Their numerous depictions in movies may have led to believe lava lakes are the norm, but it’s actually extremely rare for a volcano to maintain a broiling liquid mass within it’s crater — only a handful of persistent lava lakes exist among the 1,500-or-so active volcanoes around the world.
Scientists from the UK have recently identified what is only the 8th known lava lake — Mount Michael, located in the Subantarctic’s South Sandwich Islands.
Volcanic activity at Mount Michael has been documented for almost 200 years, but the extreme remoteness of the island — along with its challenging physical environment — make field investigations up close a dangerous task.
“The island has been visited on numerous occasions, but no-one has ever climbed the mountain,” geospatial analyst Peter Fretwell from the British Antarctic Survey (BAS) told the BBC.
“If you look at the imagery you can see why: the peak is surrounded by a huge snow-mushroom, extremely soft snow with an icing-sugar-like consistency, probably caused by the continual venting of steam by the volcano.”
“You cannot walk over this,” Fretwell added. “You would have to dig through it, but taking the time to do this on such an active volcano would be dangerous.”
Images taken from space are the only way of looking inside the opening at the summit. Orbiting sensors from as far back as the 1990s have detected heat anomalies in the crater, but it’s taken the most modern satellites to resolve the crater floor, and to verify the presence of the lake.
The information gathered indicates a continuous molten lava feature that is between 90m and 215m wide, holding a consistent temperature of around 1,000C.
But how is Mount Michael able to maintain the lake? Why doesn’t it solidify from time to time?
BAS colleague Dr Alex Burton-Johnson said this had been a puzzle for a long time.
“Our understanding is that volcanoes emit two types of material: rock (in the form of lava, pumice, and volcanic ash) and what we call volatiles (hot gases, including water, carbon dioxide and sulphur dioxide). Hence the white clouds (the water) and the smell (the sulphur),” he told BBC News.
“Both of these are incredibly hot, transferring heat from the depths of the mantle. For most volcanoes, the rock outpourings result in lava flows, but for a lava lake to stay molten but not overflow, the flow of lava from depth must be low, and instead the majority of the expelled matter and the source of the heat must be from the gases.
“This implies that the lava beneath the volcano is very gas-rich.”
The researcher’s findings are reported in Journal of Volcanology and Geothermal Research.
The other seven known Lava lakes are located at Nyiragongo volcano, DR Congo; Erta Ale volcano, Ethiopia; Mount Erebus, Antarctica; Mount Yasur, Vanuatu; Ambrym volcanic island, Vanuatu; Kilauea, Hawaii; and Masaya volcano, Nicaragua.
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[Featured Image: BAS/PETE BUCKTROUT]