Lunar lava tube Lunar lava tube Lunar lava tubes are sub-surface tunnels on the Moon that are believed to have formed during basaltic lava flows. When the surface of a lava tube cools, it forms a hardened lid that contains the ongoing lava flow beneath the surface in a conduit-shaped passage. Once the flow of lava diminishes, the tunnel may become drained, forming a hollow void. Lunar lava tubes are formed on surfaces that have a slope that ranges in angle from 0.4° to 6.5°. Lunar lava tubes may be as wide as before they become unstable against gravitational collapse. However, stable tubes
Little Lava Lake side of Little Lava Lake and leads south into Three Sisters Wilderness and on to Williamson Mountain. Little Lava Lake Little Lava Lake lies in the Cascade Range about west-southwest of Bend in the U.S. state of Oregon. A close neighbor of Lava Lake, from which it is separated by solidified lava, Little Lava Lake is at an elevation of in the Deschutes National Forest. Generally considered the source of the Deschutes River, 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