Our first United States national park was Crater Lake. Its depth of 592 meters makes it the deepest lake in the US. In around 5700 BC, Mount Mazama collapsed into itself during a tremendous volcanic eruption, losing up to 1,070 metres in height. This period of volcanic activity produced over 150 times as much ash as the 1980 eruption of Mount St. Helens and formed a large caldera that eventually filled and named Crater Lake.