MondayMarch 7, 2011(Groundwater –
Environmental Effects and Geologic Work)
The Launch PadMonday, 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.
Announcements
We will have a test this Friday.
Assignments For This Six-Weeks Date Issued Date DueVideo Quiz - Lakes, Rivers, and Other
Water Sources 2/27 2/27
WS - Running Water and Groundwater (Part 1) 2/25 3/4
PowerPoint Project – Rivers (P5 only) 2/28 3/3
WS - Running Water and Groundwater (Part 2) 3/2 3/9
Video Quiz - Groundwater 3/3 3/3
Complete WorksheetRunning Water and
Groundwater (Part 2)
Some localities are concerned with possible contamination of their groundwater supply.
Environmental Problems Associated
with Groundwater
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.
B. As the discharge from the septic tank
percolates through the permeable
sandstone, it is purified in a
relatively short distance.
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.
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 TopographyKarst 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 TopographyCommon 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
Figure 5.39 C
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.
VideoGlacier Power
Giant Glaciers - Wild New World - BBC Planet (5th period only)
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