Lake Tahoe

Field StudyGeology 103 Prof. Mark LawlerAugust 1, 2014

By: Cynthia Núñez

*Taken along the Tahoe Rim Trail

The Formation of Lake Tahoe

¨The Lake Tahoe Basin was formed by the rise and fall of the landscape due to faulting (Forest, n.d.).¨Two principal faults evolved: the eastern margin created the Carson Range, while the Sierra Nevada developed on the western side (Forest, n.d.). ¨ Lava flowing from Mt. Pluto on the north shore formed a barrier across the Basin's Truckee River.  Water from snowfall and streams flow into the Basin, gradually creating the lake several hundred feet higher than what it is now (Forest, n.d.).¨ A new outlet was eroded from the lava dam creating the present path of the Lower Truckee River (Forest, n.d.).¨After the faulting and volcanic period, an Ice Age developed (Forest, n.d.).¨Glaciers formed and scoured away loose rocks and reshaped the canyons into broad U-shaped valleys (Forest, n.d.).

*Picture taken in Nevada Beach

Size of the Lake

The Lake is the third deepest lake in North America.Its 22 miles long and 12 miles wide.The average depth of the is 1,000 feet (Forest, n.d.).

*Picture taken in Emerald Bay

The Jeffrey Pine Tree

It was discovered in Shasta Valley California by John Jeffrey in 1852 (Jenkinson, n.d.).Native to California, but ranges throughout Oregon, Nevada and Baja California (Jenkinson, n.d.).The Jeffrey Pine requires longer cold exposure for leader growth in the Spring (Jenkinson, n.d.).It completes annual top growth soon and enters dormancy earlier (Jenkinson, n.d.).It adapted to short growing season and it dominates in cold infertile areas (Jenkinson, n.d.). *Tahoe Rim Trail

ChipmunkSmall members of the squirrel family.They range from Canada to Mexico (National, n.d.).They can live in a variety of environments from alpine forest to shrubby deserts (National, n.d.).Some dig burrows, with tunnels and chambers to live in and others make their homes in nests, bushes or logs (National, n.d.).They are about 4-7 inches Their predators are hawks, foxes, coyotes, weasels and snakes (National, n.d.).The chipmunk gathers food on the ground, near bushes, logs, and rocks so it can hide (National, n.d.).Solitary creatures, but during the spring they mate and use a birdlike chirp as mating call (National, n.d.).

Andesite

I believe this rock to be andesite.

It’s an extrusive rock It’s a composition between

basalt and rhyolite (University, 2005).

The texture is porphyritic Usually are fine-grained,

prophyritic rocks (University, 2005).

*found along the Tahoe Rim Trail

Igneous Rock Granite

It’s a felsic igneous rock. They are light colored

because they contain mostly nonferromagnesian silicate minerals (Monroe, 2009).

The dark parts are biotite mica.

The white and orange parts are feldspars.

The glassy minerals are quartz.

(Monroe, 2009).

* Found along the Tahoe Rim Trail

Basalt

I believe this to be an example of basalt.

Basalt is an extrusive igneous rock.

It’s low in silica, dark in color, rich in iron and magnesium (Basalt, 2014).

Some are glassy while others are very fine-grained and compact (Basalt, 2014).

*Taken near Emerald bay trail

Sedimentary sandstone

Composed of sand-sized grains of mineral, rock or organic material (Geoscience, n.d.).

Contains a cementing material that binds the sand grains together (Geoscience, n.d.).

One of the most common sedimentary rocks.

The small grains have been reduced to its size by weathering and transported to their site by moving water, wind or ice (Geoscience, n.d.).

*Found along the Tahoe Rim Trail

Quartz

Very abundant mineral. It’s an important rock-

forming mineral. 12% of earths mass is

made up of quartz (Akhavan, 2012).

It’s more stable than other minerals.

*Found along the Tahoe Rim Trail

References

Akhavan, A. C. (2012). The Quartz Page: Quartz as a Rock-Forming Mineral. Retrieved July 31, 2014, from http://www.quartzpage.de/gen_rock.htmbasalt (rock) -- Encyclopedia Britannica. (2014, April 2). Retrieved August 1, 2014, from http://www.britannica.com/EBchecked/topic/54604/basaltForest Service. (n.d.). Lake Tahoe Basin Mgt Unit - Learning Center. Retrieved July 28, 2014, from http://www.fs.usda.gov/detail/ltbmu/learning/?cid=stelprdb5109570Geoscience News and Information. (n.d.). Sandstone: Sedimentary Rock - Pictures, Definition & More. Retrieved July 30, 2012, from http://geology.com/rocks/sandstone.shtmlJenkinson, J. L. (n.d.). PinusieffreyiGrev. Retrieved July 31, 2014, from http://www.na.fs.fed.us/pubs/silvics_manual/Volume_1/pinus/jeffreyi.htmMonroe, J. S., & Wicander, R. (2009). Paleozoic Life History. In The Changing Earth:Exploring Geology and Evolution (6th ed., p.97). Belmont, CA: Brooks/Cole.National Geographic. (n.d.). Chipmunks, Chipmunk Pictures, Chipmunk Facts - National Geographic. Retrieved July 31, 2014, from http://animals.nationalgeographic.com/animals/mammals/chipmunk/University of Auckland. (2005). Geology - rocks and minerals. Retrieved from http://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/andesite.html