Lava pillars on land
A 2013 study has concluded that bizarre, hollow spires in Iceland are a unique type of volcanic formation that was previously only known to form in the deep ocean.
University at Buffalo geologist Tracy Gregg was hiking with her husband in the Skaelinger Valley in 1998 in Iceland when she noticed the knobby, hollow spires dotting the landscape.
Though her guide and others told her the rocks were the detritus of warring trolls who had tossed them through the landscape, Gregg was unconvinced.
The formations looked very similar to those she studied in her research: lava pillars that form at mid-ocean ridges.
At places where the continental plates are pulling apart under the ocean, columns of hot water seep through the pillowy lava on the ocean floor. That process cools the lava surrounding the water columns, forming hardened, hollow pillars when the lava ebbs. The Icelandic spires, with their hollow interiors, seemed to have been formed in a very similar process.
Unfortunately, Gregg didn't have a chance to take a second look at these pillars until 2010, when her graduate student Kenneth Christie received a grant to travel to Iceland to inspect the pillars more closely.
The team concluded that the pillars formed just as they would have in the ocean, with hollow interiors encircled by lava walls. The findings change geologists' understandings of the types of interactions that are possible when lava meets water.
Some of the pillars have a glassy texture, characteristic of the interaction between lava and water. The lava cooled fast enough to drip, but not fast enough to form crystals.
Steam or pillow
Previously, geologists believed that when water and lava met on land, the water either drowned the lava, forming pillowy structures, or the lava heated the water in a flash to form steam, which then exploded.