A lava lake on Kilauea, Hawaii exploded into life last week, after part of the crater wall collapsed inwards. Although no-one was injured, the resulting pyrotechnics were certainly worth a look, as reported by National Geographic.
Lava lakes are one of the most dramatic features of a volcano. They require a certain set of conditions to operate: magma that is not too gloopy or too fluid, and just the right amount of lava being forced to the surface. These broiling, bubbling masses are normally self-sustaining, in that their volume is roughly constant over time. Occasionally, an increase in lava production does cause them to spill over in dramatic, and sometimes dangerous, lava curtains.
Only five active lava lake systems exist in the world, one of which is in Kilauea. This is actually divided into two separate lakes: one in the Halema’uma’u crater, and one in the Pu’u O’o crater. A rockfall on the east rim of the former appears to have triggered a small explosion within the lava lake, creating some spectacular fireworks for any passersby to see. The extreme heat and acidity of the lava lakes slowly eroded the crater wall rocks over time, causing them to eventually collapse and tumble into the fiery pit.
Normally, lava lakes display a constantly circulating, chaotic state, wherein cooled lava at the surface solidifies, becomes denser, and sinks back into the lake, causing it to melt. Suddenly piercing the crusty surface of a lava lake destabilizes it, forcing air into it. This briefly cools part of it, depressurizing its contents. Among other things, this causes a sudden production of bubbles, which explosively burst as they force their way to the surface.
This is precisely what happened when rocks tumbled into one of Hawaii’s two lava lakes last Friday. The resulting explosion propelled lava up to 110 meters (360 feet) into the air. Although the United States Geological Survey notes that these molten ballistics can prove hazardous to nearby humans, no-one was injured in the latest paroxysm.