landform geography groundwater and karst landscapes
TRANSCRIPT
![Page 1: Landform Geography Groundwater and Karst Landscapes](https://reader035.vdocuments.mx/reader035/viewer/2022081506/56649cbf5503460f949859e1/html5/thumbnails/1.jpg)
Landform Geography
Groundwater and
Karst Landscapes
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Movement & Storage of Groundwater
• Precipitation sinks into soil’s 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
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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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• Heavy usage, esp. center-pivot irrigation
• Drawdown significant in parts of aquifer
High Plains (Ogallala) 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
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Karst Landforms
• Caves, sinkholes and other soluble rock features
• Form in extensive, thick deposits of limestone
• Limestone 80%+ calcium carbonate – dissolves easily through carbonation
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Caves and Caverns• Caves – underground
voids in rock big enough for people to enter
• Cavern – large cave system
• Form just below water table in limestone – when
water table falls, empty caverns are exposed
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Karst Topography - Sinkholes
• Most common surface feature of karst is sinkhole
• Sinkhole – depression in regions of cavernous limestone – forms from collapse of cave
• Often found with disappearing streams that enter underground channels
• Some sinkholes fill with water, forming ponds
• Sinkholes can be hazards, collapsing under homes or roads
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Sinkhole Landscape