Geology field assignment - Spring 2014
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This document provides information about the geology, flora, and fauna of Lake Tahoe. It discusses how the lake was formed over 10 million years ago from fault lines. It describes some of the dominant rock types around Lake Tahoe, including igneous rocks like granite and basalt, as well as sedimentary sandstone. It also notes how some of the features around Lake Tahoe have changed over time, such as the clarity of the water declining due to pollution and the forest changing due to fires. It provides details on some representative species found in and around Lake Tahoe, including the Stellar Blue Jay, American Black Bear, Jeffery Pine tree, and Snow Plant.
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Geology field assignment - Spring 2014
- 1. Denise Gray Professor Lawler Geology 103 Field Assignment Lake Tahoe Geological Study Photo from Wikipedia.org
- 2. Table of Contents • History of Lake Tahoe California • Location & Fault lines of Lake Tahoe • Fauna of Lake Tahoe 1. Stellar Blue Jay 2. American Black Bear • Rocks of Lake Tahoe 1. Igneous – Granite - Basalt 2. Sedimentary – Sandstone 3. Metamorphic – cave rock (1st Change) • Clarity Of Lake (2nd change) • Forest Fires (3rd change) • Tree of Lake Tahoe 1. Jeffery Pine • Lake Tahoe Flora 1. Snow Plant 2. Green Leaf Manzanita • References
- 3. History of Lake Tahoe • Elevation : 6225 Feet • The Tahoe basin was formed over 10 million years ago • 63 streams flow into the Lake • 1 river flows out : Truckee River • Largest Alpine Lake in North America • Depth of Lake Tahoe is 1,645 feet • Formed over 2 million years ago • U shaped Valleys were formed during the Pleistocene – large glaciers grew and surrounded Tahoe. • Over 670 million years ago Lake Tahoe was shallow sea water, and part of the Super continent Pangea (210 mya) • Lake Tahoe is 22 miles long, 12 miles wide, and 22 miles of shoreline
- 4. Location and Fault lines of Lake Tahoe • Over 10 Million Years ago these active faults created a Valley Floor – Now known as Lake Tahoe • Lake Tahoe is a “geologic block faulting” type of lake
- 5. Stellar Blue Jay Lake Tahoe Fauna • Dark Blue with white/blue markings • Head and crest is black Evolutions of Blue Jay: Class: Aves Order: Passeriformes Family: Corvidae Genus: Cyanocitta Species: Cyanocitta Stellar • Perching Bird • Found in evergreen forests of western mountains in the US and Canada
- 6. American Black Bear Lake Tahoe Fauna Evolution of American Bear : Animalia => Chordata => Mammalia => Carnivora => Ursidae => Ursus => u.americanus • Bears are closely related to dogs • Tahoe Bears are accustomed to humans Kingdom: Animalia Phylum: Chordata Cluss: Mammalia Order: Carnivora Family: Urisidae Genus: Ursus Species: Americanus
- 7. Igneous Rock Granite Photo from Newark.osu.edu Rocks around Tahoe • Formed from solidification of molten rock • Granite although Igneous can also be metamorphic 2 Types of Igneous Rocks Intrusive • Diorite • Gabbro • Granite • Pegmatite Extrusive • Andesite • Basalt • Obsidian • Pumice • Rhyolite • Sconia
- 8. Shardartist.com Aphanitic Igneous Rocks - • Contains quarts and feldspar • Formed from lava sheets hitting water. Has a fine grain texture • Black specks are Olivine and Pyroxene Rocks around Tahoe
- 9. Basalt - Igneous Rocks Photo from Weekendhike.com Rocks around Tahoe • Volcanic • Formed by rapid cooling of basaltic Lava • 20% quartz • Magma came from erupting volcanoes during the Pliocene Epoch
- 10. Sedimentary Rocks Photo from Jjvphotos.com Rocks around Tahoe • Forms by the accumulation of sediments 3 Basic Types Clastic • Breccia • Conglomerate • Sandstone • Shale Chemical • Rock Salt • Some Limestone Organic • Coal • Some Limestone Clastic-formed from Mechanical weathering and debris Chemical –formed when materials precipitate from solution. Organic- formed from accumulation of plant and animal or debris Sandstone Rock
- 11. Metamorphic Rocks Metamorphic rocks changed by heat, pressure or chemical activity Photo from Sacbee.com Photo:Wiki.com Foliated rock is a product of differential stress that deforms the rock in one plane, sometimes creating a plane of cleavage. For example, Slate is a foliated metamorphic rock, originating from shale.
- 12. Cave Rock Metamorphic Rock • Once an active volcano • Poured Lava into the lake thousands of years ago • Over time erosion caused tunnels Tunnel was cut for traffic in the 1930’s Cave rock has changed over time…
- 13. Lake Tahoe Water Clarity has changed over time…..Over time the clarity of the water has changed due to: • Tourism • Car and traffic pollution • People • Animals • Weather The lake has experienced a decline in water clarity since the late 1960s. A plan to reverse this decline and restore deep water clarity to historic levels—is known as the Lake Tahoe Total Maximum Daily Load or TMDL— was adopted by the States of California and Nevada, and approved by the U.S..
- 14. Lake Tahoe’s forest has changed over time….Lake Tahoe’s forest has changed over time due to : • Fires • Pollution • People • Animals On June 24, 2007 Angora Ridge Forest Fire The fire burned 3,100 acres destroyed 242, residences and 67 commercial structures, and damaged 35 other homes.
- 15. Jeffery Pine – Pinus Jeffreyi • Discovered in Shasta Valley, CA in 1852 by John Jeffery • Oldest Jeffery Pine found in Tioga Pass, CA containing 813 rings Evolution • First Appearance of seeds in the Devonian Period – 400 million years ago • First Appearance of gymnosperms – during the Carboniferous Period – 325 million years ago • Gymnosperms did not need moisture to reproduce – they quickly migrated and become abundant – 250 million years ago • Most prominent tree of Lake Tahoe
- 16. Photo from Examiner.com Snow Plant Lake Tahoe Flora Specific name : Surcodes Senguinea Order: Ericales Family: Ericaceae Genus: Sarcodes Species: S. Sanguine • Gets life from fungi • Found near trees • 6-12 inches tube shape • Blooms May - July
- 17. Green Leaf Manzanita Lake Tahoe Flora Photo:Inaturalist.org Arctostaphylos Patula – Specific name • Native to Western North America • In the Spring pink flowers appear, with green berries that turn red when ripe • Berries consumed by animals and birds Species of manzanita – formed during the late Tertiary period
- 18. References Lake Tahoe Facts and Info: The geological History of the Lake Tahoe Basin Pellant,C. (2002). Rocks and Minerals (2nd ed.). New York, NY: Dorling Kindersley, INC. Geology.com – Identified rocks and minerals United States Department of Agriculture, Forest Service, Lake Tahoe Basin Management Unit, 2012 U.S. Geological Survey, Lake Tahoe. 2004