GEOGRAPHY 121 FINAL EXAM

GEOGRAPHY 121 FINAL EXAM - GEOGRAPHY 121 FINAL EXAM Chapter...

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GEOGRAPHY 121 FINAL EXAM Chapter 16: Underground Water and Karst Landforms - Earth’s fresh water resources are very limited o 70% is stored as glacier ice in polar regions o 30% is underground - Underground Water System in Humid Regions (Figure 16.2) o Primary Inputs: precipitation and snowmelt infiltrating the ground o Major Output (outflow) occurs through dug wells/natural springs o Percolation: process by which water drains downward by gravity beyond the zone of aeration to lower levels o Subsurface Water System has Three Layers Zone of Aeration Intermediate Zone Zone of Saturation: Water occupies all of the void spaces in this zone - groundwater Top of zone of saturation is the water table Water table dept is dependant on changes in infiltration and outflow, falling during dry seasons and rising during wet seasons Water table is the surface of the zone of saturation through which water flows towards a nearby river - Aquifer : a natural underground storage medium for groundwater. o When impermeable rock exists below an aquifer a perched water table can form because the downward percolating soil water was prevented from reaching the zone of saturation o A sequence of porous and permeable layers of sediments of rock that act as a storage medium and transmitter of water Sandstones, limestone, loose coarse sediments o - Pumping of water from wells may cause the development of cones of depression – adjacent cones of depression can lower the regional water table causing shallow wells to become dry o Wells are artificial openings dug or dilled below the water table to extract water - Principal Role of subsurface water in landform development is to encourage mass movement by adding weight and reducing strength of soil/sediments - Limestone is the most common soluble rock – wherever water can act on a rock type that’s soluble in water, a distinctive landscape will develop - Karst Landforms – landforms developed dominantly by solution, named after the Karst Plateau along Croatia o Necessary Circumstances for development of Karst Landscape Warm humid climate with ample precipitation Presence of carbon dioxide from vegetation – warmer climates Active movement of subsurface water - Sinkholes: roughly circular surface depressions developed by concentrated solution; prominent feature of karst landscapes - Figure 6.10 – distribution of limestone in the US
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o High concentrations in Florida, Texas, just west of the Mississippi - Groundwater flowing along joints and bedding planes below the surface can dissolve limestone sometimes creating a system of connected passageways within soluble bedrock - if the water table falls and these passageways are above the zone of saturation this is called a cave o Caverns develop along zones of weakness and groundwater flow widens (limestone) fractures to develop a cave system - Karst Topography o Florida’s central lake region is a good place to study karst topography
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