X: California Features
1.
What are the features of the California landscape?
California's
remarkable geology is the result of volcanic
and tectonic activity. Its majestic mountains
were shaped by glaciers during the ice ages
as well as by wind and rain. The scenic coastline
of California is continually shaped by the pounding
waves of the Pacific Ocean. California has a
wealth of mineral resources, including the rich
soil of the Central Valley, the gold of the
Sierra, and oil off the coast and in various
locations across the state.
California
can be divided up into 11 Geomorphic Provinces,
many which include volcanic features. The Provinces
are: The Sierra Nevadas, Cascade Range, Coast
Ranges, Transverse Ranges, Peninsular Ranges,
Klamath Mountains, Great Valley (Basin and Range),
Modoc Plateau, Mojave Desert, and Colorado Desert.
(Excerpts from: California Environmental Resources
Evaluation System (CERES) Website, 2003, California
Resources Agency, from the California Coastal
Commission's California Coastal Resource Guide,
and California State Geological Survey Website,
2002, "California Geomorphic Provinces
Note 36." )
[
California Map (geomorphic) ]
[
California Map (detailed) ]
[ United States
Map ]
2. California Disaster History
a.
Earthquakes
Most
of the earthquakes that happen in the continental
U.S. happen in California. Why is that so? California
contains the San Andreas fault, which is a transform
boundary where the North American plate and
the Pacific plate are sliding past each other.
[
California Earthquake Website http://www.scecdc.scec.org/eqsocal.html
]
Where
will earthquakes happen in California?
[
Map of potential earthquakes ]
b.
Volcanoes
Does
California have active volcanoes?
[
Map of extinct and dormant volcanoes]
Can
you predict the next volcanic eruption?
c.
Erosion caused by Rivers & Lakes
Erosion
caused by rivers and lakes in California have
changed the landscape.
[
erosion in California ]
from Steven Dutch, Natural and
Applied Sciences, University of Wisconsin -
Green Bay
d. Tsunamis
The
relative tsunami threat for local tsunamis in
California can be considered as being relatively
low because of the low recurrence frequencies.
Large, locally-generated tsunamis in California
are estimated to occur once every 100 years.
Thirteen possible tsunamis have been observed
or recorded from local earthquakes between 1812
and 1988. These tsunami events were poorly documented
and some are very questionable. There is no
doubt that earthquakes occurring along submarine
faults off Santa Barbara, could generate large
destructive local tsunamis. In fact in December
of 1812, local earthquakes occured, each capable
of tsunami generation. Perhaps the size of the
1812 tsunami was exaggerated in the historical
records, but one and possibly two large tsunami
events did occur in the area.
[
California Tsunami Risk (text) ]
e.
Glaciers
Today, California still has glaciers. There
are 107 cirque glaciers, 401 glacierets and
1 valley glacier. Mount Shasta hosts five glaciers,
including the Whitney Glacier ,
the largest in California.
[
Whitney Glacier ]
f.
Landslides
What
makes a hillside susceptible to landslide?
Landslides
occur when a heavy rainfall causes the soil
to slip. The landslide process consists of 3
parts:
1. Where – Maps
can show area of susceptibility, but not necessarily
run out.
(maps are from past soil slips and elevation
maps, where the slope of the hillside was analyzed.
Local observations are also a good source of
information.)
The feature that seemed to best determine the
possibility of landslides was what the underlying
bedrock formation was like.
2. When – This
is determined by rainfall rate and duration.
3. How big – In
this case how big is based is a function of
the type of landslide being studied –
for example, Soil Slip – Debris Flow
See
how scientists monitor landslides
[
via http://vulcan.wr.usgs.gov/Projects/CalifLandslide/Maps/landslide_monitor.html
]
