Denise Gray Professor Lawler

Geology 103Field Assignment

Lake TahoeGeological Study

Photo from Wikipedia.org

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

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

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

Stellar Blue Jay

Lake Tahoe Fauna

• Dark Blue with white/blue markings

• Head and crest is black

Evolutions of Blue Jay:Class: AvesOrder: PasseriformesFamily: CorvidaeGenus: CyanocittaSpecies: Cyanocitta Stellar

• Perching Bird• Found in evergreen forests of

western mountains in the US and Canada

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: AnimaliaPhylum: ChordataCluss: MammaliaOrder: CarnivoraFamily: UrisidaeGenus: UrsusSpecies: Americanus

Igneous RockGranite

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

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

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

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 debrisChemical –formed when materials precipitate from solution.Organic- formed from accumulation of plant and animal or debris

Sandstone Rock

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.

Cave RockMetamorphic 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…

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..

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.

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

Photo from Examiner.com

Snow Plant

Lake Tahoe Flora

Specific name : Surcodes SenguineaOrder: EricalesFamily: EricaceaeGenus: SarcodesSpecies: S. Sanguine

• Gets life from fungi• Found near trees• 6-12 inches tube shape• Blooms May - July

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

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