Once, the thought was Mount Mazama blow itself apart in a massive explosion but the lack of evidence did not support this explanation of Crater Lake's born. The alternative theory suggests Mount Mazama just sank into the ground after vomiting all its molten magma insides. Geologists estimate 10 to 12 cubic miles of magma in various forms, such as ash and lava, was expelled by the ancient volcano. This action left only the stump of the former volcano and Crater Lake now fills the void.