California Content Standards
Focus on Earth Science
9a Students know the resources of major economic importance in
California and their relation to California’s geology.
9b Students know the principal natural hazards in different California
regions and the geologic basis of those hazards.
9c Students know the importance of water to society, the origins of
California’s fresh water, and the relationship between supply and need.
9d* Students know how to analyze published geologic hazard maps of
California and know how to use the map’s information to identify
evidence of geologic events of the past and predict geologic changes in the
future.
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California Is located in the Northern Hemisphere
above the 30°N latitude. This location puts
California within the prevailing westerlies wind
belt.
The winds in California generally blow from the
west, off the Pacific Ocean, to the east.
The local patterns of wind circulation are
determined by the state’s mountains and valleys.
Thus, you may encounter winds coming from
different directions.
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California’s western edge meets the Pacific Ocean
to form a coastline that is 1,350 km long.
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The ocean, is a major influence on California.
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A current called the California Current flows from
north to south along California’s coast.
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This broad, slow-moving, shallow current carries
cool water along the coast and moderates
California’s climate by cooling air that moves
across the Pacific Ocean into California.
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California is located near the place where three
tectonic plates meet.
These plates are the Pacific plate, the North
American plate, and the small Juan de Fuca plate.
Over time, the interaction of these three plates has
made California a mountainous state.
California has two major volcanoes—Mt. Shasta
(4,317 m above sea level) and Lassen Peak (3,187 m
above sea level). Both volcanoes are located in the
southern Cascade Mountains of northern
California.
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California can also claim the highest and lowest
points in the continental United States.
Mount Whitney in the Sierra Nevada has an
elevation of 4,421 m above sea level.
Badwater, a salty pool in Death Valley, has an
elevation of 86 m below sea level.
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The topography in California and California’s
location near the Pacific Ocean have created
diverse climate patterns in the state. The
climate in California ranges from cool and wet
to hot and dry. Rainfall paterns have a large
impact on California’s Climate
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Two air masses that most often cause rain in
California during the winter are the Maritime
Polar Pacific air mass and the Maritime
Tropical Pacific air mass.
These air masses enter the mid-latitudes, they
are driven across the Pacific Ocean toward
California by the winds of the prevailing
westerlies.
These air masses move over the Pacific Ocean,
they absorb moisture from the evaporation of
ocean water.
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Maritime Polar Pacific air mass moves
southeast toward California in the winter, the
air mass meets warmer air from the midlatitudes.
The air mass pushes the warm air upward and
forms a cold front. Rain often begins to fall
over the Pacific Ocean before the cold front
reaches the California coast.
If rain does not begin over the ocean, then
mountains will determine where rain will
occur in inland California.
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The California Coast Ranges and the Sierra
Nevada create rain-shadow zones.
Rainfall is heavy along the western side of the
Coast Ranges and the Sierra Nevada.
Much less rain, however, occurs on the eastern
side of these mountains. Thus, semi-arid
interior valleys and arid deserts have formed
on the eastern side of the mountains.
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Along a cold front, conditions that cause a lowpressure, counterclockwise circulation of the
atmosphere may develop.
The southern part of this circulation pattern
produces southwesterly winds. As these winds
move farther southward, they pull air from the
Maritime Tropical Pacific air mass into southern
California.
The result is warm, tropical rain in southern
California.
The name “Pineapple Express” refers to this
warm, moist air that comes from the Pacific Ocean
near Hawaii.
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Average annual precipitation in California,
which includes rain, snow, and other forms.
Mountains receive the highest annual
precipitation, and the rain-shadow valleys
receive very little precipitation.
Cold fronts move southward through
California, the cold air meets and mixes with
warm air. As the air warms, rainfall stops.
Southern California receives less rainfall than
does northern California.
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Mountains in the northwest corner of the state, more
than 305 cm (120 in.) of precipitation may fall during a
year.
In the deserts in the southeastern part of the state, less
than 15 cm (5 in.) of precipitation may fall during a
year.
In fact, differences in latitude can cause extremes in
precipitation.
In one year, for example, 409 cm (82.3 in.) of
precipitation was recorded in the Santa Lucia
Mountains along California’s central coast.
The town of Bagdad in the Mojave Desert of southern
California, however, received no rainfall for a period
of 25 months!
In California, average precipitation decreases
southward. In addition, average temperatures
increase southward because of a decrease in
latitude. Precipitation and temperature,
together with the elevation in different parts of
California, produce the climate zone
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There are a variety of climate zones in California.
These include Mediterranean climates such as
those found around the Mediterranean Sea in
southern Europe and northern Africa. Areas that
have a Mediterranean climate have mild winters
and warm, dry summers.
California also has a cold, highland/timberline
climate zone. This climate zone is found at the
highest elevations in the mountains.
Arid mid-latitude and low-latitude deserts are
located in southeastern California. These desert
climate zones are dry and have hot summers and
cool winters.
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California also has steppe climate zones.
Though quite arid, these climate zones receive
more precipitation than do the deserts.
In some parts of California, differences in
elevation are large enough to produce several
climate zones in a very small geographical
area.
For example, you could play volleyball on a
beach in Los Angeles and, within a two-hour
drive, ski in the mountains or climb rocks in
the desert.
California is located on the edge of the North
American continent near the point where three
tectonic plates meet. Because of its location,
California has a very complex geologic history.
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California began to form almost 2 billion years
ago. The geologic map of California shows rocks
that range in age from 1.8 billion years to the
present. California’s oldest rocks, however, occur
in only a few scattered locations in the
southernmost part of the state.
The oldest of these rocks are metamorphic gneisses
that are about 1.8 billion to 1.7 billion years old.
These rocks, were later intruded by magmas that
formed batholiths of granite and gabbro.
These batholiths range in age from 1.4 billion to
1.2 billion years. After they formed, these
metamorphic and igenous rocks were uplifted
and eroded.
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California is rich in natural resources. Some of
these resources are renewable.
Others are nonrenewable.
For those resources that are nonrenewable,
wise management is necessary if Californians
are to keep their present lifestyle.
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Most of the water in California comes from
rain and snowmelt.
This water flows to the ocean by way of
surface streams.
The water also percolates into natural
groundwater storage basins.
Californians get most of their water from
streams and underground basins.
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Surface water is a renewable resource that
meets about 60% of California’s water needs.
California is not water self- sufficient. In order
to meet present water needs, some water has
to be imported from outside the state.
Any future increase in population will require
either better conservation methods or an
increase in imported water.
The distribution of water in California is
unequal.
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Southern California must import much of its
water.
To be used in California households, surface
water must be free of stream pollution at its
source and must be protected from
contamination during its storage in lakes and
reservoirs.
It must also be treated before it is sent to
where it is needed.
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The remaining 40% of California’s water needs
are met by groundwater.
Groundwater is contained in aquifers.
In these aquifers, groundwater has collected in
sediment that has filled in basins between the
mountains.
The largest aquifer in California is the Central
Valley aquifer system.
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Groundwater in this aquifer fills a large basin between
the Coast Ranges and the Sierra Nevada.
The water from this system is used to irrigate
farmland in the Central Valley. The availability of
water has helped the Central Valley become the
largest producer of agricultural products in the United
States.
Most of California’s population centers are located
above aquifers along the coast. Groundwater in these
aquifers, however, can no longer meet the demand of
these growing populations.
Southern California meets some of its needs by using
water from northern California and the Colorado
River. Some of this water is transported through the
Los Angeles Aqueduct.
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Californians need fuel, heat, and electricity to
maintain their modern-day lifestyle. Oil and
natural gas are largely used to provide all
three of these needs.
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Oil and natural gas are nonrenewable
resources that are relatively abundant in the
state.
Nonrenewable resources are those that form at
a rate much slower than the rate at which they
are consumed.
Oil and natural gas provide 78% of all of the
energy used in California.
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The first successful oil well in California began
operating in 1865 in Humboldt County.
By 1930, major oil fields had been discovered
in Kern, Kings, Los Angeles, Santa Barbara,
and Ventura Counties.
The first offshore oil field to be developed in
the United States, near Santa Barbara, where
drilling began in 1896.
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Hydroelectric energy refers to electricity that
has been produced using falling water.
For this to happen, a river must be dammed to
create a lake. The water at the base of the dam
is then released through electric-generating
turbines, which generate electricity.
California has many operating hydroelectric
dams.
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Geothermal energy, a renewable resource, is
generated by the heat of Earth’s interior.
Steam is produced in places where groundwater
comes in contact with hot magma below Earth’s
surface. Wells can be drilled into the steam
sources. The steam is used by turbines to produce
electricity.
The largest geothermal field in California is The
Geysers.
The Geysers is located in the mountains near San
Francisco and supplies electricity to that city.
Today there is little possibility of finding new
geothermal energy resources in California.
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Wind energy is also a renewable resource, and
generating stations are being built in many of
the windiest places in California.
For the production of wind energy to be
economical, the power of the wind at a given
site must be more than 400 watts per square
meter.
There are very few places in California where
wind power is that high.
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Solar energy is a renewable resource that is
growing in use in California. In fact, California
has been a leader in developing solar energy
for electricity generation.
The largest solar electric generating plant in
the world is located in Kramer Junction in the
Mojave Desert.
Electricity generated by this plant is supplied
to the Los Angeles area.
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California leads the United States in the
production of nonfuel minerals. In 2004, more
than 1,100 mines in the state together
produced minerals valued at $3.61 billion.
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Sand and gravel are used mostly in the
construction industry and are mined from
quarries in river deposits.
During the winter, river flow brings new sand
and gravel downstream to replace the
quarried material.
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Portland cement is mixed with sand and
gravel in the construction industry to make
concrete.
Portland cement is made mostly of powdered
limestone mixed with clay, sand, and gypsum.
All of these components are obtained from
sedimentary rocks. The limestone is quarried
largely from deposits in southeastern
California.
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Diatomite is a fine powder that is very porous.
It is used in industry and in home swimming
pools to filter water.
Diatomite is made from microscopic marine
plants that have died and settled to the bottom
of the ocean.
On the ocean bottom, these plants
accumulated in thick layers.
The major diatomite deposits, which are
mined by open-pit methods, are found in the
Coast Ranges.
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Boron minerals are used to make glass,
fiberglass for insulation, water softeners, and
detergents.
These minerals occur as evaporate deposits in
salt lakes. Ulexite, is an economically valuable
boron mineral.
Some boron minerals come from Cenozoic
lakes. They are mined by using both open-pit
and underground methods.
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Other deposits are found in modern dry lakes.
Historic 20–mule teams, pulled wagons that
carried the boron mineral ore from dry-lake
deposits in Death Valley.
Some lake deposits are located below the
water table, where the minerals are dissolved
in salt solutions.
To reach the minerals, miners drill holes in the
lake sediment and pump the solution out.
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The rush for gold in California in the 1850s
brought California fame and led to early
statehood.
Gold is used in coins, jewelry, electronics, and
dentistry.
In California, gold is found in quartz veins in
Paleozoic metamorphic rocks.
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The gold is spread unevenly throughout these
quartz veins, which are mined by underground
tunneling techniques.
During the Eocene Epoch, the Sierra Nevada was
eroded down to the level of the gold-bearing
quartz veins. The gold was transported
downstream and deposited in river deposits. This
type of gold is referred to as placer gold. These
river deposits were mined by using high-pressure
water hoses.
Today, recreational miners recover gold from
river deposits by using small dredges to which
suction hoses are attached.
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Because of its diverse geology, topography,
and location, California is at risk for a variety
of hazards. Earthquakes, volcanic eruptions,
landslides, wave erosion, tsunamis, and
flooding are natural hazards that Californians
may face at some time.
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Earthquakes occur when rocks along a fault
suddenly move.
California experiences more than 30
earthquakes each day.
Most of these quakes are too small to
feel.Larger earthquakes are also common,
Movement along the subduction zone between
the Juan de Fuca and North American plates
causes some earthquakes both in the ocean
and on land along the coast of northwestern
California.
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Movement on the San Andreas fault boundary
between the Pacific plate and the North
American plate causes many other
earthquakes along a line that runs northwest
through the western part of the state
Most earthquakes happen along numerous
other faults in the state.
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In the past several thousand years, there have
been few volcanic eruptions in California.
But there are six places in the state where a
volcanic eruption is possible.
About 30% of California is located in a potential
volcanic hazard area. At all of these sites, recently
erupted volcanic rocks, hot springs, and geysers
indicate that hot magma is still beneath Earth’s
surface.
The eruption of Lassen Peak, lasted from 1914 to
1917. The largest single eruption during that
period happened on May 22, 1915.
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The powerful blast shot volcanic ash more
than 9,000 m into the air. The ash traveled as
far as Winnemucca, Nevada, which is 320 km
east of the volcano.
Lava melted snow on the ground, which
created a volcanic mudflow that traveled 16
km down Hat Creek.
Compared with other volcanic eruptions
worldwide, however, the May 1915 eruption
of Lassen Peak is considered a small eruption.
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California has relatively young, steep
mountains that often consist of soft, loose
sedimentary rocks.
These characteristics make parts of the state
prone to landslides.
Landslides are especially likely when rainfall
rates are high. The faster a hill is saturated by
rain, the more likely the hill is to suffer a
landslide.
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Hillsides are also made less stable if they are
steepened or undercut, either naturally by
rivers or artificially by construction projects.
A landslide in La Conchita, a coastal town
near Santa Barbara, is shown in Figure 5.
Landslides here are not just a modern
occurrence. Destructive landslides have been
reported in the La Conchita area since the
1880s.
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Wherever hills or mountains border the ocean,
sea cliffs will form as a result of wave erosion.
As time passes, waves will continue to
undercut a cliff and weaken it until it collapses
into the ocean. In this way, the ocean advances
and the cliff line retreats landward.
Different methods have been tried to delay the
process of coastal erosion.
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No method has been found to be effective in
stopping the force of wave erosion.
Roads and structures that are built on the
beach at the base of a cliff can be threatened by
wave action whenever storm waves and high
tide happen at the same time.
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Tsunamis can be generated when large
earthquakes shake the ocean bottom or when
large undersea landslides cause water along
the ocean bottom to be displaced.
Earthquakes at subduction zones and
landslides in ocean trenches are common
around the edges of the Pacific Ocean.
Therefore, parts of the California coastline are
subject to tsunamis.
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Eleven tsunamis large enough to cause
damage have been recorded in California.
The 1964 tsunami, which was generated by an
Alaskan earthquake, produced a maximum
wave height of 7 m in Crescent City.
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Evidence indicates that global warming is
increasing the rate at which glacial ice is
melting around the world. As the glacial ice
melts, sea level rises.
As a point of reference, if all of the glacial ice
in the world melted, sea level would rise about
70 m. If sea level rose this amount, some of the
Los Angeles basin, major portions of the cities
around San Francisco Bay, and about one-third
of the Central Valley could be flooded.
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If such a maximum sea level rise occurred, it
would take decades to happen.
Reducing global warming caused by human
activity may delay this hazard.