 | B&R - Eastern Sierra |
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Large scale block faulting associated with expansion Produces high relief of parallel mountain and valley sequences |
Owens River gorge cut through soft volcanic rock |
Inyo Crater Emissions of carbon dioxide kill trees |
Mammoth Mountain is large volcano on caldera rim.„X Mammoth Mountain area shows evidence of ongoing volcanic activity |
Mammoth Mts Chidago Canyon |
Crater Mtn and lava flows in Owens Valley |
Rainbow Canyon cut into volcanic deposits on the edge of the Darwin Plateau |
Mono Craters |
Volcanic tableland north of Bishop |
Long VallX Thinning of crust produces volcanic activity ey caldera produced by massive eruption about 700,000 years ago |
Black Mts -Faulting and erosion exposes billion year-old rocks in mountains several million years old |
Dark rock in Marble Canyon originally sedimentary but metamorphosed by granite intrusion |
Light colored granite contrasts sharply with layered sedimentary rock nearby |
Papoose Flat Area affected some by Nevadan Orogeny starting around 200 million years ago Western continental margin becomes active as North American drifts west Sierran granites composed of igneous rock that cooled below surface (intrusive) |
Main focus to west but some granite intrusions in Inyo and White Mountains |
Light-colored dolomite in White Mountains |
http://www.geog.ucsb.edu/~joel/g148_f09/lecture_notes/basin_range/basin_range_geol.html
Basin and Range (Trans-Sierra) Geology
Basin and Range Region
Land of high mountains and deep valleys
Bounded on the west by steep eastern face of the Sierra Nevada
Extends east through Nevada to Hurricane Cliffs and Wasatch Front in Utah
Highest and lowest points in lower 48 states 85 miles apart
Highest point is Mt. Whitney at 4,416m (14,480'')
Lowest point in Western Hemisphere is Badwater in Death Valley at -86m (-280'')
2005 with temporary lake
Elevations generally decrease eastward
Mono Lake at 6,700''
Owens Valley floor at 4,000''
Panamint Valley floor at 1,500''
Saline Valley floor at 1,000''
Death Valley floor at sea level
Geologic History
Some of oldest rocks in California exposed on east face of Death Valley
About 1-1.5 billion years old
Match rock in Grand Canyon inner gorge
May have been part of ancient supercontinent Rodinia
Most ranges east of Sierra Nevada composed of 300-700 million year old sedimentary rocks
Rifting splits ancient supercontinent, North America moves eastward
Eastern California was continental shelf off west coast of continent for long period
Passive continental margin comparable to present day Gulf Coast and Florida
Thick layers of carbonate rocks deposited
Derived from corals and other marine organisms
Light-colored dolomite in White Mountains
Area affected some by Nevadan Orogeny starting around 200 million years ago
Western continental margin becomes active as North American drifts west
Overrides oceanic plate which is subducted downward and melts
Collides with various other pieces of crust producing orogenies (mountain building episodes)
Sierran granites composed of igneous rock that cooled below surface (intrusive)
Main focus to west but some granite intrusions in Inyo and White Mountains
Papoose Flat
Light colored granite contrasts sharply with layered sedimentary rock nearby
Dark rock in Marble Canyon originally sedimentary but metamorphosed by granite intrusion
Geologic history of last 25-30 millions years dominated by expansion and thinning of crust
North American plate comes in contact with northwestward moving Pacific Plate
Relative motion becomes tangential, stretching southwestern North American plate
Large scale block faulting associated with expansion
Produces high relief of parallel mountain and valley sequences
Sierra Nevada east to Nevada border
Map
Cross-section
Faulting and erosion exposes billion year-old rocks in mountains several million years old
Thinning of crust produces volcanic activity
Long Valley caldera produced by massive eruption about 700,000 years ago
Volcanic tableland north of Bishop
Owens River gorge cut through soft volcanic rock
Chidago Canyon
Mammoth Mountain is large volcano on caldera rim
Mammoth Mountain area shows evidence of ongoing volcanic activity
Inyo Crater
Emissions of carbon dioxide kill trees, create breathing hazards
Mono Basin also active recently
Mono Craters
Crater Mtn and lava flows in Owens Valley
Rainbow Canyon cut into volcanic deposits on the edge of the Darwin Plateau