T H E S O U T H L A K E TA H O E A R E A

FIELD ASSIGNMENT

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?

• The first thing I learned was that, unlike many of the surrounding Lakes, Lake Tahoe was NOT formed by glaciers• though the glaciers did

have an effect, raising the water level by 800 ft

(Antonucci 2011)

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)

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)

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)

HOW DO YOU KNOW IT’S 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)

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 classification”2011; Wernert 1982)

SNOW PLANT(SARCODES SANGUINEA)

• 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)

MORE ABOUT THE SNOW PLANT

• It belongs to the Monotropaceae, or Indian-pipe family, a family closely related to the Ericaceae, or heath family• Because it is a non-photosynthetic plant it

has been difficult to completely trace the lineage (though it is thought to stem from the  Orobanchaceae or Cuscutaceae family)

• The snow plant is related to shrubs like the manzanita, madroño, laurel, and azalea (though not much resemblance )

• The snowplant is a monotropoid, which are unusual parasites. • The are parasites of fungi, and thrive near

other conifers

• called mycoparasites which is a parasitic fungus whose host is another fungus• They don’t kill the fungi, they just transfer

food and water into its roots (Gauna 2010; “Parasitic plants” 2010)

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

• These rocks are granite, a type of igneous rock that is extremely common in the Lake Tahoe area

• Granite is a course grained igneous rock, that’s white, grey or pink in color

• The Sierra Nevada is known for its batholiths, or huge masses of granite (and other rock ) that make up many intrusive bodies• Like plutons

(Monroe 2009; Challoner 2009)

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• It is composed mostly of

feldspars and quartz

• These rocks formed within the last 10 million years when there was a lot of volcanic activity taking place

• 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 today

Monroe 2009; Challoner 2009

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)

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)

SOURCES

Antonucci, David C. (2011). The Natural World of Lake Tahoe. Tahoma CA: David C Antonucci

The Botanical Society of America (2010). Parasitic Plants: Sarcodes Sanguinea). BSA. Retrieved: http://www.botany.org/parasitic_plants/Sarcodes_sanguinea.php

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 (sarcodes sanguinea). US forest service. Retrieved: http://www.fs.fed.us/wildflowers/plant-of-the-week/sarcodes_sanguinea.shtml

Fagan, Damien (2009). The Ponderosa Pine. Exploring the Southwest. Retrieved: http://www.desertusa.com/mag06/aug/ponderosa.html

Net Industries (2011). Pines: Evolution and Classification. Science Rank. Retrieved: http://science.jrank.org/pages/5234/Pines-Evolution-classification.html

Monroe, James S; Widander Reed (2009). The Changing Earth: Exploring Geology and Evolution (5 th ed). Belmont: Brooks/Cole Cengage Learning

Wernet Susan et al (1982). North American Wildlife: An Illustrated guide to 2,000 plants and animals. New York: Readers Digest