basin & range / mojave desert - cabrillo...
TRANSCRIPT
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Basin & Range / Mojave Desert
Basin & Range
vs. Great Basin
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An overview of the last horst
Basin and Range / Mojave Desert Summary:
• Granitic, volcanic, marine sedimentary,
non marine sedimentary, metamorphic
• Horst and Graben structure, fault block mountains. A recent geologic event
• Great Basin is part of this province
• The Basin and Range extends into
Nevada, Arizona, northern New Mexico, western Utah and southern Idaho
• Has very old and very young rocks
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The Colorado Plateau
130,000 square miles (337,000 square km)
Bryce Canyon National Park
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The Wave, a sandstone formation located on
the Colorado Plateau in the Vermilion Cliffs Wilderness Area, near the Arizona-Utah border.
The Great Unconformity within the Grand Canyon's Inner GorgeThe time gap within the contact is 1.2 billion years, more time than
it took to form all of the canyon's layers.
Grand Canyon National Park
Zion National Park
Colorado Plateau Summary:
• Mostly marine sedimentary and volcanic rock some
igneous and metamorphic rock
• A high standing crustal block of relatively
undeformed rocks, dissected by long north south
faults
• Consists of broad open folds, volcanic features and
consolidated sedimentary rock
• Approximately 5 million years ago the entire Rocky
Mountains and Colorado Plateau were uplifted
4,000 to 6,000 feet.
The Salton Trough
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Water from the Pacific ocean
flowed into the
rift valley, creating what is
now the Gulf of
California
Northern tip begins the Salton
Trough
162 mi.
North American Western Plate Boundary – Oligocene to Present
● Mud pots gurgle and bubble, a sign of the geological activity going on underneath.
● These mud volcanoes and pots are located in the Brawley Seismic Zone, an area 25
miles long that extends from Brawley through Calipatria up to Bombay Beach.
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Old Shoreline of Lake Cahuilla, Santa Rosa Mountains near the Salton Sea
Salton Trough Summary:
• Mostly non marine sedimentary and volcanic
rock at surface, marine sedimentary below
• A structural basin, a continental rift, the northern extension of the Gulf of CA
• Basin is filled with over 5 Kilometers of
marine and non marine sediment
• Fault scarps and rifts, high heat flow, seismic and volcanic activity common
Transverse Ranges
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The Transverse Ranges can be divided
into three main regions that share similar
geologic characteristics:
-Western Transverse RangesSanta Ynez Mountains, Mountains of Central Ventura County
-Central Transverse RangesSan Gabriel Mountains, Santa Monica Mountains, Channel
Islands, Los Angeles Basin
-Eastern Transverse RangesSan Bernadino Mountains and Little San Bernadino Mountains
Basins and Valleys
Santa Clara River
• 116 miles long
• Watershed is ~1,600 square miles
• Maximum annual streamflow ~109 cubic meters per year and ~100 million tons of sediment deposited in Santa Barbara Channel
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Satellite Image showing
airflow patterns of the
Santa Ana Winds in
Coastal Southern
California
Satellite Image showing the Santa Ana Winds and
their contribution to the spreading of wildfires in
Southern Coastal California
Transverse Ranges Summary:
• Only province with NE / SW structural trend
• All rock types common
• Rotated ~90 degrees clockwise from
Miocene to present
• Very old and young rocks, individual
mountain ranges have complex geologic
histories
Peninsular Range
map
San Jacinto & Elsinore Faults
CHANNEL ISLANDS
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Peninsular Range extends 880 miles south into Baja California
Southern Baja California Batholith
The Peninsular Range
Peninsular Range Summary:
• Over 140 miles long in CA, but continues
to 750 miles to south
• Granitic Rocks and Marine Sedimentary Rocks dominate
• San Jacinto Fault and the Elsinore Fault
are the dominating structural features
• Overall geologic history similar to the Sierra Nevada
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