The Minoan Catastrophe: The Theran Pyroclastic Surge Theory

Science has long believed that the Minoan Santorini eruption was similar in scale to the Krakatau eruption of 1883 in Indonesia. More recent measurements of Santorini's eruption deposits indicate that it was actually closer to ten times bigger than Krakatau with a VEI (Volcanic Explosivity Index) of seven. This makes Santorini one of the largest volcanic eruptions in the last 20,000 years. Only Tambora in 1815 and a few other eruptions were bigger.

Unlike Tambora, Krakatau and Santorini are marine volcanoes with magma chambers very close to sea level. It is well attested that Krakatau produced a pyroclastic surge containing super-heated steam that traveled over water for 40 kilometers and then rose several hundred meters up the side of Mt. Rajabasa, a 1,284 meter high inactive volcano in southern Sumatra, to burn nearly 2,000 people to their deaths. Johanna Beyerinck, the wife of a Dutch official in Ketimbang, Sumatra was a severely burned eyewitness that narrowly escaped death to give her account. The American trading vessel W. H. Besse was over 80 kilometers from Krakatau when it was blasted by hurricane winds carrying sand and ash, but the bloom’s lethal heat had cooled and the crew survived.

In 1902 the Mount Pelee volcano on Martinique in the Caribbean generated a surge that was calculated to have an initial velocity of over 670 kilometers per hour with a temperature exceeding 1,000°C and killed about 30,000 people. It continued out over open water to capsize and burn ships several kilometers away. Mount Pelee had a VEI of four making it approximately 1,000 times smaller than Santorini. The phenomenon of the pyroclastic surge is well documented in modern times.

The Santorini volcano is part of the Hellenic Volcanic Arc which is caused by the convergence of the African and Eurasian tectonic plates. The Arc is fed magma and dissolved gas (mainly steam - H2O) created by the fractional melting of the African plate as it subducts into the earth’s mantle underneath the Eurasian plate’s Aegean subplate. The rate of subduction is about five centimeters per year. Great quantities of water are transported into the mantle during this process.

The primary gas ejected during eruptions from volcanoes associated with convergent plates is superheated dry steam. If an erupting volcano’s magma chamber is well above sea level, the steam ejected will involve only the water dissolved in the magma and any nearby ground water that is heated by it. This limits the volcano’s ability to generate large steam surges. If the magma chamber is submerged in water and well below sea level, the exposure of the magma to sea water is maximized, but the heat and force of the steam generated is quickly dissipated in the much heavier and colder sea water around it.

In the relatively rare case of a marine volcano (Santorini, Krakatau, etc.) whose magma chamber is at or near sea level, the magma-water exposure is maximized, but the resulting explosions of superheated dry steam are able to enter the atmosphere to scorch everything they touch. The probability of immense high-speed lateral blasts of turbulent hot gas blooms racing over the surface of the surrounding water is greatly increased. Marine volcanoes at sea level are an extreme hazard to all life within reach of their burning pyroclastic surges. Their ability to slide almost frictionlessly at very high velocities over water is probably much greater than what, so far, has been observed or deduced in modern times especially when they are associated with truly colossal eruptions like Minoan Santorini.

Depending on a number of factors, superheated steam can explode from a volcano’s magma chamber like the popping of a shaken soda can’s top. The initial velocity of the gas is proportional to its containment pressure at the time of its jetted release through the explosive opening of one or more vents. I see no reason why the initial velocity of an ejected gas bloom cannot exceed the speed of sound - 344 meters/second (1,238 km/hour). A high-speed pyroclastic gas bloom can travel for a great distance before its killing heat finally dissipates in the atmosphere.

The highly turbulent low-density mixture of superheated dry steam and suspended rock debris with smaller amounts of other gases (carbon dioxide - C02, sulfur dioxide - S02, hydrogen chloride – HCL, etc.) is heavier than the surrounding air and will settle into a layer between the surface of the water and the air above it. Its low-density allows the surge to quickly spread over large areas and easily rise up and crest high topographical features.

Steam occupies a volume that is about 1,600 times the volume of the water that produced it. There were probably many steam surges generated during the Santorini eruption, but an estimate of the minimum size required for a single pyroclastic gas bloom originating from Santorini to completely envelope central and eastern Crete is on the order of 10,000 square kilometers. Assuming an average height of 500 meters for the bloom layer to estimate it’s volume, it would have required only 3.1 cubic kilometers of water (5,000 cubic kilometers of steam) to produce it. It is possible that Santorini’s magma chamber could have exposed more than 30 cubic kilometers of sea water to the molten rock inside it generating over 48,000 cubic kilometers of steam. Given the tremendous scale of the Santorini eruption, it is possible that it could have jetted multiple long-runout pyroclastic steam surges over water to incinerate large areas of Crete and many other islands in the Aegean.

The Neopalatial Minoan Destruction Event

The destruction of Neo-Palatial Minoan Crete has never been definitively explained by science. The evidence indicates that only a thin layer of volcanic ash fell on Crete during the entire eruption sequence. This was probably from a precursory eruption associated with a north wind that preceded the main sequence by some months. Ash from the huge main eruption was blown generally to the east; away from Crete. This was likely due to a west wind in late spring or early summer. The dusting of the crops and plants on Crete would have been cleaned by the wind and rain. The damage from ash fall would have been slight.

The current scientific consensus for the Minoan catastrophe is that huge tsunamis generated by the Bronze Age eruption enveloped Crete and destroyed much of its economy and population. There must have been tsunamis similar to the 35 to 40 meter high waves of Krakatau and they were very likely larger and more devastating. But, even if the biggest of the Theran tsunamis was over 150 meters tall, most of it's worse effects would have been felt on the low-lying coastal plains of the north coast only. Crete's northern coastline would have acted like a 250 kilometer long breakwater that absorbed and reflected much of the tsunami's energy back into the Aegean. This would have significantly reduced the amount of wave energy able to escape into the open waters of the Mediterranean Sea. The damage to Crete's southern coast from a tsunami wrap-around effect would have been minimized.

The vulnerable northern coastal areas of Crete would have been inundated and completely destroyed. The complex at Mallia, about 30 kilometers to the east of Knossos, was scraped almost to its foundation by the tsunamis, but it was only 600 meters from the sea at an elevation of 11 meters. The tsunami would have merely washed up on the nearby 400 to 700 meter high foothills three or four kilometers to the south before it receded back into the sea. No volcanic tsunami could ever have washed completely over mountainous Crete. The large populations of Arkhanes and Phaistos to the south would have been essentially unaffected. The palace complex of Knossos was over five kilometers inland at an elevation of 90 meters and was not scraped clean by a tsunami. It was burned!

Modern evidence shows that populations in areas destroyed by tsunamis and earthquakes recover relatively quickly. Several decades earlier, the Minoans recovered vigorously from a major earthquake event to rebuild their palaces to their greatest extent. The palace at Knossos was repaired and continued to function in some capacity after the catastrophe. But, it was the only palace to be rebuilt. None of the other palaces ever recovered. Apparently, the palace at Phaistos in southern Crete was incinerated by a fierce fire and abandoned forever. The theory of a pyroclastic steam surge(s) scorching and blanketing large areas of Crete in fire during the Minoan eruption is a good fit for the otherwise puzzling archeological evidence.

The Minoan Atlantis Connection

If this theory is validated by the evidence, it would strengthen the already solid archeological connection between the Aegean Minoans of Crete and Thera and Plato’s Atlantis. The pertinent quote from Benjamin Jowett’s translation of Plato’s Timaeus dialogue is:

“But afterwards there occurred violent earthquakes and floods; and in a single day and night of misfortune all your warlike men in a body sank into the earth, and the island of Atlantis in like manner disappeared in the depths of the sea.”

The ringed islands of Thera were utterly destroyed and its inner island, the Minoan’s densely populated international trading hub, had vanished into the sea. When combined with the almost instant holocaust of hundreds of thousands of people falling to their fiery deaths on Crete from the titanic eruption’s pyroclastic surge activity, it paints a scenario that corresponds well with Plato’s description.