Field assignment

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Transcript of Field assignment

  • 1. The South Lake Tahoe Area

2. Lake Tahoe: the beginning

  • Taking this class over the summer really made me start to think differently about things I see all the time. For example, Lake Tahoe. Ive seen it numerous times, but it was not until this class that I wondered how did it get here?

3. The first thing I learned was that, unlike many of the surrounding Lakes, Lake Tahoe was NOT formed by glaciers 4. though the glaciers did have an effect, raising the water level by 800 ft(Antonucci 2011)
5. How was the lake formed?
About 4 million years ago, a system of parallel faults caused an upward thrust, creating the surrounding mountains, and a downward fall of the valley bottom that formed the basin that would become Lake Tahoe
Erupting volcanoes blocked the river channel which caused the water to become trapped
It became a lava dammed lake
Around 15 thousand years ago an underwater earthquake triggered a massive underwater landslide that widened the lake by 3 miles and explains the bulge on the west shore
Waves, tsunamis and damming by humans has created the Lake we see today
(Antonucci 2011; Alt 1995)
6. The Lake Today
Because Lake Tahoe is 2-3 million years old, it is among the 20 oldest lakes in the world
Its avg. depth is 1,027 feet, the max depth is 1,645, feet making it the 2nd largest lake in the U.S.
The lake holds 39 trillion gallons of water, enough to completely cover the entire state of CA in a foot of water
The water coming from rain and snowmelt runoff
(Antonucci 2011)
7. The Ponderosa Pine(Pinus ponderosa)
I came across this tree when I was out hiking behind my grandparents cabin in S. Lake Tahoe (off of North Upper Truckee).
It was much larger than the other surrounding trees which is why it grabbed my attention
Ponderosa Pines grow to 150-180 feet on average
Ponderosas live to be extremely old, the oldest recorded was 1047 years old!
(Fagan 2009)
8. How do you know its a Ponderosa?
Needles-4-7 Inches long and in groups of 2 or 3
Cones- oval shaped and open with fine prickles
Bark-thick, bright orangey-brown, deeply grooved into jig-saw like flakes
Habitat- dry mountain soils (like Lake Tahoe)
Wernert (1982)
9. History of the Pine
Pine trees have been around since the early Crestaceous period (130 million years ago)
There are records of the Neanderthal man using pine trees for fire
Pines come from a group of gymnosperms (naked seed plants) including four phyla, cycads, ginko, conifers (the pines), and gnetophytes
Conifers range from ground shrubs to redwoods, which are some of the largest trees in the world
Pine trees can be found all over the world, each adapting to the environment in which it lives
The ponderosa lives in dry mountain areas so it has extremely large roots that help it get water and prevent it from blowing over
(Pines: evolution and classification2011; Wernert 1982)
10. Snow Plant(Sarcodessanguinea)
I found this when I was up hiking behind Sorensons off of hwy 89, the trail was still extremely wet from the melting snow and a bunch of these plants were popping up alongside the trail
Snowplants usually bloom in May and June because they flourish as the snow begins to melt (not usually in the snow which is a common misconception from its name)
The thing that first caught my attention was the bright red color of this flower
it is to attract the attention of carrion insects (like beetles) in the deep forest (a perfect of example of adapting to its environment)
(Gauna 2010)
11. More about the Snow plant

  • It belongs to the Monotropaceae, or Indian-pipe family, a family closely related to the Ericaceae, or heath family

12. Because it is a non-photosynthetic plant it has been difficult to completely trace the lineage (though it is thought to stem from the Orobanchaceaeor Cuscutaceae family) 13. The snow plant is related to shrubs like themanzanita, madroo, laurel, and azalea (though not much resemblance ) 14. The snowplant is a monotropoid, which are unusual parasites. 15. The are parasites of fungi, and thrive near other conifers 16. called mycoparasites which is a parasitic fungus whose host is another fungus 17. They dont kill the fungi, they just transfer food and water into its roots(Gauna 2010; Parasitic plants 2010)
18. Near Sawmill Road

  • Off of Sawmill road behind Sawmill pond (near hwy 50) there is a trail that takes you up to some rocks that are fun to climb

19. These rocks are granite, a type of igneous rock that is extremely common in the Lake Tahoe area 20. Granite is a course grained igneous rock, thats white, grey or pink in color 21. The Sierra Nevada is known for its batholiths, or huge masses of granite (and other rock ) that make up many intrusive bodies 22. Like plutons(Monroe 2009; Challoner 2009)
23. A Closer look

  • Granite has crystals that give it a phaneritic or grainy texture; the crystals grew as the liquid magma they were in slowly cooled

24. It is composed mostly of feldspars and quartz 25. These rocks formed within the last 10 million years when there was a lot of volcanic activity taking place 26. The granite formed far below the surface and only after uplift and deep erosion (which took millions of years) did they become what we can see todayMonroe 2009; Challoner2009
27. Echo Lake
Walking the trail alongside Echo Lake I spotted these rocks
Because of their course texture and unique color, these rocks appeared to be Pegmatite, an igneous rock
Pegmatites are usually composed of quartz and potassium feldspar, corresponding very closely with granite
(Monroe; Woolley 2000)
28. Where did they come from
Pegmatites form much like other magmas, with one difference
The water rich magma from which the pegmatite's crystallize inhibit the formation of nuclei
As the minerals in a magma solidify, the remaining magma is more fluid and invades nearby cracks, thus resulting in the mineral rich pegmatite
Pegmatite are often adjacent to large granite plutons (you cant tell from the picture, but there were many other granitic rock in that area)
(Monroe 2009)
29. Sources
Antonucci, David C. (2011). The Natural World of Lake Tahoe. Tahoma CA: David C Antonucci
The Botanical Society of America (2010). Parasitic Plants: SarcodesSanguinea). BSA.Retrieved:
Challoner Jack (2000). Rocks and Minerals: An exploration of gems, crystals, fossils and rocks for the young geologist. New York: ;Lorenz Books
Gauna, Forest Jay (october 2010). Plant of the week: snow plant (sarcodessanguinea). US forest service. Retrieved:
Fagan, Damien (2009). The Ponderosa Pine. Exploring the Southwest. Retrieved:
Net Industries (2011). Pines: Evolution and Classification. Science Rank. Retrieved:
Monroe, James S; Widander Reed (2009). The Changing Earth: Exploring Geology and Evolution (5thed). Belmont: Brooks/Cole CengageLearning
Wernet Susanet al (1982). North American Wildlife: An Illustrated guide to 2,000 plants and animals. New York: Readers Digest