September 10, 2012
Greek Island Volcano Ballooning With Magma, Eruptions Not Imminent Researchers Say
Lawrence LeBlond for redOrbit.com - Your Universe Online
New scientific data from the Greek isle of Santorini has shown signs of unrest for the first time in more than 50 years, and could be evidence of an impending eruption similar to the one that last struck in 1950, but far less catastrophic than the one that wiped out Minoan settlements on the island of Crete some 3,600 years ago.The Santorini volcanic eruption circa-1650 BC formed a large crater, or caldera, which is now flooded by the sea. The crater has now begun to fill will molten rock and expand the most since the last eruption from 1939 to 1941.
The chamber of magma beneath the volcano has expanded by 10 million to 20 million cubic meters (comparable to 15 London Olympic Stadiums) between January 2011 and April 2012, according to data compiled by a team of scientists led by Oxford University and published in the journal Nature Geoscience. This expansion is so big that the island has been forced upwards by nearly 6 inches and has triggered a series of small tremors, the first signs of seismic activity in 25 years, raising fears that the volcano is readying to blow once again.
For their research, UK´s Natural Environment Research Council used satellite radar images and Global Positioning System (GPS) receivers that are capable of detecting the movements of the earth´s surface even just minutes of an inch. The data are allowing scientists to get a better understanding about the inner working of the volcano.
A series of small earthquakes began shaking the region beneath the islands of Santorini in January 2011. Most were so small that they were barely detected even with highly-sensitive seismometers in use. Still, it was the first sign of activity beneath the volcano in 25 years.
Study coauthor Michelle Parks, of Oxford University´s Department of Earth Sciences, visited the island several times in 2011 after seismic data began pouring in. She said tour guides had updated her on the changes in the strong scent of gas being released form the summit, and also changes in the color of water in some of the bays around the islands. She said on another occasion “two guides told me they had felt an earthquake while they were on the volcano and that the motion of the ground had actually made them jump.”
“Locals working in restaurants on the main island of Thera became aware of the increase in earthquake activity due to the vibration and clinking of glasses in their bars,” Parks reported residents as saying.
Another coauthor of the paper, Dr. Juliet Biggs of Bristol University, said: “People were obviously aware that something was happening to the volcano, but it wasn't until we saw the changes in the GPS, and the uplift on the radar images that we really knew that molten rock was being injected at such a shallow level beneath the volcano.”
“Many volcanologists study the rocks produced by old eruptions to understand what happened in the past, so it's exciting to use cutting-edge satellite technology to link that to what's going on in the volcanic plumbing system right now,” she added.
The big question is: ℠Will it blow?´
The Oxford team said if the magma estimate is accurate, it is likely Santorini has already filled up half the volume of material known to be belched up during a typical dome-forming eruption. This volcano´s effusive eruptions have been relatively small and frequent, with three occurring in the 20th century alone, the last one in 1950. Santorini is also known to take in rapid breaths of magma before its much more catastrophic eruptions, like the one in BC 1650 that wiped out the Minoan civilization. Fortunately, that type of eruption only occurs once every 10,000 to 30,000 years.
Parks said other good news is that Santorini´s quakes have waned in the past few months, signs that the volcano is calming down.
Alex Morales for Bloomberg reports that some experts believe the events are a sign that a volcanic eruption is on the horizon, but is not imminent. All anomalous tremors, land deformations, chemical releases and heat measurements have subsided, volcanologist Georges Vougioukalakis of the Institute of Geology and Mineral Exploration in Athens, told Morales in an email.
“Now all registered activity is that of the ℠normal´ dormant state of the volcano,” Vougioukalakis, who was not involved on the current research paper, said.
The scientists stressed that the recent activity doesn´t indicate that an eruption is imminent.
The research team used radar data from European Space Agency´s (ESA) ENVISAT satellite from March to December 2011 and the German TerraSAR-X mission from July 2011 to April 2012. GPS systems were used to provide accurate measurements.
Other research on the Santorini volcano was carried out by a Greek team from the Harokopio University in Athens using the same satellite data. Another US-Greek team had similar findings using ground-based GPS instruments.