Transcript Groundwater - Choteau Schools

Chapter 9, Section 2

Groundwater


Water that collects in the pores
and empty spaces of soil and
rocks.
Estimated that 14% of
freshwater is groundwater.
◦ 30x more than that contained in
all lakes and rivers.

Permeability

Permeable
◦ Pores in rocks and soil are
connected.
◦ Water can flow through the rock
and soil.

Impermeable
◦ Pores are few in number or not well
connected.
◦ Groundwater cannot flow through
the rock or soil.

Groundwater
Movement


Groundwater will sink into the
Earth’s crust until it reaches
an impermeable layer.
At this point, the water begins
to fill up the pores in the rock.

Groundwater
Movement

Zone of Saturation
◦ Area where all the pores are filled
with water.

Water Table
◦ The upper surface of the zone of
saturation.

Aquifer
◦ A permeable layer of rock that
lets water flow freely.

Wells



A well must extend into the zone
of saturation to reach water.
A pump brings water to the
surface.
If the water table drops below the
depth of the well, the well will go
dry.
◦ This can occur during droughts or if
water is removed from the well at a
quicker pace than it can be replaced.
◦ If the pore spaces in a larger area
remain dry over an extended period
of time, the land will sink.

Wells

Artesian Wells
◦ A well in which water rises to the
surface under natural pressure.
 Doesn’t need a pump.
◦ Aquifer for the well is located in
between two sloping impermeable
layers.
 Water enters the higher end of the
aquifer and puts pressure on the water
in the lower end of the aquifer.
 If a well is drilled in the lower end of
the aquifer, the water will naturally
move up the well.

Springs



Found on hillsides or other
areas where the water table
meets a sloping surface,
allowing ground water to flow
onto the surface.
Water is usually cool because
of the insulating qualities of
the rock and soil in which it
was contained.
If the water is heated by nearby
magma, the water comes to
the surface as a hot spring.

Geysers


A hot spring that periodically
erupts.
How it works:
◦ Groundwater is heated to high
temps causing it to expand.
◦ The expansion forces some of the
water out of the ground which
drops the pressure on the
remaining water.
◦ The drop in pressure causes the
remaining water to quickly boil
and produce steam.
◦ The steam and any remaining
water shoot out of the ground.

Cave
Formation



Water mixes with carbon
dioxide gas to form carbonic
acid.
Acidic groundwater moves
through pores and cracks in
limestone, dissolving the rock.
Eventually a cave is formed.

Stalactites
and
Stalagmites



Formed by deposits of calcium
carbonate that have been
dissolved from limestone.
Calcium carbonate is left
behind in a cave when water
evaporates.
Stalactites
◦ Hang from ceilings

Stalagmites
◦ Grow on the floor

Sinkholes


A depression that forms when
the roof of a cave collapses or
when material near the surface
dissolves
Form in areas with lots of rain
and lots of limestone (like
Florida and Kentucky)