Monday March 7, 2011. (Groundwater – Environmental Effects and Geologic Work). The Launch Pad Monday, 3/7/11. Name and describe two important functions of groundwater from a geological perspective. . Groundwater is important as an erosional agent, forming sinkholes and cavern systems.
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MondayMarch 7, 2011 (Groundwater – Environmental Effects and Geologic Work)
The Launch Pad Monday, 3/7/11 • Name and describe two important functions of groundwater from a geological perspective. • Groundwater is important as an erosional agent, forming sinkholes and cavern systems. • Groundwater is an equalizer of streamflow, keeping rivers healthy even in time of limited rainfall.
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Complete Worksheet Running Water and Groundwater (Part 2)
Environmental Problems Associated with Groundwater Some localities are concerned with possible contamination of their groundwater supply.
The High Plains extend from the western Dakotas south to Texas. Despite being a land of little rain, this is an important agricultural region. The reason is a vast endowment of groundwater that makes irrigation possible through most of the region.The source of most of this water is the Ogallala formation, the largest aquifer in the U.S.In some agricultural regions, water is pumped from the ground faster than it is replenished.In such instances, water is being treated as a non-renewable resource.
The green area on the map is California’s Joaquin Valley.The marks on the utility pole indicate the level of the surrounding land in preceding years.Between 1925 and 1975, this area subsided almost 9 meters because of the withdrawal of groundwater and the resulting compacting of sediment.
Although the contaminated water has traveled more than 100 metes before reaching well 1, the water moves too rapidly through cavernous limestone to be purified. B. As the discharge from the septic tank percolates through the permeable sandstone, it is purified in a relatively short distance.
Geologic Work of Groundwater Groundwater is often mildly acidic as it contains a weak solution of carbonic acid. This acidic nature will dissolve the calcite in limestone. Caverns are formed by dissolving rock beneath the Earth’s surface. Caverns form in the zone of saturation.
Features Found Within Caverns The deposition of dripstone is not possible until the caverns are above the water table in the unsaturated zone. Dripstone is composed of calcite deposited as dripping water evaporates. Common dripstone features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor.)
Karst Topography Karst topography refers to landscapes that to a large extent have been shaped by the dissolving power of groundwater. These areas have been sculpted by dissolving rock at or near Earth’s surface.
Karst Topography Common features of karst topography include: • sinkholes, which are surface depressions. Sinkholes form by dissolving bedrock and cavern collapse. • caves and caverns present underground. These areas lack good surface drainage.
A Karst Landscape With the passage of time, underground caverns grow larger and the number and size of sinkholes increase. Collapse of caverns and coalescence of sinkholes form larger, flat-floored depressions. Eventually, solution activity may remove most of the limestone from the area, leaving only remnants. Figure 5.39 C
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