geology field assignment - spring 2014
DESCRIPTION
Field Assignment - Geology 103 - June 2014TRANSCRIPT
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