Amberrose Thornton Field Assignment Geology 103 Professor Lawler Spring Term 2014 Lake Tahoe A brief geological history of the Lake in the Sky Photo: A. Thornton, 2015
1. Amberrose Thornton Field Assignment Geology 103 Professor
Lawler Spring Term 2014 Lake Tahoe A brief geological history of
the Lake in the Sky Photo: A. Thornton, 2015
2. Contents Introduction Geological Formation of the Lake DL
Bliss State Park Eagle Rock McKinney Bay Rock Identification Flora
and Fauna of the Lake Tahoe Basin Current Status of the LakePhoto:
A. Thornton,
3. Introduction I chose to do my field study about Lake Tahoe,
in particular the west shore area because I live and work here. It
was really interesting getting to learn a little more about area
that I have been living in through this project. Lake Tahoe has a
very fascinating history through all aspects of its existence. From
its formation, to its first human inhabitants, to its present day
state of existence. The geological history the small area that I
decided to study for this project has inspired me to learn
more.
4. The Formation of Lake Tahoe 4 million years ago, the upward
thrust of surrounding mountains and the downward fall of the valley
bottom along these faults and formed a basin that created an
ancestral lake. 3 million years ago, etupting volcanoes created a
volcanic dam, which blocked the water outlet that is known as the
Truckee River, causing a much larger
5. The Formation of Lake Tahoe Eventually a new outlet was
eroded from the lava dam creating the present path of the Lower
Truckee River. Following the faulting and volcanic period of the
Basin, an Ice Age developed. Huge glaciers formed and moved down
the V-shaped canyons on the western side of the lake. These
glaciers scoured away loose rock and reshaped the canyons into
broad U-shaped valleys. The rock and gravel left behind at the
sides and end of these melting glaciers are called moraines. As
these glaciers melted away, they also left behind brilliant bays,
jagged peaks, glacial polished ridges and crystal clear lakes
(USDA, n.d) Tahoe is an ancient lake and at 2-3
6. Chambers Landing Homewood Ski Resort View of McKinney Bay as
seen from Eagle Rock Photo: A, Thornton, 2015 Between 7-15 thousand
years ago, an underwater earthquake likely triggered a massive
four-mile long underwater landslide on the West Shore This
landslide widened the lake by three miles, pushed debris nine miles
out into the lake and generated a catastrophic 300 ft. high tsunami
(Antonucci, 2011) McKinney Bay
7. McKinney Bay Landslide Video: Ward, S. n.d
8. Eagle Rock Eagle Rock is a phreatomagmatic volcanic vent
that erupted through gravels that were either water saturated or in
shallow lake water. It is composed of basaltic tuff breccia with
angular to rounded fragments of scoriaceous black basalt up to 50
cm, and sparse accidental clasts of andesite boulders and cobbles.
Inward-dipping stratification indicates intra-vent deposition.
There is a correlation of basalt at Eagle Rock with Pleistocene
flows that are widespread in areas near Tahoe City evidence that
Eagle Rock was overridden by glacial ice and partially buried
beneath moraines during Tahoe and possibly Tioga glaciations of
Blackwood Canyon. Here, at the mouth of the canyon, numerous
glacial erratics lie on top of Eagle Rock, including granodioritic
boulder
9. Eagle Rock
10. DL Bliss State Park
11. Rock Identification
12. Flora and Fauna of the Lake Tahoe Basin
13. Flora and Fauna of the Lake Tahoe Basin
14. Current Status of the Lake
15. Sources Schweickert, R., Lahren, M., Hawle, J., &
Kortemeier, W. (n.d.). Retrieved June 23, 2015, from
http://foundation.aapg.org/documents/Field_Trip_Presentation.pdf
Ward, S. (n.d.). Lake Tahoe Shelf Collapse Video. Retrieved June
19, 2015, from http://es.ucsc.edu/~ward/