Ash From Icelandic Eruption May Just Be the Start

Volcano often erupts in tandem with much bigger one nearby

By Alexandra Witze, Science News

The Icelandic volcano that ramped up activity on April 13 could wreak havoc with European air traffic for some time.

Yet the Eyjafjallajökull volcano (pronounced AY-ya-fyat-la-yo-kult) is not the one most researchers have been keeping a wary eye on. Just a few kilometers to the east of the erupting vent is a much bigger and potentially more dangerous volcano called Katla. In the past, when Eyjafjallajökull erupted, Katla did too. So scientists are closely monitoring Katla to see if it, too, might go.

Volcanic activity is par for the course for Iceland, an island that is the above-water manifestation of the Mid-Atlantic Ridge, the seam of mountains running up the center of the Atlantic Ocean like stitches on a baseball. The ridge marks where magma wells up from deep inside Earth, giving birth to new oceanic crust that moves outward from the ridge.

“It’s the place to see seafloor spreading without getting your feet wet,” says Alan Linde, a seismologist at the Carnegie Institution for Science in Washington, D.C., who has placed seismic monitoring equipment on Icelandic volcanoes.

The latest eruption comes on Iceland’s south coast, about 75 miles east of the capital city, Reykjavik. Historical records show that Eyjafjallajökull erupted in 1612 and then again between 1821 and 1823. Some researchers think it also erupted in the year 920.

The current eruption began late in the evening of March 20, when seismic activity around the volcano picked up and then a fissure opened on its side, sending lava fountains spurting into the air. Over the following few weeks the eruption continued at low levels, with a second fissure opening on March 31 and steam and ash plumes occasionally drifting up. By April 12, seismic activity was decreasing; Icelandic authorities lowered the alert level a notch.

But on April 13, a swarm of small earthquakes began and a new vent opened on the south rim of the volcano’s central collapsed chamber, this time directly beneath a glacier. Two days later, the ash plume had grown so large that air traffic in the United Kingdom and much of northern Europe was shut down.

The question now is how activity at Eyjafjallajökull might affect its much larger neighbor. Both volcanoes erupted in 1612 and 1821–23, but Katla has also gone off on its own many times, most recently in 1918. One of the largest eruptions in Iceland’s history, by volume, came in the years 934 to 940 when Katla spewed more than 18 cubic kilometers of lava onto the countryside. The Icelandic Meteorological Office, the Nordic Volcanological Center and other institutions monitor both volcanoes with GPS, seismic and other equipment.

Like Eyjafjallajökull, Katla lies beneath a glacier, and the combination of its larger size and the overlying ice makes it far more dangerous, scientists say. When an erupting volcano melts ice, floods known as jökulhlaups can come pouring out suddenly. Flooding from the Eyjafjallajökull eruption has already caused hundreds of people to evacuate.

Iceland has been devastated by its dozens of volcanoes many times in the past. In the winter of 1783–1784, the eruption of the Laki volcano spewed out enough sulfur dioxide and ash to kill thousands of people across Europe and chill global temperatures the next winter. In the 1960s, a new volcanic island called Surtsey was born off the southwest coast. And in 1973, an eruption on the nearby island of Heimaey threatened to bury a town’s economically important harbor; residents sprayed the advancing lava with seawater to cool it off, and the harbor remained intact.

Aside from outburst floods, ash clouds are the biggest threat from eruptions. In 1989, a KLM flight flew through an ash plume from Alaska’s Mount Redoubt; all four of the aircraft’s engines shut down and the pilot recovered the plane only after it dropped thousands of feet.

On a brighter note, some researchers predict the amount of ash in the atmosphere may be sufficient to cause brilliant red sunsets across Europe.