An international team of scientists has found that the second largest volcanic eruption in human history, the massive Bronze Age eruption of Thera in Greece, was much larger and more widespread than previously believed. Scientists from the University of Rhode Island and the Hellenic Center for Marine Research found deposits of volcanic pumice and ash 10 to 80 meters thick extending out 20 to 30 kilometers in all directions from the Greek island of Santorini. "These deposits have changed our thinking about the total volume of erupted material from the Minoan eruption," said URI volcanologist Haraldur Sigurdsson.
     In 1991 Sigurdsson and his URI colleague Steven Carey had estimated that 39 cubic kilometers of magma and rock had erupted from the volcano around 1600 BCE, based on fallout they observed on land. The new evidence of the marine deposits resulted in an upward adjustment in their estimate to about 60 cubic kilometers. An eruption of this size likely had far-reaching impacts on the environment and civilizations in the region. The much-smaller Krakatau eruption of 1883 in Indonesia created a 100-foot-high tsunami that killed 36,000 people.
     The Thera eruption would likely have generated an even larger tsunami and pyroclastic flows that traveled much farther over the surface of the sea. "Given what we know about Krakatau, the effects of the Thera eruption would have been quite dramatic," said Carey, a co-leader of this year's expeditions. "The area affected would have been very widespread, with much greater impacts on the people living there than we had considered before."
     Thera has erupted numerous times over the last 400,000 years, four of which were of such magnitude that the island collapsed and craters were formed. Some scientists believe the massive eruption 3,600 years ago was responsible for the disappearance of the Minoan culture on nearby Crete.
     The study was part of a longer research led by National Geographic Explorer-in-Residence Robert Ballard, a URI oceanography professor and president of the Institute for Exploration, which included a search for Bronze Age shipwrecks in the Black Sea and a survey of the seafloor in the Sea of Crete.
     Additional details can be found at www.uri.edu/endeavor/thera or www.oceanexplorer.noaa.gov/explorations/06blacksea/.

Source: University of Rhode Island News Bureau (23 August 2006)