Lava Beds National Monument Stronghold, which is 450,000 years old. Petroglyph Point was created about 275,000 years ago when cinders erupted through the shallow water of Tule Lake; violent explosions of ash and steam formed layers upon layers of tuff. The caldera is thought to have formed by subsidence, during which basalt and andesite were erupted up on the slopes. Lava flows dated to about 30,000–40,000 years ago formed most of the lava tube caves in the monument. As the hot basaltic lava flowed downhill, the top cooled and crusted over, insulating the rest of the lava and forming lava tubes. Lavacicles on the
Lava Lake (Oregon) Lava Lake (Oregon) Lava Lake lies in the Cascade Range about west-southwest of Bend in the U.S. state of Oregon. It is a close neighbor of Little Lava Lake, from which it is separated by solidified lava. Lava Lake is at an elevation of in the Deschutes National Forest. The lake covers to an average depth of . Lava Lake, Little Lava Lake, and other nearby lakes formed after lava flows from Mount Bachelor altered drainage patterns in the area. Solidified lava flows are visible along the shorelines of both lakes, and the volcanic peaks Broken Top and South Sister