EmeraldBay

GeologyMichael Hoenisch

Photos by Author

Field StudyFor this field study, I went through a couple of possible locations but finally landed on emerald bay. It was a hot day and I was able to get some jet skis from work so I

asked my roommate who is also in this class to come out and explore the area. I knew that there was a lot of glacial

activity in the area so I thought it would make for the perfect geological research venue. Not only is it a good place to

look at for geological purposes it is also an area flourishing with life. We encountered a ton of wildlife as well as plants

and some great views.

Background● Lake Tahoe was formed during

the pilocene and pleistocene (Monroe & Wicander, 2012).

● Down-dropped blocks in the sierras created the Lake Tahoe Basin when the pacific plate and the North American plate collided. (Gould)

● During a period between 3 million and 10,000 years ago the earth was going through a period of heating and cooling, creating large glaciers in the high altitude sierras. These glaciers rose and fell through time creating the lake we see today through glacial scraping. (TAS)

● Fanette Island was formed due to the hard granite it was comprised of allowing it to resist the glacial movement. (CA, 2013) Photo by Geosociety.

org

Rock Formations in the Bay

● As in most of Tahoe; Emerald Bay is comprised mostly of big granite Boulders.

● I did manage to find some quartz as well as shale while walking around on shore as well.

● To the right is a huge granite anorthosite wall we found.

● Below we have a general outline of the geological layout of the bay. It appears that the wall to the right may have been a part of the jurassic period. (CGS, 2007)

You can see Intrusions in the granite at the top left of possibly quartz minerals. We couldnt get close enough to investigate.Map by CGS

Shale● Shale is a fine grained clastic

sedimentary rock. It is comprised of muddy mix of clay minerals and tiny pieces of other minerals. (Blatt)

● Shale is the most common type of sedimentary rock. (Blatt)

● Shale is considered a mudstone because it is fissile and laminated. Laminated meaning that its made up of thin layers and fissile meaning that it breaks along the layers into thin pieces. (King)

● Shale containts many pieces of organic matter and usually fossil evidence. (King)

● It is also a very important source rock for oils.

Photo by author

Shale continued● The shale in tahoe was formed

due to the mass amounts of sediment left behind from the glaciers and rivers running through the lake tahoe basin.

● Shale is easily breakable and hardly ever breaks the surface due to its fissible properties. (King)

● Shale is easily recognized by its dark shade and layered sides. If it breaks its easy to tell as it will sometimes form sharp point.

● You can see the sharp point on the edge of this piece of shale on the right.

In the close-up view you can see the different layers of the sediment and darker colors which lead to my conclusion that it was indeed shale. Photo by author

Igneous Granite/Quartz● Granite is what makes up the

majority of the rock in lake tahoe.

● Granite is a plutonic rock in which quartz makes up between 10 and 50 percent of the felsic components and alkali feldspar accounts for 65 to 90 percent of the total feldspar content. (King)

● Because of the visible elements granite must have come from below the earths surface and was uplifted and exposed after sedimentary erosion.

The rock on the right is a prime example of granite consisting of a large quantity of quartz as well as alkali feldspars which make up the spots on the rock. It was too hard of a rock for it to be marble. Photo by author

Quartz● Quartz is a mineral

found within shale and other igneous rocks.

● The picture to the right is a prime example of milky quartz with its cloudy white color.

● Milky quartz is the most common variety of crystalline quartz.

(Wiki)

The above piece of milky quartz was found at star lake and photographed by Igor Strbc.

Quartz like this can be found all over the tahoe basin.

To the right you can see a huge intrusion of quartz in

a piece of granite protruding from the dirt.

Mallard● The Mallard or "wild duck" (Anas

platyrhynchos) is a duck that resides in wetlands or any body of water really.

● The males have a bright green head and the females as pictured to the right are usually of a brown speckled color with a blue or green stripe towards the back of the body. (wikipedia)

I took this photo of a female mallard on the shore of emerald bay that was being fed by some careless tourists. Remember, dont feed the wildlife.

Mallard - Evolution● The modern mallard evolved very

rapidly during the late pleistocene. (wikipedia, 2013)

● The mallard is the ancestor of almost all ducks. (n.d.)

● Mallards evolved in the general area of Siberia and their fossils appear rather abruptly in the food remains of ancient humans and other remains in europe. (wikipedia)

A male Mallard

Bald Eagle● The bald eagle (Haliaeetus

leucocephalus), our national bird, is the only eagle unique to North America. (Rutledge)

● North America is by far their greatest stronghold for bald eagles. They flourish here in part because of the salmon. Dead or dying fish are an important food source for all bald eagles. (Rutledge)

● Eagles sit at the top of the food chain with a lifting power of 4 pounds (Rutledge)

● An eagles vision is more than 4 times better than a human with 20/20 making them great hunters. (Rutledge)

I took this photo of an eagle on the top right branch of the dead tree in the middle of the shot right after I saw it fly over my head in the bay. I have seen the huge nest full of baby birds in the past as well.

Bald Eagle Evolution● Between 144 million and 66 million years ago, during the Mesozoic era, the

first birds began to evolve. (pbs)

● The earliest known species of class Aves is Archaeopteryx lithographica, from the Late Jurassic. (Random)

● There is significant evidence that birds emerged within theropod dinosaurs.(Random)

● 36 million years ago, the first eagles descended from kites. First to appear were the early sea eagles, which — like kites — continued to prey on fish and whose feet were free of feathers, along with booted eagles, which had feathers below the knee. (PBS)

● No one is sure when exactly the bald eagle evolved but the oldest fossils of this magnificent bird are about a million years old. (pbs)

Polystichum braunii - Fern● After browsing thousands of

images of ferns it seems to my best judgement that the species of fern I found in the bay was a Polystichum braunii. Pictured on the right it is a green fern with single blades stemming from the branch having a light green stem.

Polystichum braunii Evo.● The oldest land plants visible to the naked eye showed up around Middle

Silurian (425 million years). (Hans Steur)● The oldest ancestors were called cooksania and had no seeds, no flowers

and no leaves.(Hans Steur)● It is not known with certainty which Devonian plants were ancestors of the

ferns. (Hans Steur)● A plant that was closely related had similar shape and was a Rhacophyton

condrusorum which was around during the Devonian period. (Hans Steur) ● Since then the fern has evolved into the plant that we see today. (Hans

Steur)

References● http://eh2o.saic.com/tiimsWebsite/Content/BasinTopics/geology/default.asp

● TAS. (n.d.). Retrieved from http://www.tahoeadventuresports.com/misc/tahoefacts.htm (TAS)

● Monroe, J., & Wicander, R. (2012). The changing earth. (6th ed., pp. 620-621). Belmont:

Books/Cole. (Monroe & Wicander, 2012)

● Gould, M. (n.d.). Retrieved from http://tahoe.usgs.gov/facts.html

● CA, S. P. (2013). Emerald bay state park. Retrieved from http://www.everytrail.

com/destination/emerald-bay-state-park

● CGS. (2007). Geological map of lake tahoe. Retrieved from http://www.quake.ca.

gov/gmaps/RGM/tahoe/tahoe.html

● Blatt, Harvey and Robert J. Tracy (1996) Petrology: Igneous, Sedimentary and Metamorphic,

2nd ed., Freeman, pp. 281–292

● King, H. (n.d.). Retrieved from http://geology.com/rocks/shale.shtml

● Wiki. (n.d.). Retrieved from http://en.wikipedia.org/wiki/Quartz

● Wikipedia. (2013). Mallard. Retrieved from https://en.wikipedia.org/wiki/Mallard

● (n.d.). Retrieved from http://www.allaboutbirds.org/guide/mallard/lifehistory

References● Rutledge, H. (n.d.). Retrieved from http://www.baldeagleinfo.com/

● Random. (n.d.). Retrieved from http://en.wikipedia.org/wiki/Evolution_of_birds

● pbs. (n.d.). Retrieved from http://www.pbs.org/wnet/nature/episodes/american-eagle/bald-eagles-evolutionary-ancestors/4274/

● Hans Steur. (n.d.). Retrieved from http://steurh.home.xs4all.nl/engevovar/eevovar.html