EmeraldBayGeologyMichael HoenischPhotos by Author
Field StudyFor this field study, I went through a couple of possiblelocations but finally landed on emerald bay. It was a hotday and I was able to get some jet skis from work so Iasked my roommate who is also in this class to come outand explore the area. I knew that there was a lot of glacialactivity in the area so I thought it would make for the perfectgeological research venue. Not only is it a good place tolook at for geological purposes it is also an area flourishingwith life. We encountered a ton of wildlife as well as plantsand some great views.
Background● Lake Tahoe was formed duringthe pilocene and pleistocene(Monroe & Wicander, 2012).● Down-dropped blocks in thesierras created the Lake TahoeBasin when the pacific plate andthe North American plate collided.(Gould)● During a period between 3 millionand 10,000 years ago the earthwas going through a period ofheating and cooling, creating largeglaciers in the high altitudesierras. These glaciers rose andfell through time creating the lakewe see today through glacialscraping. (TAS)● Fanette Island was formed due tothe hard granite it was comprisedof allowing it to resist the glacialmovement. (CA, 2013) Photo by Geosociety.org
Rock Formations in theBay● As in most of Tahoe; Emerald Bay iscomprised mostly of big granite Boulders.● I did manage to find some quartz as wellas shale while walking around on shore aswell.● To the right is a huge granite anorthositewall we found.● Below we have a general outline of thegeological layout of the bay. It appears thatthe wall to the right may have been a partof the jurassic period. (CGS, 2007)You can see Intrusions inthe granite at the top left ofpossibly quartz minerals.We couldnt get closeenough to investigate.Map by CGS
Shale● Shale is a fine grained clasticsedimentary rock. It is comprised ofmuddy mix of clay minerals and tinypieces of other minerals. (Blatt)● Shale is the most common type ofsedimentary rock. (Blatt)● Shale is considered a mudstonebecause it is fissile and laminated.Laminated meaning that its made upof thin layers and fissile meaning thatit breaks along the layers into thinpieces. (King)● Shale containts many pieces oforganic matter and usually fossilevidence. (King)● It is also a very important source rockfor oils.Photo by author
Shale continued● The shale in tahoe was formeddue to the mass amounts ofsediment left behind from theglaciers and rivers runningthrough the lake tahoe basin.● Shale is easily breakable andhardly ever breaks the surfacedue to its fissible properties.(King)● Shale is easily recognized by itsdark shade and layered sides. Ifit breaks its easy to tell as it willsometimes form sharp point.● You can see the sharp point onthe edge of this piece of shale onthe right.In the close-up view you can see the differentlayers of the sediment and darker colors whichlead to my conclusion that it was indeed shale.Photo by author
Igneous Granite/Quartz● Granite is what makes up themajority of the rock in lake tahoe.● Granite is a plutonic rock inwhich quartz makes up between10 and 50 percent of the felsiccomponents and alkali feldsparaccounts for 65 to 90 percent ofthe total feldspar content. (King)● Because of the visible elementsgranite must have come frombelow the earths surface andwas uplifted and exposed aftersedimentary erosion.The rock on the right is a prime example ofgranite consisting of a large quantity of quartzas well as alkali feldspars which make up thespots on the rock. It was too hard of a rock forit to be marble. Photo by author
Quartz● Quartz is a mineralfound within shale andother igneous rocks.● The picture to the right isa prime example of milkyquartz with its cloudywhite color.● Milky quartz is the mostcommon variety ofcrystalline quartz.(Wiki)The above piece of milky quartz was foundat star lake and photographed by Igor Strbc.Quartz like this can be found all over thetahoe basin.To the right you can see ahuge intrusion of quartz ina piece of graniteprotruding from the dirt.
Mallard● The Mallard or "wild duck" (Anasplatyrhynchos) is a duck thatresides in wetlands or any bodyof water really.● The males have a bright greenhead and the females as picturedto the right are usually of a brownspeckled color with a blue orgreen stripe towards the back ofthe body. (wikipedia)I took this photo of a female mallard on the shore ofemerald bay that was being fed by some carelesstourists. Remember, dont feed the wildlife.
Mallard - Evolution● The modern mallard evolved veryrapidly during the latepleistocene. (wikipedia, 2013)● The mallard is the ancestor ofalmost all ducks. (n.d.)● Mallards evolved in the generalarea of Siberia and their fossilsappear rather abruptly in the foodremains of ancient humans andother remains in europe.(wikipedia)A male Mallard
Bald Eagle● The bald eagle (Haliaeetusleucocephalus), our national bird,is the only eagle unique to NorthAmerica. (Rutledge)● North America is by far theirgreatest stronghold for baldeagles. They flourish here in partbecause of the salmon. Dead ordying fish are an important foodsource for all bald eagles.(Rutledge)● Eagles sit at the top of the foodchain with a lifting power of 4pounds (Rutledge)● An eagles vision is more than 4times better than a human with20/20 making them greathunters. (Rutledge)I took this photo of an eagle on the top rightbranch of the dead tree in the middle of the shotright after I saw it fly over my head in the bay. Ihave seen the huge nest full of baby birds in thepast as well.
Bald Eagle Evolution● Between 144 million and 66 million years ago, during the Mesozoic era, thefirst 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 appearwere the early sea eagles, which — like kites — continued to prey on fishand whose feet were free of feathers, along with booted eagles, which hadfeathers below the knee. (PBS)● No one is sure when exactly the bald eagle evolved but the oldest fossils ofthis magnificent bird are about a million years old. (pbs)
Polystichum braunii - Fern● After browsing thousands ofimages of ferns it seems to mybest judgement that the speciesof fern I found in the bay was aPolystichum braunii. Pictured onthe right it is a green fern withsingle blades stemming from thebranch having a light green stem.
Polystichum braunii Evo.● The oldest land plants visible to the naked eye showed up around MiddleSilurian (425 million years). (Hans Steur)● The oldest ancestors were called cooksania and had no seeds, no flowersand no leaves.(Hans Steur)● It is not known with certainty which Devonian plants were ancestors of theferns. (Hans Steur)● A plant that was closely related had similar shape and was a Rhacophytoncondrusorum which was around during the Devonian period. (Hans Steur)● Since then the fern has evolved into the plant that we see today. (HansSteur)
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