Transcript Slide 1

VOCABULARY CH. 16
Porosity
Permeability
Water Table
Groundwater
Aquifer
Output
Recharge Zone
Input
Hydrogeology
Artesian Formation Perched Watertable Hard Water
Cavern
Sinkhole
Stalactite
Stalagmite
Karst Topography
GROUNDWATER
OBJECTIVES
 Identify properties of aquifers that affect the flow of
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groundwater
Describe the water table and its relationship to the
land surface
Describe two land features formed by hot groundwater
Describe how water chemically weathers rock
Explain how caverns and sinkholes form.
Identify two features of karst topography
Properties of Aquifers
Groundwater is water that fills and moves between spaces in
rock and sediment. It is an important source of fresh water
in the U.S.
An aquifer is a body of rock or sediment in which large
amounts of water can flow freely or be stored.
Porosity is the amount of open space found in rock or
sediment.
Size of particles affect the size of space between them.
Large particles will have larger spaces.
Particle packing also affects porosity. Loosely packed
particles will have more open space and store more water
Grain shape affects porosity. Generally, the more irregular
the grain shape the more space between grains.
Permeability – the ability for water to flow through a rock.
Although a rock may have many pores or spaces, if the pores
are not connected the water will not flow through and would
not be permeable.
Sandstone, a rock made of coarse sediments, is very
permeable
Clay, made up of very fine flat particles, is basically
impermeable.
ZONES OF AQUIFERS
Zone
Zoneof
ofsaturation
aeration isisthe
thearea
areaabove
belowthe
the
water
watertable
tablethat
in
which
contains
themostly
spacesair
are completely filled with water.
GROUNDWATER MOVEMENT
ALakes
perched
and water
streams
table
form
forms
when
when
the water table
cannot
is reach
exposed
the
The
Impermeable
recharge
zone
rockiswill
thenot
area
allow
where
water
water
to enters
flow through
the aquifer
main
at earths
water
surface
table.
Water table
Recharge
zone
Impermeable rock
Perched water table
Lakes and streams
HOT SPRINGS AND GEYSERS
As the water cools, it deposits minerals along the
rim of the spring that can build up forming cones
or terraces. The deposit is a form of calcite called
travertine.
Hot springs form when water below the surface is heated
to near its boiling point and rises back to earths surface.
GEYSERS
Water seeps into the ground
through cracks in the Earth”s
surface. The water collects in
conduits that restrict the waters
ability to return to the surface.
This restriction causes pressure to
build up in the conduits.
GEYSERS
The water at the bottom of the
conduit begins to boil and rise
heating the water above it. Pressure
builds as restrictions keep it from
reaching the surface.
GEYSERS
As the water continues to boil it
reaches temperatures well above
the boiling point. Pressure
continues to build and steam
may be seen to exit from the cone
as well as some bubbling.
GEYSERS
The pressure builds to the point
where the boiling water is
pushed out of the conduit by the
steam that is below. The
superheated water below the
surface water now explodes out
of the vent creating a geyser.
GEYSERS
After the water in the top of the
conduit is pushed out, the pressure
is relieved and the eruption stops.
The cycle then begins again.
WEATHERING BY GROUNDWATER
As groundwater passes through permeable rock, minerals in
the rock dissolve. The warmer the rock and the longer it is in
contact with water, the greater the amount of dissolved
minerals.
As water passes through soil and organic material it combines
with carbon dioxide to form carbonic acid, a weak acid that
chemically weathers rock by breaking down the minerals in it.
Rocks rich in calcite, like limestone, are especially vulnerable
to chemical weathering. As water enters cracks in these rocks
and dissolves the minerals, the cracks widen and may
eventually form caverns.
CAVERNS
When water containing dissolved
calcite drips from the ceiling of a
limestone cavern, some of the
calcite is deposited on the ceiling
of the cavern. As these deposits
build up they will form a cone
shaped deposit called a stalactite.
Remember “C” for ceiling and
to hang on “tite”
CAVERNS
As water drips from the ceiling
and falls on the floor, calcite
builds up to form an upward
pointing cone called a
stalagmite.
Remember “G” for ground and
hold with “mite”.
If a stalactite and a stalagmite
grow until they meet together,
they will form a column.
CAVERNS
As water sinks
into the
ground and
dissolves the
limestone, it
can weaken
the rock
above the
cavern. If the
rock collapses
a sink hole
will form.
CAVERNS
A natural
bridge can
form when
part of a layer
of rock does
not collapse
with the rest
of the layer.
This occurs
on the surface
most often
between two
sinkholes.
CAVERNS
Flowstone covering the wall of a
cave where water seeps in.
An example of drapery
known a bacon strip
CAVERNS
Don’t let the smile fool you,
the water was cold, about 45
degrees.
Mr. Verlinde wants to say goodbye