A COMMON TOPOGRAPHIC FEATURE EFFECT BY POROSITY AND PERMEABILITY IS……
Karst Topography
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What is Karst topography?
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topography developed in areas underlain by carbonate rocks, including limestone and dolomite. Karst
topography includes features like caves and sinkholes and forms when limestone is slowly dissolved away by
slightly acidic groundwater.
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 Groundwater
mixes with carbon dioxide to
form carbonic acid.
 Limestone
is a rock that is easily dissolved
by carbonic acid.
 As
the acidic groundwater moves through
pores in limestone, the rock dissolves,
enlarging cracks until an underground
opening called a cave is formed.

Groundwater not only dissolves limestone
to make caves, but it also can make
deposits on the insides of caves.
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Water dripping from the cave walls
contains calcium ions dissolved from the
limestone. If the water evaporates while
hanging from the ceiling, the calcium
carbonate is left behind and builds up to
form a stalactite.
Where water drops fall to the floor, a
stalagmite forms.
Cave
Development
CAVE ENTRANCE
Disappearing Stream
NATURAL CHIMNEYS
NATURAL BRIDGE
 If
underground rock is dissolved near the
surface a sinkhole may form.


A sinkhole is a depression on the surface
of the ground that forms when the roof of
a cave collapses, or when rock near the
surface dissolves.
These are common in areas that have lots
of limestone and enough rain water to
keep the groundwater system supplied
with water.
Sinkhole
SINKHOLE
 Karst
topography is common in the
Valley and Ridge Province of Virginia,
where limestone is abundant.
KARST TOPOGRAPHY FEATURES
Human Impact on Groundwater

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Groundwater accounts for 20% of all water
used in the U.S.
Unwise use of this valuable resource can
damage or deplete groundwater reservoirs
Some of the problems related to groundwater
use include:
overpumping-lowering the water table
subsidence
contamination
Pollutants

Contaminants introduced at the land surface may
infiltrate to the water table and flow towards a point
of discharge, either the well or the stream.
A SOURCE OF GROUNDWATER
CONTAMINATION: SEPTIC TANKS
Contamination results in a decline
in water quality.
ANOTHER SOURCE OF POLLUTION:
STORAGE TANKS
YET ANOTHER SOURCE OF POLLUTION:
LANDFILLS
Groundwater Moves – Usually
Slowly