Читать книгу Top Trails: Lake Tahoe. Must-Do Hikes for Everyone онлайн

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Geologists speculate that the landform that would ultimately become the Tahoe Basin we know today was once beneath a shallow ancient sea in the supercontinent of Pangaea. The North American Continental Plate eventually broke away from Pangaea and headed west, colliding into the Pacific Ocean Plate, which was drifting east. Extreme pressure and heat were created as the North American Plate rose above the Pacific Plate, producing molten rock that slowly solidified beneath the sedimentary surface into granitic rocks, which were later exposed through faulting.

Faulting fractures in the earth’s crust allowed blocks of land to rise and fall, pushing the primarily plutonic rocks of the Sierra Nevada up from the ancient seabed. Two principal faults evolved in the Tahoe area, which produced uplifts that became the main Sierra Crest to the west and the Carson Range to the east. In between, the down-thrown fault block formed the deep V-shaped valley of the Tahoe Basin.

A lake began to form at the lowest, southern end of the basin, fed by precipitation and creeks draining the surrounding mountains. The level of the lake rose steadily, until an outlet for the river draining the lake was reached to the north, near the current town of Truckee. Later, a significant lava flow from Mount Pluto, site of the Northstar California Resort, dammed the outlet and caused the lake to rise again. Eventually the river was able to cut a new outlet through the volcanic rock, near the present-day Tahoe City. The highest level Lake Tahoe ever reached was an estimated 600 to 800 feet above the current level. Additional volcanic activity occurred at both the south end of the basin, around Carson Pass, and the north end of the basin, near Donner Pass.