USGS


Right: Lava cascades plunge 160 feet into Lua Hou Crater, upper part of Mauna Loa's southwest rift zone, during July 1975 eruption. (Photograph by Robin T. Holcomb.) Below: A clockwise-circulating lava lake (nearly 500 feet across) in Pauahi's west pit formed during the same eruption. Bright small spots seen on the lake surface are caused by trees bursting into flame. (Photograph by Robert I. Tilling.) Lua Hou Crater
Circulating lava lake Lava streams that plunge over cliffs or the steep walls of craters form impressive lava cascades or lava falls. Where cascades spill into preexisting craters, lava lakes may be formed. Such lakes are considered inactive and generally form a solid crust within hours or a few days. The still molten lava beneath this crust then takes weeks to years, depending on lake size, to cool and solidify completely. Lava lakes formed at the site of, and sustained by, active eruptive vents are considered active. The crust formed on these lakes is not permanent and breaks up in response to circulation and sloshing of the underlying molten lava. Repeated overflows from active lava lakes raise their level by rampart construction similar to overflowing lava streams. By this process of levee growth, lakes may become perched many feet above their surroundings.

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