Mon Mar 22, 2:15 pm ET
REYKJAVIK (AFP) - A small volcano eruption that forced more than 600 people to flee their homes in Iceland over the weekend could conceivably set off a larger volcano, experts warned Monday.
"Historically, we know of three eruptions in (the large volcano) Katla linked to eruptions in Eyjafjallajokull," Magnus Tumi Gudmundsson, a professor of geophysics and civil protection advisor, told AFP, adding however that there so far was no indication of volcanic activity at Katla.
A volcanic eruption near the Eyjafjallajokull glacier in southern Iceland forced hundreds to flee their homes early Sunday, but no casualties were reported.
It was the first volcanic eruption in Iceland since 2004, and the first in the vicinity of the Eyjafjallajokull glacier since 1823.
Icelandic authorities warned Monday of increased disturbance in the area.
"Police have increased surveillance in the whole area around the Eyjafjallajokull and Myrdalsjokull glaciers because of increased disturbance this morning in the volcanic eruption," the police and civil protection department said in a statement.
Police also warned there could still be danger in travelling or driving in the vicinity of the volcanic area and closed some of the area's roads.
Public broadcaster RUV reported small earthquakes in the region of the volcanic eruption were measured early Monday, and said the 800 metre (yard) fissure caused by the eruption was getting larger.
Gudmundsson however said that while the lavafield from the fissure had grown, "the fissure itself has not grown or enlarged."
He also said the threat of the fissure heading towards the Myrdalsjokull glacier, which sits on top of Katla had diminished.
Katla, which is considered one of the most dangerous volcanos in Iceland, last erupted in 1918.
"An evacuation plan exists if Katla goes off but now we are just taking it day by day and refocussing on the Eyjafjallajokull evacuation plan and what is going on there," local police chief Kjartan Thorkelsson told AFP.
Historically, Katla has erupted within a year of an eruption at Eyjafjallajokull, but Gudmundsson tried Monday to downplay the danger.
"Katla is extremely well-monitored by GPS earthquake monitoring devices and there is nothing to indicate that something is going on in Katla," he insisted.
Blasts of lava and ash shot out of a volcano in southern Iceland on Monday and small tremors rocked the ground, a surge in activity that raised fears of a larger explosion at the nearby Katla volcano.
Scientists say history has proven that when the Eyjafjallajokull volcano erupts, Katla follows - the only question is how soon. And Katla, located under the massive Myrdalsjokull icecap, threatens disastrous flooding and explosive blasts when it blows.
Saturday's eruption at Eyjafjallajokull (AYA-feeyapla-yurkul) - dormant for nearly 200 years - forced at least 500 people to evacuate. Most have returned to their homes, but authorities were waiting for scientific assessments to determine whether they were safe to stay. Residents of 14 farms nearest to the eruption site were told to stay away.
Several small tremors were felt early Monday, followed by spurts of lava and steam rocketing into the air.
Iceland sits on a large volcanic hot spot in the Atlantic's mid-oceanic ridge. Eruptions, common throughout Iceland's history, are often triggered by seismic activity when the Earth's plates move and when magma from deep underground pushes its way to the surface.
Like earthquakes, predicting the timing of volcanic eruptions is an imprecise science. An eruption at the Katla volcano could be disastrous, however - both for Iceland and other nations.
Iceland's Laki volcano erupted in 1783, freeing gases that turned into smog. The smog floated across the Jet Stream, changing weather patterns. Many died from gas poisoning in the British Isles. Crop production fell in western Europe. Famine spread. Some even linked the eruption, which helped fuel famine, to the French Revolution. Painters in the 18th century illustrated fiery sunsets in their works.
The winter of 1784 was also one of the longest and coldest on record in North America. New England reported a record stretch of below-zero temperatures and New Jersey reported record snow accumulation. The Mississippi River also reportedly froze in New Orleans.
"These are Hollywood-sort of scenarios but possible," said Colin Macpherson, a geologist with the University of Durham. "As the melt rises, it's a little like taking a cork out of a champagne bottle."
There are three main places where volcanoes normally occur - along strike-slip faults such as California's San Andreas fault line, along areas where plates overlap one another such as in the Philippines and the Pacific Rim, and in areas like Iceland, where two of the Earth's plates are moving apart from each other in a so-called spreading system.
Unlike the powerful volcanos along the Pacific Rim where the slow rise of magma gives scientists early seismic warnings that an eruption is imminent, Iceland's volcanos are unique in that many erupt under ice sheets with little warning.
Magnus Tumi Gudmundsson, a geologist at the University of Iceland who flew over the site Monday, said the beginning of Saturday's eruption was so indistinct that it initially went undetected by geological instruments. Many of the tremors were below magnitude 2.6.
Using thermal cameras and radar to map the lava flow, Gudmundsson and other scientists were able to determine that the lava from Eyjafjallajokull was flowing down a gorge and not moving toward the ice caps - reducing any threat of floods.
He said he and other scientists were watching Katla but Monday's trip was meant to assess immediate risk.
"A general expectation is that because of the Eyjafjallajokull eruption, the fissure would widen and in that sense, there's a greater risk of extending into or underneath the glaciers and prompting an eruption at Katla," said Andy Russell with Newcastle University's Earth Surface Processes Research Group, who went with a team to Iceland before the eruption. "From records, we know that every time Eyjafjallajokull erupts, Katla has also erupted."
Russell said past Katla eruptions have caused floods the size of the Amazon and sent boulders as big as houses tumbling down valleys and roads. The last major eruption took place in 1918. Floods followed in as little as an hour.
Those eruptions have posed risks to residents nearby, but most of Iceland's current population of 320,000 live in the capital of Reykjavik on the western part of the island.
Southern Iceland is sparely populated but has both glaciers and unstable volcanoes - a destructive combination.
The last time there was an eruption near the 100-square-mile (160 square-kilometer) Eyjafjallajokull glacier was in 1821, and that was a "lazy" eruption that lasted slowly and continuously for two years.
Iceland is one of the few places in the world where a mid-ocean ridge actually rises above sea level. Many volcanic eruptions along the ocean basin often go undetected because they can't be easily seen.
First settled by Vikings in the 9th century, Iceland is known as the land of fire and ice because of its volcanos and glaciers. During the Middle Ages, Icelanders called the Hekla volcano, the country's most active, the "Gateway to Hell," believing that souls were dragged into the fire below.
The last major volcanic eruption in Iceland occurred in 2004 with the Grimsvotn volcano.
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