Wizard Island cinder cone, with a symmetrical 90-m-wide crater at its summit, formed above the west floor of Oregon's Crater Lake caldera within a few hundred years of caldera formation. A lava flow created the peninsula in the foreground on the NW side of the cone, which forms a small island on the west side of Crater Lake. A submerged dome, 30 m beneath the surface 1 km east of Wizard Island, is the youngest feature of Crater Lake caldera.
The spectacular 8 x 10 km wide Crater Lake caldera was formed about 6850 years ago when Mount Mazama, a complex of overlapping shield volcanoes and stratovolcanoes, collapsed following a major explosive eruption. The eruption blanketed a huge area with ash falls and produced pyroclastic flows that swept all sides of the volcano. The caldera, seen here from its southern rim, is 1200 m deep and filled to half its depth by the intensely blue waters of Crater Lake.