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South Lake Tahoe A field study By Crystal Brown

Geology 103 Field Assignment Powerpoint

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Geology 103 Field Assignment Lake Tahoe by Crystal Brown

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Page 1: Geology 103 Field Assignment Powerpoint

South Lake Tahoe A field study

By Crystal Brown

Page 2: Geology 103 Field Assignment Powerpoint

Sierra Nevada Mountain RangeUntil about 130 million years ago, the place that the Sierra Nevada mountains now sit was completelycovered by an ocean (Ride).

Plate tectonics began to shift and the Pacific Plate dropped under the North American Plate. During the Paleozoic era, the pressure and friction caused the crust to melt and liquid plutonic rock to float towards the surface. This rock hardened to form the granite that makes up much of the rock these mountains consist of today.

The crash of the two plates also caused enough force to uplift the land. This formed the mountains

that we now know as the Sierra Nevada Mountain Range (Ride).

Page 3: Geology 103 Field Assignment Powerpoint

Lake Tahoe’s Water SourcesLake Tahoe has many different water sources. Lake Tahoe is so clear due to the fact that 40% of it’s water comes directly from rain and snow fall (Ride).

Also, the water that comes from streams goes through a natural filtrationsystem. The streams go through meadows and marshes. This process removes much of the dirt and prevents it from reaching the lake. The lake only has one river outlet

called the Truckee River and keeps its level mostly through evaporation (Ride).

However, lack of rain or snow has caused the lakes level to visibly drop at times as well.

*These pictures are from EagleFalls

Page 4: Geology 103 Field Assignment Powerpoint

Mallard Duck

The mallard duck is very common and can be found in almost any wetland environment. They have adapted enough to be found in various places around the world (“All”).

The mallard duck is the ancestor of nearly all domestic duck breeds. Because of this, they have evolved into several different looks and may be difficult to identify.

They have changed and evolved enough over time to have created completely different species of ducks. For example, the Mexican Duck is closely related to them although they are considered a different species (“All”).

Page 5: Geology 103 Field Assignment Powerpoint

Jeffrey Pine

The Jeffrey Pine is closely related to , and at first mistaken for, the Ponderosa Pine. However, this tree has learned toadapt to harsh climates unlike the Ponderosa (Jenkinson).

The Jeffrey Pine has evolved to be able to withstand harsh wintersand infertile sites. It can survive through droughts and cold winters.

The reason for it’s unique ability to adapt to multiple conditions and environments is due to it’s shorter growing season than other trees (Jenkinson). This trees ability to adapt to the cold winters and hot, dry summers of Lake Tahoe makes this tree one of the most common in the basin.

Page 6: Geology 103 Field Assignment Powerpoint

Granite Igneous Rock

The most common rocks of the Sierra Nevada Mountains isGranite, a type of igneous rock (“Rocks”).

This rock formed from slow cooling magma when the basinwas created.

It is identified by it’s grains that are visible to the naked eye.

It is composed mainly of quartz andfeldspar as well as minor amountsof other minerals (“Rocks”).

They occur underneath the Earth’scrust and take a long time to form from the slow cooling process.

Page 7: Geology 103 Field Assignment Powerpoint

Granite with xenoliths

An xenolith is a rock fragment that becomes trapped in another rock while it is newly forming and cooling (Jones).

These pictures show gabbroic (closely related to basalt) xenoliths that are enclosed inside granite rock (Jones).

This means that the granite rock around the xenolith is younger than the gabbroic xenolith itself.

Page 8: Geology 103 Field Assignment Powerpoint

BasaltIgneous Rock

Basalt is another rock of the igneous rock type.

This rock is formed from lava that cooled quickly and is usually black or dark in color.

Basalt is the most common type of rock found under theEarth’s surface.

Basalt is fine grained.

If weathered, the rock can turn a lighter color. If broken open however, the inside would be darker than it’s surface. The picture on the right shows the blacker areas that have not been weathered yet (“Rocks”).

Page 9: Geology 103 Field Assignment Powerpoint

Conglomerate – Forming Environment

Around the river of Eagle Falls there are many small pebbles. They mainly seemedto consist of broken off granite, quartz, basalt, and sandstone (“Rocks”).

This environment is a primespot for conglomerate to develop.

If these pebbles are buried andlithified, these rocks may become part of a conglomerate, or sedimentary type, rock (“Rocks”).

Page 10: Geology 103 Field Assignment Powerpoint

Works Cited “All about Birds.” The Cornell Lab ofOrnithology. http://www.allaboutbirds.org/gui

de/mallard/lifehistory

“Rocks”. Geology.com. http://geology.com/rocks/granite.shtml

Jenkinson, James L. “Jeffrey Pine” Encyclopedia of Life. http://eol.org/pages/999

712/detailsLife

Jones, Noris W. “The Sierra Nevada Batholith.” Department of Geology. http://www

du/~cejones/GeoImages/3IntrusiveBodies/1Plutonsz/2SierraNevadaCloseUps.html

Ride, Sally. EarthKam. “The Sierra Nevada Mountains and Lake Tahoe” https://earth

kam.ucsd.edu/ek-images/investigating_images/lake_tahoe

Photos taken by Crystal Brown/Angelee Brown