Tiny Mediterranean Island was Covered in Searing-Hot Layer of Green Glass After Massive Eruption

Ever hear of an island of glass? A tiny Mediterranean island between Sicily and Tunisia has a remarkable past. Known as Pantelleria, scientists have found that this island was once entirely covered in a searing-hot layer of green glass.

"Today Pantelleria is verdant and has been re-colonized, but even as you approach it by ferry you can see the green layer of glass covering everything-even sea cliffs look like they've been draped in candle wax," said Mike Branney, one of the researchers, in a news release. "Exactly how this happened has only recently come to light."

The island itself is made up of a volcano, which explains how the glass got there in the first place. In order to figure out how the glass covered the entire island, though, the researchers reconstructed how the incandescent density current gradually inundated the entire island after an eruption. They carefully mapped out how the chemistry of the glass varies from place to place, which showed how the ground-hugging current at first was restricted to low, central areas, but then gradually advanced radially toward hills.

"A ground-hugging cloud of intensely hot gases and volcanic dust spread radially out from the erupting volcano in all directions," said Branney in a news release. "In candescent rock fragments suspended in the all-enveloping volcanic cloud were so hot, molten and sticky that they simply fused to the landscape forming a layer of glass, over hills and valleys alike. The hot glass then actually started flowing down all the slopes rather like stick lava. 'Ground zero' in this case was the entire island-nothing would have survived-nature had sterilized and completely enameled the island."

During the study, though, the researchers found something even more interesting. It wasn't just a matter of one, giant eruption. Instead, the devastating current gradually retreated from the hill-tops, and the area covered by it gradually decreased so that by the end of the eruption, only the lower ground was immersed by it. This advance-retreat behavior could actually be typical of catastrophic events in nature, such as other volcanoes.

"We are trying to ascertain whether this volcanic eruption was just a freak, oddball event," said Branney in a news release. "Well it turns out that the delightful island, now used as a quiet getaway by celebrities, has been the site of at least five catastrophic eruptions of similar type. Our investigations should help us understand what happens during similar and much larger explosive eruptions elsewhere around the world, such as the Yellowstone-Snake River region of USA."

The findings are published in the journal Geology.