Friday, April 6, 2012

Askja Volcano in Iceland Showing Signs of Warming

Several articles and local bloggers have started to chatter about changes at Askja volcano in Iceland, a volcano with a powerful and violent past. In 1875, Askja erupted in one of Iceland's largest historical eruptions, producing a small caldera now filled by Öskjuvatn lake. Askja has erupted during the 20th century (1900's) producing fissures and lava flows outside of the Öskjuvatn lake, but has remained mostly dormant in recent decades.

The volcano is showing signs of increased thermal activity in the caldera, as well as heightened temperatures from fumeroles and springs. It is unclear at this point as to when exactly the warming started, but it appears to have started somewhere between May of 2010, or earlier. There have been some quake swarms and magma intrusion into the volcanic system since the late 1990's, but none of this activity has resulted in an eruption.

Iceland is still in the middle of the cold season, where the Öskjuvatn lake should be frozen over, however it appears that the lake is now liquid, despite the frigid temperatures and snowfall. This suggests a powerful heat source is indeed keeping the lake from freezing. Some speculate that when the ice melts in Iceland, that the volcanoes can erupt more easily, however that is still only a theory and is difficult to prove or demonstrate. Askja warming up in the middle of Winter would seem to suggest that something is happening deep below, as apparently this is not typical for the volcano in the middle of the cold season.


A NASA Image shows an ice free Askja Lake, and an apparent ash layer covering the snow, which could mean a small eruption from a fumerole or vent has already occurred. This picture is from March 23rd.


Blogger Jon Frimann in Iceland has been posting about this for a week or so, as well as some other news outlets that have taken notice.

An eruption at Askja would likely follow the pattern of its 19th-century activity, with fissure swarms and pahoehoe lava flows (it is a shield volcano, much like Mauna Loa or Kilauea in Hawaii). This would not likely produce another caldera forming event, however that is always a possibility, and given that we have no accurate images of the magma chamber below, it is anyone's guess as to what will really occur (but that's the exciting part about volcanoes with long periods of dormancy, you just never know how a new eruption would manifest).

The Smithsonian GVP characterizes Askja as follows:

"Askja is a large basaltic central volcano that forms the Dyngjufjöll massif. It is truncated by three overlapping calderas, the largest of which is 8 km wide and may have been produced primarily from subglacial ring-fracture eruptions rather than by subsidence. A major rhyolitic explosive eruption from Dyngjufjöll about 10,000 years ago was in part associated with the formation of Askja caldera. Many postglacial eruptions also occurred along the ring-fracture. A major explosive eruption on the SE caldera margin in 1875 was one of Iceland's largest during historical time. It resulted in the formation of a smaller 4.5-km-wide caldera, now filled by Öskjuvatn lake, that truncates the rim of the larger central caldera. The 100-km-long Askja fissure swarm, which includes the Sveinagja graben, is also related to the Askja volcanic system, as are several small shield volcanoes such as Kollatadyngja. Twentieth-century eruptions at Askja have produced lava flows from vents located mostly near Öskjuvatn lake."

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