Long Valley Caldera
The Long Valley Caldera is located in the eastern part of the U.S. state of California to the Nevada border, in Mono County about 25 km south of Mono Lake. She is an active volcanic area, which ( approximately 32 times 17 km east-west and north - south extension ) collapsed because of a violent explosive volcanic eruption 760,000 years ago on an area of 544 km ² and over the existing environment around 300 to 1000 m is sunk. The Long Valley Caldera is one of the largest calderas on earth.
Even today, it is in the area of Long Valley Caldera often to earthquakes and gas leaks. In the west and north of the caldera are the Inyo Craters active, part of the Inyo Mono Craters, which are located in a volcanic related to this. For this reason, the U.S. Geological Survey maintains a private observatory, the Long Valley Observatory ( LVO ) in order to investigate the activity of the caldera, to supervise and to warn the people if there are signs of an imminent eruption.
The caldera forms the upper, northern end of the Owens Valley, between the Sierra Nevada to the west and the White Mountains in the east. In it, the Owens River and its tributary Hot Creek spring. The reservoir Lake Crowley on the Owens River is located entirely in the southern part of the caldera. Land are out in the settlements and at Lake Crowley almost entirely in federal ownership and belong to the Inyo National Forest, a National Forest under the management of the United States Forest Service. In the caldera are the towns of Mammoth Lakes and Crestview. The valley is accessed by U.S. Highway U.S. 395.
Since 1941 Surface water is discharged from the catchment area of the Mono Lakes north of the caldera through the Long Valley Caldera south into the Owens Valley and with the bulk of the water from its watershed in the Los Angeles Aqueduct. He supplies the approximately 450 km distant city of Los Angeles with drinking water.
In the southeast, outside the actual caldera, the Volcanic Tablelands lie. The ground there is tuff, which is developed from volcanic ash that were ejected from the Long Valley Caldera. The landscape with steep to vertical wall structures eroded from these rocks.