The Easter Sierra mountain building has created a long volcanically active area in the east portion of California. Hot Creek begins from the Sierra Nevada Mountain Range as Mammoth Creek, then flows through the Mammoth Lakes and changes its name to Hot Creek Gorge when flowing through Long Valley Caldera. There the water seeps into a series of faults far beneath the surface where geothermal heat the water bring it back to the surface creating travertine fumaroles, hot springs, boiling pots and occasional geysers. The warmth from the water is used upstream at Hot Creek Trout Hatchery used to stock local streams. Regular earthquakes in the area create constant changes to the geothermal activities creating false floors, new boiling pots and geysers. This has has created restrictions on visitors and is now closed after sundown. Fishermen have also introduced invasive New Zealand mud snails which affect native organisms. Hot Creek continues on to connects with the Owens River that terminates at the Owens Sink near Lone Pine, CA, 100 miles south. The unique geology of Hot Creek Gorge has been used in filming the movies of True Grit, North to Alaska, Nevada Smith, and Shoot Out.