geology of yosemite lakes park, ca (ylp)
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Geology of Yosemite Lakes Park (YLP) in Coarsegold, California
Yosemite Lakes Park (YLP) is
located in the Sierra Nevada
foothills about half way between
Fresno, California and Yosemite
National Park alone California
Highway 41. Photo Courtesy of www.city-data.com
The Sierra Nevada stretches for 400 miles along
the eastern side of California. It is the longest
and highest continuous mountain range in the
lower forty-eight states. It is a well-pronounced
asymmetrical mountain range with a steep east
escapement and a gradual westward sloping side
that extends into the broad San Joaquin Valley. A
large normal system fault along the eastern edge
of the Sierra Nevada, called the Sierra Nevada
Fault, began to uplift about 25 million years ago
at the end of the Oligocene epoch. The uplift
was due to a major change in the motion of the
North American plate. The Farallon oceanic
plate, that was being subducted under what
would become the Sierra Nevada Mountain
Range, was totally consumed into the subduction
zone (Huntington, 2001).
Photo Courtesy of http://geoinfo.nmt.edu/tour/federal/monuments/gila_cliff_dwellings/farallon_plate.gif
Prior to the subduction of the Farallon oceanic
plate, the Western North American Plate was
dominated by the Cordilleran Foreland Fold
and Thrust Belt (Constenius, 1996).
The Pacific plate that moved into its place was
moving in a different direction (northwest).
The new boundary between the North
American plate and the Pacific plate became a
strike-slip fault system known today as the San
Andreas. The change in motion from a
convergent to a lateral movement produced a
different stress on the Sierra Nevada region.
Since the Sierra Nevada initial begin, the uplift
has accelerated. It is estimated that the Sierra
Nevada uplifts at a rate of 4 centimeters for
every 100 years. The continental crust east of
the region began to expand and the Sierra
Nevada region began to rise. Below is a picture
of the uplift and tilt of the Sierran Block with
the east escarpment formed along the fault and
the gently sloping western side (Huber, 1989).
Photo Courtesy of http://www.yosemite.ca.us/library/geologic_story_of_yosemite/genesis.html
The Sierran Block is in the center of a
highly active geological area. To the
north is the very volcanically active
Cascade Mountain range; to the south
the Garlock Fault system running east
to west; to the east is the Basin &
Range province with many active fault
systems such as Eastern California
Shear Zone & Sierra Nevada Seismic
Belt; and, of course, the world famous
San Andreas Fault (Science Daily,
2005).
Photo Courtesy of http://geology.csupomona.edu/docs/stop2-3.htm
The Sierran Block is a large batholith that forms the core of the Sierra Nevada Mountain Range.
The batholith is composed of plutons that formed deep
underground during a magma intrusion event many
millions of years before the Sierra Block began to rise.
The extremely hot more buoyant plutons called diapirs
intruded through denser country rock and sediments, but
never reaching the surface. Additionally during the magma
intrusion, some magma reached the surface as lava flows,
but most of it cooled and hardened below the surface and
remained buried for millions of years. As the mountains
rose, erosion wore down the material that had covered the
batholith. The exposed portions are the familiar granite
peaks of the Sierra Nevada mountain range, but most of the
batholith remains below the surface
(http://www.indiana.edu/~sierra/papers/2008/nahler.html).
Photo Courtesy of http://www.geog.ucsb.edu/~joel/g148_f09/lecture_notes/sierra_nevada/sierra_batholith.gif
Half Dome Yosemite National Park
Photo Courtesy of http://www.yosemitehikes.com/images/half-dome-winter-sunset-700w.jpg
GraniteGranite comes from the Latin word "granum" (or grain) because of it granular texture. Sometimes members of this group are also called granitiods or quartz-feldspar-plutonic rocks. These are the most widely distributed plutonic rocks. Light colored mineral that is 20-60 % quartz, 40-80% feldspar and 0-20% dark minerals such as biotite, augite, hornblende, muscovite, apatite, zircon and/or magnetite. Feldspar, quartz and biotite (mica) are popularly considered to be the essential constituents of granite.
Quartz is the second most abundant mineral in the Earth's continental crust is made up of a continuous framework of SiO4 silicon–oxygen tetrahedral, with each oxygen being shared between two tetrahedral, giving an overall formula SiO2.
Feldspars , the most abundant mineral in the Earth’s continental crust (KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8) are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust. A mineral composed largely of linked chain of silica, aluminum and oxygen elements. Feldspar means "field crystal."
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula (Mg,Fe)3AlSi3O10(F,OH)2
(Schumann, 1993). http://www.granitebydesigns.com/images/products/1284025663Granite_Yosemite_P1160483.jpg
Granite of Yosemite Lakes Park, CaliforniaOn the left are three views of a same granite formation. Granite formation is located on Revis Mountain
Photo Courtesy of Don Parker. Photo Courtesy of virtual.yosemite.cc.ca.us/ghayes/
SUMMARY• Prior to the subduction of the Farallon oceanic plate, the Western North
American Plate was dominated by the Cordilleran Foreland Fold and Thrust Belt.
• Sierra Nevada Uplift is due to the Farallon Plate subducting under the North American Plate.
• It is estimated that the Sierra Nevada uplifts at a rate of 4 centimeters for every 100 years.
• The Sierran Block is a large batholith that forms the core of the Sierra Nevada .• The Sierra Batholith, containing plutonic rocks (igneous rock), ranging from
granite to granodiorite to diorite. • Sierra Nevada Mountain Range is dominated by exfoliating granite domes, i.e.
Half Dome. • Granite in YLP is composed of quartz, feldspar and biotite (mica).
References
Constenius, K. N. (1996). Late Paleogene extensional collapse of the Cordilleran foreland fold and thrust belt. The Geological Society of America Bulletin , v. 108 no. 1 p. 20-39 .
Editorial. (2005). Eastern California Shear Zone Puzzles Seismologists. http://www.sciencedaily.com/releases/2005/10/051019002624.htm: Science Daily.
Huber, N. K. (1989). The Geologic Story of Yosemite National park. Yosemite National Park: Yosemite Association.
Huntington, A. (2001). Yosemite National Park A Personal Discovery. Mariposa, California: Sierra Press.
Nahler, N. (n.d.). Creation of the Sierra Nevada Batholith . http://www.indiana.edu/~sierra/papers/2008/nahler.html: Indiana University.
Schumann, W. (1993). Handbook of Rocks, Minerals, And Gemstones. New York: HarperCollins Publishers and Houghton Mifflin Company.