Crater Lake
Mount Mazama is part of the Cascade Range island arc.  It was built up over a period of at least 400,000 years. The caldera was created in a massive volcanic eruption. That led to the lowering of Mount Mazama around 5700 BC. Since that time, all eruptions on Mazama are limited to the caldera.  Lava eruptions later created a central platform, called Wizard Island. Sediments and material from landslides also covered the caldera floor.