"They're also being subjected to the same tectonic forces. So the chances are that if magma can find a pathway to rise beneath one of them, it can find its way to rise beneath the other."
Researchers do know that the two volcanoes have separate magma chambers, but many suspect that these chambers are physically linked in some way, deep beneath the surface of the Earth.
Overdue eruption
Katla's last eruption was in 1918. It lasted for three weeks and up to a cubic kilometre of material exploded through its vent.
"It's a much more active volcano than Eyjafjallajokull it has had about 20 eruptions in the last 1,000 years, so it erupts about once every 50 years on average," says Professor Gudmundsson.
"At first glance people would say it's now long overdue. But the larger the eruption, the longer the pause (in) time that follows it, and that 1918 eruption was large."
At the moment, there is no seismic activity detectable underneath Katla that would indicate that magma is moving upward underneath it.
Scientists from the Icelandic Meteorological Office are looking at such signals and updating their website regularly with the seismic data that is being produced.
But Dr Goodenough points out that, with Eyjafjallajokull "we only had a few hours warning".
"Seismic monitoring does not necessarily give you advance notice of an eruption." LINKEditor's Note: Please be advised that the above are excerpts from what I consider to be an excellent article and contains the learned opinions of many of our best scientists. It is well worth the time to follow the link and read the entire article. Also, I placed the emphasis on the statement that made it clear that "seismic monitoring does not necessarily give you advance notice of an eruption." As I have pointed out in past articles on earthquakes and volcanoes, most of the time volcanoes do experience seismic activity before an eruption, but not always! My research has demonstrated that approximately ten to fifteen percent of the time volcanoes can erupt with absolutely no warning whatsoever. Please do not be lulled into complacency because there doesn't appear to be any major seismic activity at Katla.
There is not a lot of continuity in the various articles that describe the Katla Volcano except to describe it as enormously dangerous. The BrisbaneTimes.com.au has stated that Katla erupts on a schedule of roughly eighty (80) years; using their figures, Katla is still overdue for an eruption:
Katla, the "witch' volcano, looms over Iceland
The frightening reputation of Katla is mirrored in a savage landscape of black volcanic ridges, blue ice, and snow swept and hardened by powerful winds.
The worry for Icelanders is that each time Eyjafjoell has erupted over the last millennium, Katla, named after an Icelandic witch, quickly followed.
"There have been three Eyjafjoell eruptions and Katla has followed each time," said geophysicist Sigrun Hreinsdottir, at the Earth Sciences Institute. "They are very close."
Some believe the volcanoes are directly linked underground so that magma from one can flow into the other. Hreinsdottir said that what happens inside volcanoes is largely a mystery.
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