Transcript Chapter 5 Atoms to Minerals

Chapter 14
Groundwater
14.1
Water in the Ground
Some rainfall becomes runoff and some enters the
ground to be stored as groundwater.
One factor that affects the amount of water that
enters the ground is the type of rock or soil.
Other factors include climate, topography,
vegetation and land use.
Porosity
The amount of water soil or rock can hold depends on
the space between the particles.
A soil with high porosity has more empty space
between the grains.
Well sorted particles also have more space
between them.
Permeability
How easily water passes through a material describes
its permeability.
The larger the pore spaces and the further apart
they are allows for high permeability.
Materials like sand allow water to pass easily.
However, fine
grained clays
have very low
permeability.
The Water Table
When rain falls, it is absorbed by the ground in most
places.
The area that it travels down through is called the
zone of aeration.
Eventually it travels far enough down that it
reaches the zone of saturation.
How far down this zone
occurs depends on
climate, rainfall, slope,
soil thickness, etc.
In humid climates, the
saturated zone can be
very close to the
surface.
In desert climates, it may
be hundreds of feet
down.
Ordinary Wells & Springs
Long ago people knew they
could just dig down to the water
table to obtain clean water.
By digging a well, people could
lower buckets or use pumps to
bring this water up.
An impermeable rock ledge
on a hill can allow for a
natural spring to occur.
Here water can only travel
out the side of the hill.
Artesian Formations
Permeable layers of rock that store and carry
groundwater to supply wells are called aquifers.
Sometimes an aquifer dips between two
impermeable rock layers.
As water travels down
between these layers, an
opening will allow an
artesian formation. Here
great quantities of water
will rise from up from the
ground.
Hot Springs
Some ground water comes into contact with very
hot underground rock.
Some of this very hot
water makes it to the
surface in the form of
a hot spring.
Geysers
A geyser is a hot spring that
intermittently shoots hot water
and steam into the air.
Hundreds of feet below
the surface, water can
become very hot under
pressure. When this
pressure is released, a
geyser forms.
Old Faithful,
Yellowstone Park
Fumaroles
Fumaroles are steam vents where recent
volcanic eruptions have occurred.
In some places, this ground water can be used as a
geothermal energy source.
Questions
Porosity is the amount of water soil or rock can
1. _______
hold depends on the space between the particles.
2. How easily water passes through a material
describes its ___________.
permeability
3. Permeable layers of rock that store and carry
groundwater to supply wells are called _________.
aquifers
4. A _______
geyser is a hot spring that intermittently
shoots hot water and steam into the air.
14.2
Conserving Groundwater
Water Budgets
A budget
describes the
income and use
of something.
With water we have rain and snow fall.
The water can soak into the ground and be used by
trees and plants. Excess water will runoff and end up
in streams.
If trees and plants do not need as much water, like in
the winter, the ground stores water in a process
called recharge.
During recharge, the soil
is storing water. If rain
continues until the soil is
saturated there will be a
surplus.
Any time the water is
used by trees and plants,
we have usage.
If the need is
greater than the
rainfall, we will
have a deficit.
Groundwater Conservation
In many places, humans are using groundwater
faster than nature can replenish supplies.
In addition, pollution threatens groundwater as well.
Overuse of Groundwater
When groundwater supplies are depleted, the
water table drops.
This then lowers the water table.
Near coastlines, saltwater can then seep into fresh
water aquifers contaminating them
Another problem of
groundwater overuse
is subsidence.
When too much
groundwater is used,
the ground becomes
compacted to the point
ground level drops..
In the San Joaquin
Valley of California,
water overuse has
caused the ground
to sink 9 meters
Groundwater Pollution
Groundwater is recharged by rainfall seeping
down into the ground.
If there is any pollution present like oil from roads,
fertilizers and even sewage it ends up underground.
Over the years all kinds of toxic waste has been
absorbed into the soil.
Many people have had
to moved from their
homes due to carelessness in the past.
Questions
budget describes the income and use of
1. A _______
something.
2. If trees and plants do not need as much water,
like in the winter, the ground stores water in a
process called___________.
recharge
3. If the need is greater than the rainfall, we will
have a _______.
deficit
4. When too much groundwater is used, the
ground becomes compacted to the point ground
subsidence
level drops, this is called ___________.
14.3
Groundwater and Geology
Minerals in Groundwater
When water evaporates, it
leaves deposits behind.
Therefore, rainwater is pure.
When water seeps into the ground it
takes all of the dissolved minerals like
carbon dioxide with it.
Ground water that contains large
amounts of ions from dissolved
calcium from limestone is called
hard water
If you bath in hard water, the ions cause the
soap to form a scum.
Hard water in heaters
leaves deposits behind
called boiler scales.
Artesian water is usually
warmer and harder than
river water.
Mineral Deposits by Groundwater
When groundwater containing
dissolved minerals evaporates,
mineral deposits are left behind.
Geysers leave behind a white
porous substance called
geyserite.
Petrified wood is formed from
mineral deposits dissolved in
groundwater replacing tree cells.
Most importantly, ground water
deposits cement sand grains
together forming sedimentary
rock.
Mineral Springs
A spring with a high concentration of mineral
matter is called a mineral spring.
These springs can be the result of …
-water passing through easily dissolved rock
-water containing gasses that turn to acid
-really hot water that dissolves minerals
Some mineral springs are
safe and used at health
resorts. Some are highly
alkali and are poisonous.
Caverns
Limestone is a bedrock
that dissolves easily.
Carbonic acid (rainwater
mixed with CO2) dissolves
limestone the most.
As this rainwater flows
down into limestone
cracks, the openings
become more porous and
soon caves form
underground.
Karst Topography
Areas that are made of easy to dissolve rock like
calcite and dolomite, develop sinkholes.
Sinkholes form when rock underground is
dissolved away by rainwater and the overlying
rock collapses in.
Rivers in these areas
can run into sinkholes
and travel underground
for miles.
Many sinkholes are found in Kentucky,
Tennessee, Alabama and Florida due to karst
topography.
Over the years people have been hurt and
structures damaged due to sinkholes.
Questions
1. Ground water that contains large amounts of
ions from dissolved calcium from limestone is
hard water.
called _____
2. Ground water deposits cement sand grains
sedimentary rock.
together forming ____________
3. A spring with a high concentration of mineral
mineral spring.
matter is called a ________
4. As rainwater flows down into limestone cracks,
the openings become more porous and soon
caves form underground.
______
End