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)