Landform Geography Lecture 5

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Landform GeographyLecture 5
Mass Wasting Events Groundwater
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Mass Wasting

• Large volumes of sediment moving down hill slopes
  under force of gravity
• Types

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Solifluction

• Form of soil creep in tundra landscapes
• Surface of permafrost melts soil sags down
  slope in uneven lobes

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Earth Flow

• Slow-to-rapid movement of wet soil other loose
  sediment over a broad surface
• One of 3 types of Flow mass movement of wet
  sediment

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Mudflow

• Fine textured sediments that move very quickly
  down slope occur after heavy rainfall
• Lahar Indonesian word for volcanic mudflow

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Debris Flow

• Mud, boulders, trees, etc. flowing down slope
  after heavy rainfall very dangerous

La Conchita, CA Debris Flow
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Slump

• Slide where rock sediment rotates moves down
  slope along plane concave to surface
• Happens on slopes w/ soft deposits rich in clay
  and shale

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Debris Slide

• Type of Landslide mass of rock, regolith soil
  that flows downhill
• Slope failure along a plane roughly parallel to
  the slope

Madison Slide, Montana
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Soil Creep

• Slowest mass wasting process
• Force of gravity slowly pulls soil particles down
  hill features of hill shift down hill, as well

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Rockfall

• Process in which rocks break free from cliff
  faces rapidly tumble into valley below

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Avalanche

• Large mass of snow or rock that suddenly slides
  down a mountainside

Weathering and Mass Movements
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Groundwater and Karst Landscapes

• Movement Storage of groundwater
• High Plains aquifer
• Subsidence
• Groundwater contamination
• Karst Landforms Landscapes
• Caves Caverns
• Karst topography

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Movement Storage of Groundwater

• Precipitation sinks into soils soil-water belt
• In dry soil, water is held tight by sediment
  grains as hygroscopic water unavailable for
  plants
• When pore spaces within soil full of water, soil
  at Field Capacity additional water flows down
  into unsaturated zone
• Water collects above an impermeable aquiclude to
  form saturated zone
• Large saturated zone is aquifer

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Fate of Precipitation on Soil
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Soil-Water Conditions
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Saturated Zones Aquicludes
Hydrologic Cycle and Groundwater
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High Plains (Ogallala) Aquifer

• Underlies much of Great Plains from TX to SD
• Water deposited in Ice Ages 1.6 M-10K yrs ago

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High Plains (Ogallala) Aquifer

• Heavy usage, esp. center-pivot irrigation
• Drawdown significant in parts of aquifer

Center-Pivot Irrigation
Drawdown
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Artesian Wells and Springs

• Natural pressure brings water to surface in
  artesian well

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Patterns of Groundwater Depletion

• Cone of Depression cone-shaped depression in
  water table that occurs around a well

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Subsidence

• Settling or sinking of a surface due to removal
  of water or sediment from below
• Worst around large cities such as Venice, Italy
  and agricultural regions such as the San Joaquin
  Valley of California

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Groundwater Contamination

• Dumped chemicals can be carried by moving
  groundwater to sources of drinking water
• Recent federal rules have reduced uncontrolled
  dumping and contamination