Crater Lake National Park's Caldera is an 8 x 10 kilomter natural body of water, formed by the volcanic eruption of Mount Mazama. The highest point, Hillman Peak stretches over 2,485 meters tall! At 592 meters deep, it is the largest Lake in the United States, and the 9th deepest in the world! The average temperature at below 90 meters deep is 3 degrees Celsius, yet seldom does this glorified lake ever freeze because the weather systems usually originate from the Pacific Ocean. In its prolonged history, there was only a complete surface freeze in 1949, however in 1985, there was a 95% surface freeze! Fishing is encouraged at Crater Lake because all fishes are invasive species, or not native to these waters. In fact, fishing licenses aren't required and there is no limit on how many fish you catch! Formed by the volcanic eruption, there were no fish whatsoever at Crater Lake until the 1940's, when 6 different species were introduced. Out of the 6 species, only the Rainbow trout and Kokanee Salmon have continued to survive today. The caldera is a riveting book which tells the story of the aftermath from Mount Mazama's explosion.