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  • 1. Evolution of landscapes and life forms in the Lake Tahoe BasinAnna MasonGEL 103Summer, 2012

2. Formation of the Lake Tahoe Basin The 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 aGlacier formation and erosion million or more years ago. 3. Soils of the basin As a result of the volcanicactivity and faulting, the basincontains a combination ofgranitic, metamorphic, andvolcanic rocks. Some of the valley bottomsand lower hill slopes aremantled with glacialmoraines, or glacial outwashmaterial derived from theGlacial moraine in Angora creek by Meyers.parent rock. 4. Igneous rocks Igneous rocks in the TahoeBasin were formed from theslow cooling of molten lavathat allowed for the crystalformation of the graniticrocks. The predominant bedrock inthe basin is Cretaceousgranodiorite of the SierraSierra Nevada Batholith Granite, MeyersNevada batholith. (Learning, 2010) 5. Granite makes up 7080% ofEarths crust, makes up most of theTahoe Basins igneousrocks, large masses of graniteare the ingredients ofmountain ranges, it is a plutonic rock, thatforms deepunderground. 6. Granite consists of: quartz feldspar mica and dark minerals likebiotite and hornblende. (Granite, 2003) 7. Basalt extrusive igneous rock, common type of rock in Earthscrust, made of many dark coloredminerals such as pyroxene andolivine, also contains light colored mineralssuch as feldspar and quartz, has very fine grains, individualminerals cannot be seen withoutmagnification. 8. Nodules of basalt from the Watson Creek and Sawtooth Ridge sources make up a significant component of the beach gravels along Carnelian Bay. (Geology) 9. Mountain CottontailSylvilagus nuttallii Family: Leporidae Order: Lagomorpha Class: Mammalia The Mountain cottontail is a largeYoung Mountain Cottontail in our backyardsize Meyers The dorsal pelage is brown to gray,with some black hairs mixed in. The belly is white and the tail isbicolored. 10. Habitat The 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 11. Diet Its diet consist mostly ofgrasses and sagebrush, andwill eat juniper berries. usually feeds in the shelterof brush, or in clearings afew meters from cover. Adult female Cottontail 12. Reproduction Females are nearly fivepercent larger thanmales. The breeding season canextend from February toJuly. Four to six young areborn after a gestationperiod of 28-30 days. Four to five litters can beproduced in a season. (Streubel, 2000)Baby Cottontail, from the nest in our backyard in Meyers. 13. Origins In Mongolia, a rabbit-like fossil dated 55million years back was found. The fossil had long hind limbs and was veryclose in appearance to modern day rabbits. Some differences include a long tail andsquirrel-like teeth. This finding suggests that the rabbit familyGomphos elkema,might have existed for about 65 million years earliest rabbit relativeor more.(Earliest) 14. Sierra juniper(Juniperus occidentalis ssp. australis) Junipers (Juniperus) belong to thefamily Cuppressaceae. They have scale-like leavesarranged in circles of 3, twigs notforming flat sprays, with berrylikecones less that in length. The wood is fragrant, usuallyreddish or reddish-brown, easilyworked, very durable, and rarelyinjured by insects. Old juniper in Meyers 15. Juniperus is primarily dispersed bybirds.The female cone of the Juniper hasbeen modified to resemble a fruit andprovides significant nutritional value tobirds. The foliage and cone-berries of westernjuniper are important foods for a numberof mammals. Mule deer, elk, mountaincottontail, and coyote consume westernjuniper cone-berries. Decadent trees provide nesting cavitiesfor mountain chickadees and mountainbluebirds, and hibernation sites forseveral species of bats. (McRae, 2009) 16. OriginsThe serrate-leaf-margin species of North America belong toClade II (red) of the 6 major clades of all Juniperus species: Fossil and molecular clock data presented by Mao etal.(2010)indicate that these major clades differentiatedfrom Cupressus about 50-72 million years ago, during thePaleocene. Disjunctions between Eurasian and North Americanspecies arose at three times: 30-43 million years ago during the Eocene-Oligocenetransition, 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 NorthAmerican varieties of Juniperus communis.(Mao et al.,2010) 17. 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 18. Many native people haveused the aromatic foliage andresins for medicinal orspiritual purposes. An essential oil is obtainedby distillation from wood andleaves and used forperfumery, or medicine forits powerful diureticproperties. (Adams) 19. Rubber boa(Charina bottae) PhylumClass Order Family Kingdom ANIMALIACHORDATAREPTILIASQUAMATABOIDAE non-venomous, small to medium sized snakethat 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 inCalifornia, including moist forest, dry pineforest, and shrubby habitats. it is hard to spot them during the day becauseunlike most snakes, rubber boas seem toprefer cool temperatures, and are often activethroughout the middle of the night. I found this young rubber boa crossing Sawmill Road one lateafternoon. 20. this small constrictor snake has a stout bodyand smooth shiny small-scaled loose andwrinkled skin which gives the snake a rubberylook and feel. I thought that it was a plastictoy snake on the road when I found it. the bones of the tail are fused into a solidblock that is very strong. they never bite, but instead curl up into a ballwhen disturbed; they often hold their blunttail up, and even make fake "strikes" with it. rubber boas often eat young rodents, andthey probably use the blunt tail to defendward off the adult rodents. Many snakes havescars on the tail from rodent bites. 21. a good burrower, climber andswimmer. often found under logs, boards andother debris, sometimes on roads atdusk. known to live as long as 40 - 50 yearsin the wild. bears 1 - 9 live young from August toNovember. (Charina) Range of the Rubber Boa in California in red 22. Origins Aniliids, morphologically primitiveamong living snakes, feed on relativelyheavy, elongate vertebrates. Largeaniliids eat larger prey than do smallindividuals but, as in advanced snakes,they also take small items. very early snakes used constriction andpowerful jaws to feed on elongate,heavy prey. This would have permitteda shift from feeding often on smallitems to feeding rarely on heavy items,without initially requiring majorchanges in jaw structure relative to alizard-like ancestor.(Greene,1983) 23. Works cited Adams, R.P. (2010) Juniperus (juniper) Description. N.p. Retrieved from. Charina Bottae (n.d.) Northern Rubber Boa." Charina Bottae. Retrieved from . Earliest Rabbit Fossils Found (n.d.) American Museum of Natural History. N.p. Retrieved from. Geology and Soils of the Lake Tahoe Basin. (n.d.) Rep. N.p.: EDAW, n.d. Print. Retrieved from . Learning Center (n.d.) Lake Tahoe Basin Mgt Unit -. N.p. retrieved from . Macrae, Ted C. (2009, April 4.)Trees of Lake Tahoe , The Other Conifers. Beetles In The Bush. WordPress. Retrieved from . 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 .