geology 103 presentation

1. LAKE TAHOE BASIN
GEOLOGY 103
COURTNEY SCHMIDT

2. Introduction
Moving from coast of Southern California to South Lake Tahoe, I never knew much about the
lake and why there are so many interesting qualities to it. I am interested in knowing what types of
geological activities have occurred to make this basin how it is today. This basin is known for its
clear, fresh water and for the unknowns that rest deeply below. I plan to do my observations by
walking around the basin to explore its rock formations, animals around and in the lake, and the
plants that make it so lively. I will go to a rock formation called “Party Rock” and “Cave Rock” to
look at geology formation evidence. Some animals I may not find, so I will have to depend on some
online research for those difficult to perceive.

3. ❖ Location: Sierra Nevada, Lake Tahoe
❖ Elevation: Highest peak is Freel Peak at 10.891 ft
❖ 24 million years ago: Sierra Nevada block formed from uplifting
❖ Came about 2 to 3 millions years old due to block faulting, where land moves up or down due to a
fracture in Earth’s Crust
❖ Geological History:
➢ Periods of marine deposition, granitic intrusion, tectonic uplift, volcanic eruptions, glacial
scouring, and erosion that have been repeated over a vast expanse of time
➢ Oldest rocks found were metamorphosed Paleozoic and Mesozoic volcanic and sedimentary
rocks that were intruded by the Jurassic and Cretaceous granitic rocks
(Schweickert et al., 1999)
Lake Tahoe Basin Formations

4. Lake Tahoe Basin Formations Cont.
➢ Three major faults in Tahoe
○ West Tahoe Fault
○ Incline Fault
○ Stateline Fault
➢ Faulting and volcanic activities occurred, then an ice
age happened
○ Ice age reshaped rocks and canyons
○ Water melted, creating the clear water found
(USDA, 2017) Picture of the Faults: Cazarez, S. (2012). Cochise
College Student Papers in Geology.
Retrieved June 24, 2017, from
http://skywalker.cochise.edu/wellerr/students/lake-tahoe/p
roject.htm

5. Rocks at the Lake Tahoe Basin
➢ Went to a rock formation called “Party Rock” finding these rocks typically
found at the Lake Tahoe Basin (all photos taken by me)
Igneous
Rock
(andesite):
cooling and
solidifying
magma or
lava, very
hard in
texture
Sedimentary
Rock
(sandstone):
deposition and
solidifying
sediments,
rough in
texture
Metamorphic
Rock
(Gneiss):
pressure,
heat which
formed the
layers, dark
bands

6. Rocks at the Lake Tahoe Basin
The rocks that I found:
Andesite
➢ Forms after an oceanic plate
melts during its descent into
the subduction zone to
create a type of magma.
➢ Usually found in lava flows
produced by
stratovolcanoes.
(geology.com, 2017)
Sandstone
➢ composed of
sand-size grains of
mineral, rock, or
organic material
➢ Most common type of
sedimentary rock
(geology.com, 2017)
Gneiss
➢ identified by its bands
and lenses of varying
composition
➢ Formed at convergent
plate boundaries
(geology.com, 2017)
The most common rock that I found was the igneous rock. There
must have been a lot of magma and lava activity in that area by
“Party Rock”.

7. Rock Unconformities in Lake Tahoe
Party Rock Driving by Cave Rock
Because of tectonic plates moving, there is a change that the rocks can change its form,
experience a lot of pressure which can compact them. (photo by me)

8. Unconformities
➢ Unconformities show erosion and nondeposition.
○ The fossil record shows itself incomplete in these areas
➢ Angular unconformities: older rocks dip at a different angle, than overlying
strata (Monroe & Wicander, 420)
Photo by Courtney Schmidt, taken
by Cave Rock

9. Flora at the Lake Tahoe Basin
Sugar Pine Trees (Pinus lambertiana)
➢ Found in the Sierra and Cascade mountain ranges
➢ Largest species of its genus
➢ 111 species of the genus Pinus
➢ Has the largest cone of any conifer species
➢ Lake Tahoe makes an effort to look for these trees that
have a resistance to the foreign blister rust
➢ Changing over time: Getting cut down by humans
(photo taken by me: pine tree by “party rock”) Info: (League, 2017)

10. Fauna: Lahontan Cutthroat Trout
Evolution: Listed as endangered on October 13, 1970 and reclassified as threatened in 1975
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Oncorhynchus
Species: clarkii
Subspecies: henshawi
Discovered in the 1800’s in Lake Tahoe and was fished a lot
These lake dwellers are 50 inches in length, weight up to 40 pounds and live up to 5-14 years. They eat
terrestrial and aquatic insects and smaller fish to survive. (service, 2014)
Fish in the Tahoe Lake:
Lahontan Cutthroat Trout. (n.d.). Retrieved June 25, 2017, from
http://www.northwestfishingreports.com/forum/viewtopic.php?f=38&t=11954

11. Fauna: Black Bear
-The black bear has a population of about 25,000 to 35,000
in California
- The fur of the black bear is often black but can range to
brown or occasionally blonde.
-Evolution of Adapting to Humans
-Can swim about a mile in the Tahoe Basin
(Rogers, 2012)
Ursus americanus
Kingdom: Animal
Phylum: Chordata
Class: Mammalia
Subclass:Theria
Infraclass:Eutheria
Order:Carnivora
Suborder:Fissipedia
Family:Ursidae
Subfamily:Ursinae
Subgenus:Euarctos
Species:americanus
Black Bear sighting in the
Tahoe camp group

12. Principles of Relative Dating
Law of Superposition
➢ Youngest rock on the bottom, oldest on top
➢ Because of the uplifting and the constant changes of the Lake Tahoe Basin, it may be hard to use
Law of Superposition to date rocks. I do know that there are rock formations in Lake Tahoe that still
hold their layers that could help date rocks for geological purposes.
Eagle Lake shows the different
layers of rock.
Eagle Lake Buttress. (n.d.). Retrieved June 25,
2017, from
http://www.aboutlaketahoe.com/climbing/eagle-l
ake-buttress.htm

13. Changes: Land, Water, Ecosystem
➢ Because of humans ‘wastes increasingly going to the Lake Tahoe Basin, water
clarity is decreasing a foot per year.
➢ The pollution that humans create make it impossible for water to infiltrate the
soil. This creates a run off, causing many erosions.
➢ Many people are working to “Keep Tahoe Blue” and making many laws of
what humans can and cannot do by or in the lake.
➢ Evolution, “changes over time”, not only happen naturally, but humans have
impacted the evolution of fauna and flora
(Raumann, 2003)

14. References
Andesite. (2017). Retrieved June 24, 2017, from http://geology.com/rocks/andesite.shtml
Cazarez, S. (2012). Cochise College Student Papers in Geology. Retrieved June 24, 2017, from http://skywalker.cochise.edu/wellerr/students/lake-tahoe/project.htm
Classification of Black Bears. (n.d.). Retrieved June 25, 2017, from https://www.bear.org/website/bear-pages/black-bear/basic-bear-facts/35-classification-of-black-bears.html
U. (n.d.). Geology of the Lake Tahoe Basin. Retrieved June 24, 2017, from https://www.fs.usda.gov/detail/ltbmu/learning/?cid=stelprdb5109570
Gneiss. (n.d.). Retrieved June 25, 2017, from http://geology.com/rocks/gneiss.shtml
Lahontan Cutthroat Trout. (n.d.). Retrieved June 25, 2017, from http://www.northwestfishingreports.com/forum/viewtopic.php?f=38&t=11954
League. (2017). Animals and Plants. Retrieved June 24, 2017, from https://www.keeptahoeblue.org/abouttahoe/animals-plants
McLaughlin, M. (2017). Tahoetopia. Retrieved June 24, 2017, from http://tahoetopia.com/news/three-faults-under-lake-tahoe
Monroe, J. S., & Wicander, R. (2015). The changing earth: exploring geology and evolution. Stamford, CT: Cengage Learning.
Raumann, C. G. (2003, October). Geographic Research at Lake Tahoe - USGS. Retrieved June 25, 2017, from
https://www.bing.com/cr?IG=F91C4067FA7243EC80BBB9F89E97CE63&CID=052AB73E519C62583DE2BD92509A63D1&rd=1&h=2fGcZ0VxbC0tHNUGJgmepxGK_xbpi20ZfAgR3vpAaz
Q&v=1&r=https%3a%2f%2fgeography.wr.usgs.gov%2fscience%2fdocs%2ftahoe_fact_101-03.pdf&p=DevEx,5061.1
Rogers, L. L. (2012, February 3). Quick Black Bear Facts. Retrieved June 24, 2017, from
https://www.bear.org/website/bear-pages/black-bear/basic-bear-facts/168-quick-black-bear-facts.html
Schweickert, R. A., Lahren, M. M., Smith, K., & Karlin, R. (1999). Preliminary Fault Map of the Lake Tahoe Basin, California and Nevada. Seismological Research Letters, 70(3), 306-312.
doi:10.1785/gssrl.70.3.306
Service, U. F. (2014, April 16). Lahontan cutthroat trout. Retrieved June 24, 2017, from https://www.fws.gov/nevada/protected_species/fish/species/lct.html