Not by Fire but by Ice


Updated 29 August 06




Thera eruption half again as large as previously supposed
Plus, researchers find active underwater volcanic activity 


28 Aug 06 - The Bronze Age eruption of Thera 3,600 years ago near mainland Greece would have devastated civilizations in the region.

The ash would have plunged an area of at least 300,000 sq km – much of the Mediterranean - into total darkness, say the researchers. Sulphur discharged into the atmosphere would have formed droplets, causing significant cooling of the Earth's surface.

A survey around the island arc of Santorini shows volcanic pumice to a depth of 80m (19 stories!) covering the ocean floor for 20-30km in all directions.

The eruption may have propelled 60 cubic km of magma out of the volcano's crater. (Magma, not ash!)

"It was clear that this was a very substantial eruption to begin with, but this adds 
an exclamation mark," says Steven Carey of the University of Rhode Island , US, a co-author on the study.

The eruption dwarfs even that of Krakatoa, which ejected about 25 cubic km of molten rock, ash and pumice in 1883, killing 40,000 inhabitants of Java and Sumatra in just a few hours. 

Giant waves from the blast would have devastated ports and coastal areas. Tsunami deposits have been found on Crete and the west coast of Turkey .

Some scientists have suggested that the eruption may be connected to the decline of the Minoan people, an ancient sea-faring civilisation living on nearby Crete .

Deep sea vents

The research team also discovered a bed of hydrothermal vents in the crater of nearby Kolumbo, a small submarine volcano located just to the north-east of Thera. The vents are places where water is drawn through seafloor cracks, is superheated and then ejected.

"What this tells us is that Kolumbo has a very active geothermal system beneath it right now," says Carey. "You have to have a lot of heat to drive this kind of vent system."

The study was undertaken by the University of Rhode Island and the Hellenic Center for Marine Research.

(I find it interesting that the date of the Thera eruption coincides with one of the largest eruption of Mount St. Helens, when more than one foot of red-hot  pumice blanketed the Riffe Lake area in Washington state.)

Thanks to icewoman for this link




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