Geology 103 Lab field assignment

1. Lake Tahoe
Annie Brejc
Emerald Bay at sunset

2. History Of Lake Tahoe
 The Basin was formed from the rising and falling of the
landscape due to faulting.
 24 million years ago, the Sierra Nevada block was formed
by uplifting
 The Carson Range is on the eastern side and the western
side consists of the Sierra Nevada range.
 Lava flow from Mt. Pluto created what we now call the
Truckee River (Geology of Lake Tahoe Basin).
 Melting snow and other water flows created lakes above the
Lake Tahoe.

3. History of Lake Tahoe
 An ice age developed after the volcanic period,
creating huge glaciers that moved down the canyons
that resulted in U-Shaped valleys (Geology of Lake
Tahoe Basin).
 These glaciers left behind the rigid mountains and the
beautiful bays that we have today.
 The Lake that we have today is the tenth deepest lake
in the world, with an average depth of 1,000 ft. (the
deepest measured is 1,645ft).

4. Lake Tahoe
Mount Tallac 9,738 ft
The picture on the left and right are captured off
Emerald Bay Road at sunset

5. Black Bear
 The evolution of bears started about 30 million years ago.
The developed from a family called Miacids
 There are three subfamilies within the bear family: Giant
Panda, the spectacled bear, and the real bears.
 The real bear species has strong claws and a robust body
(black bears).
 A bear’s diet is mainly vegetarian, though they are classified
as omnivores.
 Bears have been evolving for the last 5 million years and
have acquired a wide geological distribution (Bratpack).

6. Black Bears in Lake Tahoe
 In California there is an estimated 25,000 to 35,000
black bears.
 The male bear is much larger than the female, which
have an average weight of 300 pounds.
 They are very strong swimmers and tree climbers. Also
they can sprint up to 35 mph.
 Bears are hibernators, meaning that when winter is
approaching they begin to forage for food that stores
enough fat to allow them to survive 40 to 50 feet off the
ground all winter (Kumar 2017).

7. Black Bear
Black Bears are hard to capture but
these are pictures of different
colored black bears found in Lake
Tahoe

8. Jeffery Pine
 The Jeffery Pine is spread out from southwestern Oregon, to
western Nevada, and to Baja California.
 Jeffery Pines are slow growing and long lived conifers. They
are very tall reaching up to 200 feet and have a diameter of
up to 8.2 feet. The top of the tree is either rounded or long
and is symmetrical. They have a very thick trunk covered in
large plates of bark (Pinus Jefferyi).
 The needles of Jeffery Pins usually are in bundles of 3 and
stretch from 3-11 inches.
 The largest Jeffery Pine cones are found in the Reno-Tahoe
area. They have honeycomb-like pinecones that vary in size.

9. Jeffery Pine
 The Jeffery Pine sexually reproduces through seeds. The
seed may drop as far as 100 feet from the parent tree and
then due to weather is blown farther away (Delevoryas
2016).
 Jeffery Pines can survive in different types of soil. In the
Sierra Nevada range Jeffery pines grow in volcanic soils.
 Jeffery Pines originated about 400 million years ago with the
first appearance of a seed. Then came the gymnosperm,
which were dominant in the Mesozoic Era. Gymnosperms
are flowerless place and reproduced by an exposed seed
(Delevoryas 2016).

10. Jeffery Pine
Jeffery Pines
are found all
around Lake
Tahoe
These are in my backyard

11. Chipmunk
 Chipmunks are omnivores. Their diet consists of nuts,
seeds, insects, small frogs, worms, and bird eggs.
 Chipmunks will begin to collect food in the fall and store it in
their burrows for winter.
 They are small, striped mammals. They are quick on the
ground and are able to climb trees to retrieve seeds. They
are about 4-7 inches with a tail that is 3-5 inches and they
weigh from 1-5 ounces (Chipmunks 2018).
 Chipmunks live for about 3 years
 They are an important factor in seedling establishment.

12. Chipmunks
 Squirrels, and chipmunks (direct descendants) were
found in fossil remains dated back to 30 million years
ago.
 Originally from Eurasia, this species’ migrated through
the land connection between Alaska and Siberia that
existed nearly 7 million years ago. (Musser 2019).

13. Granite
 This rock is something I have seen my whole life, as it
is prevalent in my backyard.
 Granite is an igneous rock, which means at one point it
originated from volcanic deposits. As previously
described this is one of the remarkable features of our
local flora and fauna, coming from Mt. Pluto.
 My identification process was based on its physical
characteristics (colors) and its visible grain.

14. Granite
Found in Christmas Valley in Myers

15. Scoria
 This rock is igneous. It has little texture, and contains mostly
black/gray minerals which are visibly fine.
 This rock is soft, as it does not scratch fingernails at all when
testing it against them.
 There are some visible bubbles, smaller than a pea, but not evenly
distributed.
FoundbehindLake
TahoeCommunity
College

16. Sandstone
 This rock has a lot of texture, so it cannot be igneous. It looks like
many different colors and layers.
 It appears to be sedimentary as the edges are not smooth and
seem to have been affected by the environment. Layers appear to
be sandy or claylike, which I inferred from its brownish-gray
coloring.
 Grain size is not as fine as the previous rock, so I believe it to be
coarse. It scratches fingernails, so definitely not soft.
Found Behind
Lake Tahoe
Community
College

17. Law of Superposition
 The law of superposition states that
sediments/materials accumulate on top of each other,
and thus the oldest sediments would be at the bottom
of the stratified layer (Law of Superposition 2019).
 This is visible in Tahoe when at the bottom of the beach
by Cave Rock on US-50.

18. Disconformity
 This fault occurs when the same layering is present
both above and beyond the disconformity. This is
visible in the same cliffs described as the law of
superposition.
 This occurs in sedimentary layers, which are different in
age but which have similar or equal layering

19. References
 Bratpack, & Internetdiensten, B. (n.d.). The evolution of bear species. Retrieved from
https://www.bearsinmind.org/Page/The-evolution-of-bear-species
 Chipmunks. (2018, September 24). Retrieved from
https://www.nationalgeographic.com/animals/mammals/group/chipmunks/
 Delevoryas, T. (2016, October 18). Gymnosperm. Retrieved from https://www.britannica.com/plant/gymnosperm
 Geology of the Lake Tahoe Basin. (n.d.). Retrieved from
https://www.fs.usda.gov/detail/ltbmu/learning/?cid=stelprdb5109570
 Kumar, V., Lammers, F., Bidon, T., Pfenninger, M., Kolter, L., Nilsson, M. A., & Janke, A. (2017, April 19). The
evolutionary history of bears is characterized by gene flow across species. Retrieved from
https://www.nature.com/articles/srep46487
 Law of superposition. (2019, April 09). Retrieved from https://en.wikipedia.org/wiki/Law_of_superposition
 Musser, G. (2019, January 23). Chipmunk. Retrieved from https://www.britannica.com/animal/chipmunk
 Pinus Jeffreyi. (n.d.). Retrieved from https://www.fs.fed.us/database/feis/plants/tree/pinjef/all.html