Crater Lake, Oregon

Crater Lake is a caldera lake located in Oregon. the lake is the main attraction of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fills a nearly 2,148-foot (655 m) deep caldera that was formed around 7,700 (± 150) years ago by the collapse of the volcano Mount Mazama. On the basis of maximum depth, Crater Lake is the deepest lake in the United States, the second deepest in North America , after Great Slave Lake in Canada, and the ninth deepest lake in the world. 

Due to several unique factors, most prominently that it has no inlets or tributaries, the waters of Crater Lake are some of the purest in terms of the absence of pollutants in North America. The lake has relatively high levels of dissolved salts, total alkalinity, and conductivity. The average pH has generally ranged between 7 and 8.While having no indigenous fish population, the lake was stocked from 1888 to 1941 with a variety of fish. Several species have formed self sustaining populations.

The caldera was created in a massive volcanic eruption that led to the subsidence of Mount Mazama around 5700 BC: about 50 cubic kilometers (12 cubic miles) of rhyodacite was erupted in this event. Since that time, all eruptions on Mazama have been confined to the caldera. Lava eruptions later created a central platform, Wizard Island, Merriam Cone, and other, smaller volcanic features, including a rhyodacite dome that was eventually created atop the central platform. Eventually, the caldera cooled, allowing rain and snow to accumulate and eventually form a lake. Landslides from the caldera rim thereafter formed debris fans and turbidite sediments on the lake bed. It is estimated that about 720 years was required to fill the lake to its present depth of 594 m. Much of this occurred during a period when the prevailing climate was less moist than at present.

The Klamath tribe of Native Americans, who may have witnessed the collapse of Mount Mazama and the formation of Crater Lake, have long regarded the lake as a sacred site. Their legends tell of a battle between the sky god Skell and Llao, the god of the underworld. Mount Mazama was destroyed in the battle, creating Crater Lake. The Klamath people used Crater Lake in vision quests,  which often involved climbing the caldera walls and other dangerous tasks. Those who were successful in such quests were often regarded as having more spiritual powers. The tribe still holds Crater Lake in high regard as a spiritual site.