You can't blame those pesky angry trolls -- at least not this time, according to an article in Earth Magazine.
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," Tracy Gregg, a volcanologist at the University at Buffalo, told Earth Magazine.
Gregg, along with graduate student Kenneth Christle, explained that 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 trunks were burned up in the process, leaving the cylinders behind. Gregg explained to the magazine that they know this didn't happen in the Iceland location since there were no trees there.
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 rising through small gaps between the molten rock formed geysers. Lava then poured past these geysers, 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 few hours to a few days. It was also likely a somewhat calm process, Gregg explained, since the pillars were left intact.
"Normally, when we think of lava coming in contact with water, we think of that water flashing to steam and causing an explosion," Gregg told Earth Magazine. "Here's an example where … you could've stood right there and watched it."
The explanation may not be as intriguing as a troll fight, but it was published in the Journal of Volcanology and Geothermal Research.
-- via Earth magazine.