Transcript Geology of the Sierra Nevada Mountain Range

Geology of the Sierra Nevada
Mountain Range
By Elena Kurbatova
South Lake in the Sierra Nevada Mountains,
courtesy of Duane Shoffner
Geological History
Late Jurassic, Cretaceous, and Tertiary Periods
• Kula and Farallon plates are subducted under
the North American plate.
• Hot felsic magma coming from the mantle
starts rising, producing a chain of volcanoes
on the continent.
• Volcanic eruptions produce layers of solidified
magma, most of which stays deep below the
surface and forms plutons of solid granite.
Subduction of the Farallon Plate beneath the North American
continental margin, 140-100 million years ago.
Late Cretaceous Period
• Plutons come together to form the single,
massive batholith (deeply imbedded rock).
• Batholith begins to rise.
• The layer of marine sedimentary rock that lay
over the mountain is gradually eroded away
and deposited in the valley.
• The granitic core of the range is exposed.
Granite is exposed
Tertiary Period
• The continental crust east of the Sierra
Nevada begins to stretch in an east-west
direction.
• The crust breaks into a series of north-southtrending valleys and mountain ranges—the
beginning of the Basin and Range province.
• The Sierra Nevada Range starts rising along its
eastern margin.
What might have caused the uplift:
• The oceanic plates are subducted and become
completely overridden.
• The North American and Pacific plates come into
direct contact for the first time.
• Shear replaces compression as the North American
plate begins interacting with the Pacific plate.
• On the other side of the Sierra Nevada Range Basin
and Range Province is being pulled apart.
Faulting
The Sierra Nevada Faults
• The Sierra Nevada Fault is a normal fault
produced by tension
• There is also a smaller strike-slip fault
produced by shearing stress
The Sierra Nevada is an enormous tilted fault
block
Quaternary Period
• Not long after the Sierra uplift begins, the
Earth cools.
• Glaciers grow in the Sierra highlands and make
their way down former stream channels,
carving U-shaped valleys.
• The combination of river and glacier erosion
exposes the granitic plutons previously buried,
leaving only a remnant of metamorphic rock
on top of some of the Sierra peaks.
What makes the Sierra Nevada Range
geologically interesting
• Gold deposits in the foothill metamorphic belt
• A possibility of a major earthquake along the
fault line
• The unpredictability of the future plate
movement
Web sites consulted
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Sierra Nevada Physical Geography Joel Michaelsen
http://www.geog.ucsb.edu/~joel/g148_f09/readings/sierra_nevada/sierra_nevada.html
Sierra Nevada Mountains (Geology)
http://www.knowledgerush.com/kr/encyclopedia/Sierra_Nevada_Mountains/
America's Volcanic Past
Sierra Nevadas
http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Places/volcanic_past_sierra_nevadas.html
Pacific Mountain System
http://www.nature.nps.gov/Geology/usgsnps/province/pacifmt.html
GEOLOGY OF THE SIERRA NEVADAS Mary Ann Resendes
http://www.sierrahistorical.org/archives/geology.html
Geology of Yosemite
http://www.nps.gov/yose/naturescience/geology.htm
California Geological History
snobear.colorado.edu/.../CaliforniaMtns/California_geologic_history.pp