Transcript California Geography

California Geology
Key concept:
Major features of California
Geography can be explained in terms
of plate tectonics.
Building California by Plate
Tectonics
• Many Years Ago California did not exist as
it does today.
• Nevada was thought by some scientists to
be the continent’s west coast.
• When Pangaea began to break up, the
North American plate moved west.
• The western part of the continent began a
subduction era.
• This Built California
Ancient Plate Boundaries
•
Three major plates influenced
California’s geological history
-North American Plate
-Farallon Plate
-Pacific Plate
• The Farallon Plate had convergent
boundaries on both east and west sides.
• As the Farallon plate subducted between the Pacific and North
American plates, it disappeared.
• Eventually the Pacific and North American Plates came
together, the boundary became a transform boundary.
Subduction and Volcanism
• The subduction of the Farallon plate had two
major results.
- It caused rock to melt.
- It caused chunks of rock to collide with North
American Continent.
Sierra Nevada Batholith
• Because of Subduction,
a large amount of
magma formed in the
lithosphere.
• The magmas solidified
and formed a batholith.
• A batholith is a large
mass of igneous rock
that forms below the
surface.
The Cascadia Subduction Zone
• Today the subduction
zone extends from
Northern California to
Canada.
• The result is a chain
of volcanoes that
extend the entire
distance.
• It is called the
Cascadia Subduction
Zone
• During subduction, pieces of rock are scraped off the
bottom plate, called accretion.
• They accumulate and eventually form mountain chains
called accreted terranes.
• California’s coastal mountains where formed by accreted
terranes.
• California’s gold was collected in its rocks this way.
San Andreas Fault System
• California is home to
the most famous
transform boundary in
the world.
• On land the fault
extends about
1000km, from U.S.
/Mexican border to
Northern California.
• The San Andreas is
thought to be a
system of faults.
Offset of San Andreas Fault
• The Pacific and N.
American Plate have
been sliding past
each other for many
years.
• Scientist study offset
by matching unusual
rocks separated by
the fault
• By measuring offset,
geologists estimate
the amount and rate
of movement along
the fault.
Compression in Southern California
• The San Andreas Fault bends around the Los
Angeles area.
• Because the fault is not a straight line, It is not
100% transform.
• There are parts of it that are convergent.
• The compression created the San Bernardino
and San Gabriel Mountains,
Plate Tectonics and California
Landscape
• Most of California's
landscape has been
formed by plate
tectonics.
• Even though most of
the motion along the
San Andreas is
transform motion,
compression has
caused uplift along
the plate boundary.
Plate Tectonics and California
Landscape continued
• Major rivers and
mountain valleys run
northwesterly,
because they run
parallel to the plate
boundary.
• The Transverse
Mountain ranges are
only mountains that
run East-West.