – especially cutting away vegetation and building strip malls. * CHAPTER 17 - GROUNDWATER o Following rainfall, part of the water flows off at surface into streams (CHAPTER 18) o Some of the water percolates into the ground – and forms a reservoir – groundwater. * Water at earth’s surface o 96% of the water is salty (in the oceans). o Of the 4% fresh water, reservoirs are in order of importance: HGlaciers and polar ice HGroundwater HLakes and rivers HAtmosphere and biosphere HFIG 17.1 * Hydrologic cycle o There is a balance between (level) of water in the oceans, evaporation of this water, and precipitation by rain/snowfall. o Called the hydrologic cycle * P.B. Shelley (”Clouds” ~1820) o “I am the daughter of earth and water and the nursling of the sky I pass through the pores of oceans and shores I change, but cannot die” * Sea levels rising and falling: o During glacial periods, water drawn out of oceans and dumped as snow on land – sea level falls. o
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Notes for Test 4 - Notes for Test 4 CHAPTER 16 MASS WASTING...

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