Mysterious basalt pillars in Iceland had long been ascribed to a fight between two trolls who had thrown lumps of rock at one another. But scientists have now debunked this local lore, saying the pillars were in fact formed by an unusual geological process.
The pillars, numbering about 40 in all and measuring up to about 8.2 feet tall and 5 feet wide, are dispersed around Skaelingar Valley, where a tributary flows into the Skafta River near Iceland's southern coast. It turns out these formations were not the projectiles thrown by trolls, but were likely the result of unusual lava-water interactions on land.
Looking at the odd collection of pillars, one can imagine how the angry troll explanation may have taken root.
"It's almost an otherworldly experience to see these things for the first time because they're just not very common features," said Tracy Gregg, a volcanologist at the University at Buffalo, in a press release.
Gregg, along with graduate student Kenneth Christle, explain the hollow pillars likely formed around vertical columns of steam and superheated water venting through lava as it flowed over ground.
Gregg said the pillars resemble so-called lava trees in Hawaii, which are hollow basalt cylinders that formed as lava flowed through a forest and cooled when coming in contact with tree trunks. The tree trunks were burned up in the process, leaving the cylinders behind.
"We know that that's not what [the pillars] are in Iceland because when this lava flow erupted, there were no trees in Iceland," Gregg said.
At the Iceland location, Gregg and Christle calculated that the Skafta River Gorge became blocked during the Laki eruption of 1783. This caused the lava that had been flowing through the gorge to back up into smaller tributary valleys like the Skaelingar. As blobs of molten rock pushed up the valley, the ground surface heated up and steam and hot water rising through small gaps between the molten rock formed geysers. Lava then poured past these geysers, quickly cooled and solidified to form the pillars.
Once the jam in the main gorge broke free, the still-molten portion of lava flowed back down the valley, leaving behind the hardened pillars. The whole process likely happened in a matter of just a few hours to a few days. It was also likely a somewhat calm process, Gregg explained, since the pillars were left in tact.
Read more at Discovery News
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