Crater Lake is a caldera lake in the western United States, located in south-central Oregon. It is the main feature 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[1] that was formed around 7,700 (± 150) years ago[2] by the collapse of the volcano Mount Mazama. There are no rivers flowing into or out of the lake; the evaporation is compensated for by rain and snowfall at a rate such that the total amount of water is replaced every 250 years. At 1,943 feet (592 m), the lake is the deepest in the United States, and the seventh[3] or ninth deepest in the world, depending on whether average or maximum depth is measured.