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Eastern Mediterranean

Thera Eruption Was Even Bigger

by Elli Leadbeater, 27 August 2006

The second largest volcanic eruption in human history was much larger than previously thought, according to a report which was issued in 2006.

The Bronze Age eruption of Thera near mainland Greece would have devastated ancient civilisations in the region. Ash would likely have plunged much of the Mediterranean into darkness, and tsunami would have wrecked local ports.

A survey around what is now the island arc of Santorini shows volcanic pumice to a depth of eighty metres covering the ocean floor for about twenty or thirty kilometres in all directions.

A colossal scale

By examining echoes from volcanic deposits on the ocean floor, researchers have shown that the Aegean eruption of Thera shortly after 1500 BC ago may have propelled sixty cubic kilometres of magma out of the volcano's crater.

The new 2006 estimates suggested that the blast was half as large again as had earlier been supposed. The eruption clearly dwarfed even that of Krakatoa, which ejected about twenty-five cubic kilometres of molten rock, ash, and pumice in 1883, killing forty thousand inhabitants of Java and Sumatra in just a few hours.

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

Deadly tidal waves

An eruption of Thera's size would have had drastic implications for people who were living in the region. No bodies have been found in the nearby settlement of Akrotiri, which was buried in ash in a similar way to Roman Pompeii. The city had been evacuated shortly beforehand.

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

During the ash fallout, an area of at least three hundred square kilometres would have been plunged into total darkness, say the researchers. Sulphur which was discharged into the atmosphere would have formed droplets, causing a significant level of cooling of the Earth's surface.

Most scientists accept that the eruption was connected to the decline of the Minoan people, an ancient sea-faring civilisation of nearby Crete. Others have tried to link the event to the legendary disappearance of the island of Atlantis. The blast has been termed 'the single most famous Aegean event before the fall of Troy' (some three hundred years later).

Deep sea vents

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

Map of the Aegean, highlighting the location of Santorini

The location of the island of Santorini is marked on this map of the eastern Mediterranean, with Crete lying just to the south

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

The extreme temperatures and unusual environment of such vents usually attract very specialised forms of life. The vent chimneys are coated in long, tube-shaped bacteria which give them the appearance of 'hairy beasts, like woolly mammoths', reported the lead researcher, Haraldur Sigurdsson.

The study was undertaken by the University of Rhode Island and the Hellenic Center for Marine Research. The largest volcanic eruption in modern times was the Tambora blast on the Indonesian island of Sumbawa in 1815. Scientists calculate it ejected one hundred cubic kilometres of material.



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