Beneath these tranquil blue waters is a story of fire and cataclysm. The western hemisphere’s deepest lake was once a 12,000-foot (3,700 m) peak called Mount Mazama. The mountain towered over the forested landscape of central Oregon, its cone-shape summit hidden beneath snow, ice and clouds. But all that changed some 7,700 years ago when the top of the mountain exploded in a column of dark smoke and steam. The snow and ice packs at the summit immediately melted, gathering up ash and sediment as water and gases poured down the slopes in super-heated mud avalanches called pyroclastic flows. As the eruption continued, the top of Mount Mazama collapsed in on itself, reducing the height of the mountain by more than a mile (1.6 km). Eventually the volcano grew quiet and the empty caldera slowly began to fill with water, creating the spectacular Crater Lake we see today.