Santorini  Volcano

Geological History: the volcano of Thera      For decades, scholars have debated whether the eruption  of the Thera volcano in the Aegean more than 3,500 years ago,  brought about the mysterious collapse of Minoan civilization  at the peak of its glory… The volcanic isle (whose remnants are known as Santorini)  lay just 110km from Minoan Crete, so it seemed quite reasonable,  that its fury could have accounted for the fall of the Minoan civilisation…. This idea suffered a blow in 1987 when Danish scientists studying cores  from the Greenland icecap reported evidence that Thera exploded  in 1645 BC, some 150 years before the usual date… That put so much time between the natural disaster and the Minoan  decline, that the linkage came to be widely doubted,  seeming far-fetched at best. Now, scientists at Columbia University, the University of Hawaii  and other institutions are renewing the proposed connection… New findings, they say, show that Thera's upheaval was far more violent than previously calculated -- many times larger  than the 1883 Krakatoa eruption,  which killed more than 36,000 people.  They say the Thera blast's cultural repercussions were equally large,  rippling across the eastern Mediterranean for decades,  even centuries… “ It had to have had a huge impact," said Floyd W. McCoy,  a University of Hawaii geologist who has studied the eruption  for decades and recently proposed that it was much more violent  than previously thought… The scientists say Thera's outburst produced deadly waves  and dense clouds of volcanic ash over a vast region,  crippling ancient cities and fleets, setting off climate changes,  ruining crops and sowing wide political unrest. For Minoan Crete, the scientists see direct and indirect  consequences.  McCoy discovered that towering waves from the eruption  that hit Crete were up to 15m high, smashing ports  and fleets and severely damaging the maritime economy. Other scientists found indirect, long-term damage.  Ash and global cooling from the volcanic pall caused wide crop failures  in the eastern Mediterranean, they said,  and the agricultural woes in turn , set off political upheavals  that undid Minoan friends and trade… "Imagine island states without links to the outside world, " William B. F. Ryan, a geologist at Columbia's Lamont-Doherty Earth Observatory, told a meeting of the American Geophysical Union.   Compelling evidence  Scientists who link Thera to the Minoan decline say  the evidence is still emerging and in some cases sketchy.  Even so, they say it is already compelling enough to have convinced many archaeologists, geologists and historians that the repercussions probably amounted to a death blow for Minoan Crete. In 1939, Spyridon Marinatos proposed that the eruption wrecked Minoan culture on Thera and Crete.  He envisioned the damage  as done by associated earthquakes and tsunamis… While geologists found tsunamis credible,  they doubted the destructive power of Thera's earthquakes,  saying volcanic ones tend to be relatively mild.  The debate simmered for decades. In the mid-1960s, scientists dredging up ooze  from the bottom of the Mediterranean began to notice  a thick layer of ash that they linked to Thera's eruption.  They tracked it over thousands of square miles. Such clues helped geologists estimate the amount of material Thera  spewed into the sky and the height of its eruption cloud,  main factors in the Volcanic Explosively Index.  Its scale goes from zero to eight and is logarithmic,  so each unit represents a tenfold increase in explosive power.  Thera was given a VEI of 6.0, on a par with Krakatoa in 1883. The similarity to Krakatoa, which lies between Sumatra and Java,  helped experts better envision Thera's wrath. Krakatoa hurled rock  and ash more than 35km high and its blasts could be heard  4,800km away. Its giant waves killed thousands of people.  Despite the power of Thera, the Danish scientists' evidence raised doubts about its links to the Minoan decline. Another blow landed in 1989 when scholars on Crete found,  above a Thera ash layer, a house that had been substantially  rebuilt in the Minoan style.  It suggested at least partial cultural survival.  By 1996, experts like Jeremy B. Rutter, head of classics  at Dartmouth College, judged the chronological gap too extreme  for any linkage. "No direct correlation can be established" between the volcano and the Minoan decline, he concluded. As doubts rose about this linkage, scientists found more evidence  suggesting that Thera's eruption had been unusually violent  and disruptive over wide areas. Scientific maps drawn in the 1960s  and 1970s showed its ash as falling mostly over nearby waters  and Aegean islands. By the 1990's, however, the affected areas had been found  to include lands of the eastern Mediterranean from Anatolia to Egypt. Scientists found ash from Thera at the bottom of the Black Sea  and Nile delta.  Massive anomaly  Peter I. Kuniholm, an expert at Cornell University on using tree rings  to establish dates, found ancient trees in a burial mound in Anatolia,  what now is in the Asian part of Turkey. For half a decade those  trees had grown three times as fast as normal, apparently because Thera's volcanic pall turned hot, dry summers into seasons  that were unusually cool and wet. "We've got an anomaly, the biggest in the past 9,000 years",  Kuniholm said in an interview. Two years ago McCoy  stumbled on more evidence suggesting that Thera's ash fall,  had been unusually wide and heavy. During a field trip to Anafi,  an island some 32km east of Thera, he found to his delight  that the authorities had just cut fresh roads that exposed layers  of Thera ash up to 3m thick a surprising amount that distance  from the eruption. Greek colleagues showed him new seabed samples  taken off the Greek mainland, suggesting that more ash blew westward  than scientists had realized. Factoring in such evidence, McCoy calculated that Thera  had a VEI of 7.0 -- what geologists call colossal and exceedingly rare. In the past 10,000 years only one other volcano has exploded  with that kind of gargantuan violence: Tambora, in Indonesia,  in 1816, it produced an ash cloud in the upper atmosphere that reflected sunlight back into space and produced a year without  a summer. The cold led to ruinous harvests, hunger and even famine  in the US, Europe and Russia. » I presented this evidence last summer  at a meeting," McCoy recalled, "and the comment from  the other volcanologists was, `Hey, it was probably  larger than Tambora… Some prominent archaeologists have concluded that the volcano's  long-term repercussions meant the end of Minoan Crete… They argue that the revolt of nature over the predictable certainties  of Minoan religion probably crippled the authority of the priestly ruling  class, weakening its hold on society…