Transcript California Geology - Porterville Unified School District

California Geology
*Earth’s crust is divided into several tectonic
plates that have moved over time across the
surface of the earth.
Tectonic Plates are made of layer called
lithosphere (crust and upper mantle)
*These plates "float" on a thin underlying layer
of magma in the upper mantle (asthenosphere).
California Mountain Formations
• Coastal Mountain Range
• Sierra Nevada Mtn. Range
• Subduction causes deep
ocean trenches
– off the coast of California.
• Heating caused by one
plate diving beneath
another forms volcanoes
and may result in a
curved chain (arc) of
volcanoes
• Mountains are formed
on the land
California has Earthquakes!
• Located where three
tectonic plates come
together.
– Pacific Plate (moving
towards the northwest
5.5 cm/year)
– North American Plate,
(moving more slowly
towards the west)
– Juan de Fuca Plate (small
plate subducting under
northwestern US)
San Andreas Fault
• Runs from the Salton Sea area
to San Francisco area
• Transform Fault (plates slide
past each other)
• “Big Bend” in the San Andreas
Fault, north of Los Angeles.
– Makes it difficult for the plates
to slide past each other easily.
– Stress builds up, then a big
earthquake occurs
California has Volcanoes!
• Cascade Range
– Lassen Peak and Mt. Shasta.
• Lassen Peak last erupted
between 1914 and 1917.
• Shasta has erupted at least
three times in the last 750
years, maybe as recently as
1786
– Past eruptions have sent
flows of hot volcanic gases,
ashes, cinders, and other
debris down the slopes.
California has Volcanoes!
• Long Valley, in the Mammoth area of the Eastern Sierra
– Located where magma from the mantle wells up into the
crust.
California Grasslands
• Grassland (rangeland)
resources
• Covers 25% of the state
• 90% of Calif. endangered
species live in grassland
• Forage (feed) for livestock
• Lost when grassland is
converted to cropland or
cities (urbanization)
California has Wildfires
• Fire is a natural part of
the grassland
ecosystem
• Lightening and human
activities can cause fires
• Wildfires occur because
people have prevented
fire for so long that
there is a lot of dead
plant material
California has Floods!
• Sacramento River used to flood
• Water flowed all the way
through the San Joaquin Valley
• Dikes and levees built to hold
water back so farms could be
made
Sacramento Bee January 14, 2011
• “California has more risk of
catastrophic storms than any
other region in the country –
even the Southern hurricane
states, according to a new
study released Thursday”
Dikes and Levees
• Dikes are built along a
river to protect the
buildings from flooding
Sometimes levees fail