Crater Lake, America's Deepest

Crater Lake in southern Oregon is the deepest lake in the United States at 1,943 feet and the ninth deepest in the world. It was formed roughly 7,700 years ago when a massive volcanic eruption caused Mount Mazama, once a peak as tall as Mount Rainier, to collapse in on itself, creating a caldera that slowly filled with rainwater and snowmelt over centuries. The lake has no rivers flowing into or out of it, and its water is so clear and deep that it reflects a shade of blue so vivid it looks artificial. The Klamath people, who witnessed the original eruption, preserved an oral account of it that has been recognized by geologists as remarkably accurate.

Source: Wikipedia