Glaciation in the Sierra Nevada Geomorphic Province

    I am currently taking a Geology of California class for my minor.  Very interesting stuff.  Due to a trip to Sacramento a few weeks ago, I was unable to go to our field trip.  To make up missing the field trip, I had to write a paper about one of the Geomorphic provinces of California.  I chose to write about some of the Glaciation of the Sierra Nevada Mountains.

      I will say, this paper is not my best.  It can be way better.  My fault for doing it two days before it was due.  Even though it is not the best I can do, it does hold some interesting information.  As I have done with past research papers, I post it here just as a record of some of the work I have done in school.  Why not? 
Glaciation in the Sierra Nevada Geomorphic Province
John Trammell
California State University, San Bernardino
March 23, 2015
ABSTRACT
    The Sierra Nevada Mountains, a continuous range of high mountains extending 385 miles from the Mojave Desert to the Cascade Mountain Range (Raub, Brown, Post, 2006), has been continuously sculpted by glaciers since the last glacial period in the late Pleistocene.  From the U-shaped Yosemite Valley to the Arête of the Minarets, the evidence of the power glacial ice has in changing a landscape is breathtaking.  Since the last glaciation period, the glaciers of the Sierra Nevada have been melting.  Due to climate change, a result from increase in temperature caused by high levels of CO2 in the atmosphere, the remaining glaciers of the Sierra Nevada are melting at an alarming rate.  Within the next 100 years, today’s glaciers will disappear.  
LITERATURE REVIEW
    Quaternary Glaciation.  The last glaciation period Earth had experienced occurred  during the Pleistocene epoch 2,588,000 to 11,700 years ago.  About 30% of Earth’s surface was covered by ice.  During this time, the Sierra Nevada Mountains were covered by large alpine glaciers; some glaciers with the thickness of 4,900 to 9,800 feet. Alpine glaciers are formed at the high peaks of the mountains.  Snow accumulates at the peaks, and compacts into ice.  As the ice pack gets heavy, it begins to drift down the mountains.  The ice pushes and cuts through rock on its way down, reshaping the mountains forever (Latta 2014).  
    Geologists have studied specific areas of the Sierra Nevada to understand the glaciers of this time period.  After looking at strong evidence from Yosemite National Park, San Joaquin River drainages, Sequoia National Park, and Kings Canyon National Park on the central to southern region of the Sierra Nevada, it has been concluded that the Sierra Nevada Mountains were covered by one large continuous alpine glacier.  An estimate of 7,722 square miles of ice covered the Sierra Nevada during this period of glaciation; one third of the entire range.  Ice was present from elevations of 4,900 feet and above in the northern Sierras to elevations of 8,000 feet and above in the southern Sierras (Moore and Moring, 2013).  As the atmosphere's temperature began to rise, the glaciers began to retreat.  
    Glacial Evidence and Current Glaciers.  The last glaciation period left many clues for geologists to study.  Many different geological features display evidence of the presence of large bodies of ice in the Sierra Nevada.  Majority of the evidence of the Quaternary Glaciation period comes in the form of erosion caused from the glaciers.  Sharp peaks, steep canyons, moraines, cirques, horns, u-shaped valleys, arêtes, and over 7,000 lakes were created from these large glaciers (Moore and Moring, 2013).  Many of these lakes are created from moraines that have been deposited by the glaciers, which became dams, holding water behind them.  Scientists have been studying several different moraine deposits left behind when glaciers had receded.  National Geographic defines a moraine as material left behind by a glacier.  Materials are usually soil and rocks (National Geographic, 2015).  Moraine deposits are found on both the east and west side of the Sierra Nevada.  More moraine deposits are found on the eastern Sierras, due to the fact that the west side moraine deposits have slowly eroded away by rivers.  
    Geologists have found moraine deposits on top of each other.  This has caused the geologists to learn that there are sub-stages to the last glacial period.  Times when glaciers would grow and recede depending on the climate patterns of the area at that time.  These findings have changed our views on how different geological features in the Sierra Nevada were formed.  Yosemite Valley is a U-shaped valley, carved out my what is called the Yosemite Glacier during the last ice age.  The discoveries of these multiple moraine deposits suggests the valley was carved in two different sub-stages.  The east side of the valley was carved out during the sub-stage called the Wisconsin stage (which is considered the first sub-stage).  Moraine deposits were deposited near Bridal Veil Meadows.  Half dome, one of the most famous rock features in Yosemite, was carved during these stages.  The second sub-stage re-grew the Yosemite Glacier, which extended 10 miles south of Bridal Veil Meadows, down past the entrance of Yosemite National Park, in the current day community of El Portal.  This second sub-stage was named El Portal since the glacier terminated in that portion of the Merced Canyon (Matthes, 1929).  The El Portal sub-stage was renamed to the Sherwin stage (Latta, 2014).  Two other sub-stages were discovered from other moraine deposits in the Sierras.  
    Today, 497 glaciers and 788 small ice bodies that can be found in the Sierra Nevada Mountains (Raub et al., 2006).  500 years ago, we experienced a small  ice age, which formed the current glaciers of the Sierra Nevadas.  These glaciers sit in cirques, which were created by the glaciers of the Quaternary Glaciation Period.  In recent history, from the 1960’s to present day, these glaciers have experienced fast growth and receding periods due to severe droughts and record breaking rain/snow levels (Raub et al., 2006).  According to Portland State University, the Palisade Glacier is the largest in the Sierra Nevada today, covering only .31 square miles (Wikipedia), and the Lilliput Glacier is the smallest in the Sierra Nevada today, covering only 0.019 square miles (Wikipedia).  According to Wikipedia, the Lilliput Glacier is the most southern glacier in the United States.  
    Climate Change.  The average temperature of the planet has been rising since the Industrial Revolution.  In the past few decades, the amount of snowpack in the Sierra Nevada has decreased, which does not help the current day glaciers of the Sierra Nevada.  California is entering into it’s 4th year of the drought.  Snow levels are at an all time low.  Scientists are studying past records of the current glaciers to study the effects of Climate Change.  Yosemite National Park, which has glaciers in the high peaks, are currently being studied.  When John Muir explored some of the glaciers in Yosemite in the 1870’s, they were at their maximum capacity to the time they were formed in the small ice age 500 years ago.  Because of the rising temperatures, the glaciers have dwindled to 55% of the size they were in the late 1800’s.  Just in the past 21 years, the world’s alpine glaciers have been melting faster than they are being replenished by new snow (Miller, 2013). If this trend continues, the glaciers of the Sierra Nevadas will melt away completely.  Two major issues will come from the disappearance of the glaciers in the Sierra Nevadas.  The biodiversity of the river systems in which the glaciers feed into will be harmed.  It is projected that a 11 to 38% drop in invertebrates will occur, due to less available habitat for insect larvae to thrive.   Many may not view this as a big issue, but small changes in the beginning of the food web can cause major issues higher up.  The obvious issues with the lack of glaciers is California’s water supply.  Major cities like Sacramento, San Francisco, and Los Angeles will be greatly affected by the lack of snowpack.   Agriculture in the Central Valley will also suffer from the impacts of Climate Change (Miller, 2013).  
CONCLUSION
    Ice transformed the Sierra Nevada Mountain Range from a normal granitic mountain to a uniquely shaped range that attract millions of visitors a year.  The evidence of ancient glaciers brings scientists to the region so they can better understand the powerful force glaciers have on an environment.  The current glaciers holds the key towards understanding how climate change will modify the natural environment.  It is important to have glaciers in the Sierra Nevada Mountains, and many hope they will remain in the high elevations for many generations to come.


REFERENCES
Latta, M., 2014, Glacial History and Processes of the Sierra Nevada:
Matthes, F. E., Multiple Glaciation in the Sierra Nevada: Science, New Series, Vol. 70,
    No. 1803 (Jul. 19, 1929), pp. 75-76.
Miller, Jeremy., 2013, The Dying Glaciers of California, Earth Island Journal:
National Geographic Education, Encyclopedia- moraine:
    (accessed March 2015).
Moore, James, and Moring, Berry, 2013, Rangewide Glaciation in the Sierra Nevada,
    California: U.S. Geological Survey, Geosphere v. 9, no. 6, p. 1804-1818.
Raub, William, Brown, C.S., and Post, Austin, 2006, Inventory of Glaciers in the Sierra
     Nevada, California: U.S. Geological Survey Open-File Report 2006-1239, 232 p. 4
    plates.

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