Field Assignment Presentation

Evolution of landscapes and life forms in the Lake

Tahoe BasinAnna MasonGEL 103Summer, 2012

Formation of the Lake Tahoe BasinThe Lake Tahoe Basin was created over 2 million years ago by geologic block faulting and volcanism.

Modern Lake Tahoe was shaped and landscaped by scouring glaciers during the Ice Ages, which began a million or more years ago.

Glacier formation and erosion

As a result of the volcanic

activity and faulting, the basin contains a combination of granitic, metamorphic, and volcanic rocks.

Some of the valley bottoms

and lower hill slopes are mantled with glacial moraines, or glacial outwash material derived from the parent rock.

Soils of the basin

Glacial moraine in Angora creek by Meyers.

Igneous rocksIgneous rocks in the Tahoe

Basin were formed from the slow cooling of molten lava that allowed for the crystal formation of the granitic rocks.

The predominant bedrock in the basin is Cretaceous granodiorite of the Sierra Nevada batholith.

(Learning, 2010)

Sierra Nevada Batholith Granite, Meyers

Granitemakes up 70–80% of

Earth’s crust,makes up most of the

Tahoe Basin’s igneous rocks,

large masses of granite are the ingredients of mountain ranges,

it is a plutonic rock, that forms deep underground.

Granite consists of:quartz

feldspar

mica

and dark minerals like biotite and hornblende.

(Granite, 2003)

Basalt

extrusive igneous rock,common type of rock in Earth’s

crust,made of many dark colored

minerals such as pyroxene and olivine,

also contains light colored minerals such as feldspar and quartz,

has very fine grains, individual minerals cannot be seen without magnification.

Nodules of basalt from the Watson Creek and Sawtooth Ridge sources make up a significant component of the beach gravels along Carnelian Bay. (Geology)

Mountain CottontailSylvilagus nuttallii

Family: LeporidaeOrder: LagomorphaClass: Mammalia

The Mountain cottontail is a large size rabbit.

The dorsal pelage is brown to gray, with some black hairs mixed in.

The belly is white and the tail is bicolored.

Young Mountain Cottontail in our backyard in Meyers

HabitatThe mountain

cottontail is found on the east slopes of the Sierra Nevada and the Cascades.

Primarily an animal of rocky, sage-covered hills and canyons.

Range of Mountain Cottontail in California

DietIts diet consist mostly

of grasses and sagebrush, and will eat juniper berries.

usually feeds in the shelter of brush, or in clearings a few meters from cover.

Adult female Cottontail

ReproductionFemales are nearly five

percent larger than males.

The breeding season can extend from February to July.

Four to six young are born after a gestation period of 28-30 days.

Four to five litters can be produced in a season.

(Streubel, 2000)

Baby Cottontail, from the nest in our backyard in Meyers.

OriginsIn Mongolia, a rabbit-like fossil dated 55

million years back was found.

The fossil had long hind limbs and was very close in appearance to modern day rabbits.

Some differences include a long tail and squirrel-like teeth.

This finding suggests that the rabbit family might have existed for about 65 million years or more.

(Earliest)

Gomphos elkema, earliest rabbit relative

Sierra juniper (Juniperus occidentalis ssp. australis)Junipers (Juniperus) belong to the

family Cuppressaceae.

They have scale-like leaves arranged in circles of 3, twigs not forming flat sprays, with berrylike cones less that ½” in length.

The wood is fragrant, usually reddish or reddish-brown, easily worked, very durable, and rarely injured by insects.

Old juniper in Meyers

Juniperus is primarily dispersed by birds.The female cone of the Juniper has been modified to resemble a fruit and provides significant nutritional value to birds.

The foliage and cone-berries of western juniper are important foods for a number of mammals. Mule deer, elk, mountain cottontail, and coyote consume western juniper cone-berries.

Decadent trees provide nesting cavities for mountain chickadees and mountain bluebirds, and hibernation sites for several species of bats.

(McRae, 2009)

OriginsThe serrate-leaf-margin species of North America belong to Clade II (red) of the 6 major clades of all Juniperus species:

Fossil and molecular clock data presented by Mao et al.(2010)indicate that these major clades differentiated from Cupressus about 50-72 million years ago, during the Paleocene.

Disjunctions between Eurasian and North American species arose at three times:

30-43 million years ago during the Eocene-Oligocene transition, when Clade II (red) differentiated;

5-17 million years ago within Clade III (blue),

0.3-4.6 million years ago within the Eurasian and North American varieties of Juniperus communis.

(Mao et al.,2010)

During the past 150 years, western juniper has extended its range and now occupies approximately 42 million acres in the Intermountain West.

It grows over approximately 4 million acres in the Pacific Northwest.

Native range of western juniper

Many native people have used the aromatic foliage and resins for medicinal or spiritual purposes.

An essential oil is obtained by distillation from wood and leaves and used for perfumery, or medicine for its powerful diuretic properties.

(Adams)

Rubber boa (Charina bottae)

non-venomous, small to medium sized snake that may reach about 80 cm.

they vary in color: from olive green, pink, orange, cream or yellow to dark brown, usually with a yellow belly.

rubber boas live in many habitats in California, including moist forest, dry pine forest, and shrubby habitats.

it is hard to spot them during the day because unlike most snakes, rubber boas seem to prefer cool temperatures, and are often active throughout the middle of the night.

 Kingdom

Phylum Class Order Family

ANIMALIA CHORDATA REPTILIA SQUAMATA BOIDAE

I found this young rubber boa crossing Sawmill Road one

late afternoon.

this small constrictor snake has a stout body and smooth shiny small-scaled loose and wrinkled skin which gives the snake a rubbery look and feel. I thought that it was a plastic toy snake on the road when I found it.

the bones of the tail are fused into a solid block that is very strong.

they never bite, but instead curl up into a ball when disturbed; they often hold their blunt tail up, and even make fake "strikes" with it.

rubber boas often eat young rodents, and they probably use the blunt tail to defend ward off the adult rodents. Many snakes have scars on the tail from rodent bites.

a good burrower, climber and swimmer.

often found under logs, boards and other debris, sometimes on roads at dusk.

known to live as long as 40 - 50 years in the wild.

bears 1 - 9 live young from August to November.

(Charina)

Range of the Rubber Boa in California in red

OriginsAniliids, morphologically primitive

among living snakes, feed on relatively heavy, elongate vertebrates. Large aniliids eat larger prey than do small individuals but, as in advanced snakes, they also take small items.

very early snakes used constriction and powerful jaws to feed on elongate, heavy prey. This would have permitted a shift from feeding often on small items to feeding rarely on heavy items, without initially requiring major changes in jaw structure relative to a lizard-like ancestor.

(Greene,1983)

Works cited Adams, R.P. (2010) Juniperus (juniper) Description. N.p. Retrieved from

<http://www.conifers.org/cu/Juniperus.php>.

Charina Bottae (n.d.) Northern Rubber Boa." Charina Bottae. Retrieved from <http://www.californiaherps.com/snakes/pages/c.bottae.html>.

Earliest Rabbit Fossils Found (n.d.) American Museum of Natural History. N.p. Retrieved from <http://www.amnh.org/science/papers/rabbit.php>.

Geology and Soils of the Lake Tahoe Basin. (n.d.) Rep. N.p.: EDAW, n.d. Print. Retrieved from <http://www.placer.ca.gov/Departments/CommunityDevelopment/EnvCoordSvcs/EIR/TVD evProject/~/media/cdr/ECS/EIR/TahoeVista/Ch9GeologySoils.ashx

Granite (2003) World of Earth Science.Encyclopedia.com. Retrieved from http://www.encyclopedia.com/doc/1G2-3437800262.html

Greene, Harry W.(1983). Integrative and Comparative Biology. Dietary Correlates of the Origin and Radiation of Snakes. N.p. retrieved from <http://icb.oxfordjournals.org/content/23/2/431.short>.

Learning Center (n.d.) Lake Tahoe Basin Mgt Unit -. N.p. retrieved from <http://www.fs.usda.gov/detail/ltbmu/learning/?cid=stelprdb5109570>.

Macrae, Ted C. (2009, April 4.)Trees of Lake Tahoe , The Other Conifers. Beetles In The Bush. WordPress. Retrieved from <http://beetlesinthebush.wordpress.com/2009/04/04/trees-of-lake-tahoe-the-other-conifers/>.

Mao Kangshan, Hao Gang, Liu Jianquan, R. P. Adams and R. I. Milne. (2010). Diversification and biogeography of Juniperus (Cupressaceae): variable diversification rates and multiple intercontinental dispersals. New Phytologist 188(1): 254-272.

Streubel, Donald. (2000) Mountain Cottontail. N.p. Retrieved from <http://imnh.isu.edu/digitalatlas/bio/mammal/Lagom/moco/moco.htm>.