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Santorini: The Ground is Moving Again in Paradise

“After decades of little activity, a series of earthquakes and deformation began within the Santorini caldera in January of 2011,” said Newman, whose research is published by Geophysical Research Letters. “Since then, our instruments on the northern part of the island have moved laterally between five and nine centimeters. The volcano’s magma chamber is filling, and we are keeping a close eye on its activity.”

Newman, a geophysicist in the School of Earth and Atmospheric Sciences, cannot be certain whether an eruption is imminent since observations of such activity on these types of volcanoes are limited. In fact, similar calderas around the globe have shown comparable activity without erupting. However, Newman says the chamber has expanded by 14 million cubic meters since last January. That means enough magma has been pumped into the chamber to fill a sphere three football fields across.

Should Santorini erupt, Newman says it will likely be comparable to what the island has seen in the last 450 years.

“That could be dangerous,” notes Newman. “If the caldera erupts underwater, it could cause local tsunamis and affect boat traffic, including cruise ships, in the caldera. Earthquakes could damage homes and produce landslides along the cliffs.”

More than 50,000 tourists a day flock to Santorini in the summer months (from May to October). It’s common to see as many as five cruise ships floating above the volcano.

Santorini is the site of one of the largest volcanic events in human history. The Minoan eruption, which occurred around 1650 B.C., buried the major port city of Akrotiri with more than 20 meters of ash and created Santorini’s famous, present-day cliffs. Newman says such history will likely not repeat itself any time soon. Such an eruption comes along once every 100,000 years, and the current inflation in the magma chamber is less than 1 percent of the Minoan blast.

…(Science Daily)

March 23, 2012 Posted by | Seismic, Volcanic | , , , , , , , | Leave a comment

Concerns Grow over Volcanic Eruptions

Scientists have known for decades that hidden under those impressive vistas at sites such as Death Valley and Yellowstone National Park are magma pools that under the right conditions can trigger explosive eruptions.

Now, new research is changing scientists’ understanding of the timing of those eruptions, and prompting them to call for greater monitoring of sites to help save lives when the next big volcano explodes.

Two recent papers highlight the shift. One looked at a Death Valley volcano thought to be 10,000 years old and found it last erupted just 800 years ago, and is still an eruption danger. The other found that large caldera volcanoes, such as the one under Crater Lake in Oregon, can recharge in a matter of decades, rather than the thousands of years previously thought.

“The understanding of the timing of eruptions and the timing of the building up to eruptions is changing,” says Margaret Mangan, the scientist in charge of volcano monitoring in California for the U.S. Geological Survey. “These two papers are very nice examples of good scientific work.”

One thing that’s coming to light is that eruptions are often clustered, with “long stretches of inactivity punctuated by periods of activity that can go on for years,” Mangan says.

The first paper looked at the Ubehebe Crater (you-bee-HE-bee) at the northern end of California’s Death Valley. It’s about half a mile wide and 700 feet deep. It was long believed to have been caused by a volcanic eruption sometime in the past 10,000 years or so.

However, researchers recently looked at beryllium in the rocks and were able to date the last series of eruptions to just 800 years ago. They say the ingredients necessary for another eruption are all still there.

Ubehebe Crater is the result of what’s known as a phreatomagmatic (free-at-oh-mag-MAT-ick) eruption. That means that it has a huge pocket of molten rock, or magma, deep below it. When it begins to push to the surface and comes into contact with water, superhot steam is created, building up pressure until it explodes.

It had been thought that the eruptions would occur only during wet climate periods, and as Death Valley is famously dry now, there was little concern. But using U.S. Geological Survey data, the scientists show that the current water table may be just 500 feet below the surface of the crater.

Caldera volcanoes consist of large underground lakes of magma. As more magma builds up, the pressure builds and the magma starts getting pushed upward through cracks in the Earth’s surface. When the pressure gets too great, it explodes.

Caldera volcanoes typically have a long quiet period prior to eruptions. Writing in Wednesday’s edition of the journal Nature, researchers looked at the eruption of the Santorini volcano in Greece around 1,600 B.C., which released as much as 12 cubic miles of magma.

…(USA Today)

February 3, 2012 Posted by | Volcanic | , , , , , | Leave a comment