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Roger Weller, geology instructor
by Mark Nobles
When the World Ended
The Bronze Age Eruption of Thera
Three and a half thousand years ago a volcanic eruption ripped through the sun washed world of the Aegean with a ferocity surpassed rarely in all of recorded history. The eastern half of the Mediterranean Sea was blanketed with fallout and the climate of the entire planet changed; the effects were felt around the world. Tsunamis smashed coastal towns along the entire width and breadth of the Mediterranean Sea. This disaster was so profound that it gave rise to one of the most enduring legends of human history: The lost city of Atlantis. Many details of this cataclysm are forever lost to antiquity, but by comparing the geological and archaeological remains of the eruption of Thera, now known as Santorini, with observed and documented volcanic eruptions of more recent years, a surprisingly accurate recreation of the events can be presented.
Thera and the Minoans
The island of Thera, renamed Santorini in the early 17th century, is found at the southern end of the Cyclades Island chain, roughly seventy miles north of Crete. Typical of the Mediterranean, Thera enjoys a mild climate with warm, bright summers and comfortably cool winters, ideal for crops of olives, grapes and tomatoes. Until 1840, the principal exports were sweet wines, which were popular throughout Europe for centuries. Today, the islanders enjoy a lucrative tourist industry.
Artwork courtesy of Greeka.com
It is suggested that at the time of the Minoan colonization of Thera, the summit stood over a thousand feet above sea level, with some estimates placing it at three times that height.
The idyllic conditions often mask the fact that this island is actually a
massive shield volcano, built up over hundreds of millions of years, constructed
of layer upon layer of lava flows. Evidence of this can be seen in contemporary
photographs of the caldera which display different layers of basalt and tephra.
Current research identifies a dozen separate eruptions over the last one million
courtesy of Brent Weller
During the Bronze Age Thera was home to a heavily populated Minoan
colony, similar to many such colonies scattered across the islands of the Aegean
Sea. The Minoans were wealthy merchantmen, skilled sailors and talented
engineers with well established trade routes that extended from Egypt to Sicily.
courtesy of Michael Lahanas
For centuries, they brought trade goods and luxuries from one end of
the Mediterranean world to the other and by doing so, had built for themselves a
rich and prosperous culture. Like all Minoans, the Therans were a peaceful
people with a great admiration and appreciation for the arts. There are many
frescos found inside the remains of Theran homes that display a love of the
natural world. Scenes of marine and animal life depict amazingly lifelike images
from points as far away as Ethiopia.
Photos courtesy of Susan and Tony Wright
The contrasts to this paradise are the recurring earthquakes. Most
occur deep beneath the sea and are hardly noticed, although the more violent
quakes have often caused damage across the island. Evidence of this was
discovered in the ruins of Akrotiri, a Bronze Age city on the southern coast of
the island. Remains of damaged buildings, forever frozen in time, are perfectly
preserved by a layer of tephra that blankets the island to a depth of 160 feet.
Archaeologists have determined that some of these buildings were undergoing
repairs at the time of the cataclysmic eruption, and piles of rubble indicate
that some structures were being deliberately dismantled and rebuilt. It seems
that the Minoans were no strangers to seismic activity.
Photo courtesy of Tom Pfeiffer / ww.volcanodiscovery.com
Buried under sixteen stories of tephra from the Minoan Eruption is a separate, much thinner layer. This precursory layer of ash and debris shows signs of erosion, most likely from the winter rains. This evidence, coupled with the damaged buildings, might indicate that Thera had suffered from a large earthquake and a minor volcanic eruption only a few months, or even weeks before the devastation that destroyed the island.
It is interesting to note that no human remains have been found in any of the archaeological sites on Santorini. This would seem to indicate that the Minoans were able to correctly interpret any warning signs of impending disaster and evacuate their island in time.
The Tectonics of the Aegean
To truly understand the causes of such a devastating eruption, one
must first look briefly at where this volcano is located, and the tectonic
movement of the earthís crust in this portion of the world. Thera and the
Cyclades Islands are part of the geologic formation known as the Aegean
micro-plate, a segment of the sea floor that is continually forced down into the
earthís mantle through tectonic subduction by the combined movements of the
surrounding African and Anatolian tectonic plates, and a stationary Europe.
Artwork courtesy of Bryn Mawr College
For hundreds of millions of years the Aegean micro-plate has been smashed, crushed and ground under the surrounding continental plates, resulting in a region rife with seismic and volcanic activity. The tremendous pressures generated by such continental activity made disaster for the Minoans inevitable.
Thera exploded violently with a comparable force of over 600
megatons, its shock waves damaging buildings more than sixty miles away. The
sound of the blast was heard in Greece, Turkey, Palestine, Egypt, and as far
away as Spain. There were no lava flows, but in a classically Plinian eruption
smoke, ash and debris were ejected in a vertical column rocketing nearly
twenty-two miles high. Cooling rapidly in the upper stratosphere, some of the
lighter material was carried away by the strong, high altitude winds. This
continued for several days, as fourteen cubic miles of dense rock equivalent
were ejected into the atmosphere.
Photo courtesy of U.S. Department of Interior
As the magma chamber emptied, the enormous pyroclastic column collapsed upon itself and smashed into the island. The massive base surge that resulted radiated out across the sea for miles in every direction, an unstoppable wall of superheated ash, smoke, and debris hurtling across the water at speeds nearing 100 miles per hour. Ships caught at sea were instantly swamped and sunk. Nearby islands were scoured by the pyroclastic flow, and the scorching carbon monoxide and sulphur gases suffocated every living thing in their path.
Days later, having spent itself, the volcano collapsed inward leaving a hole in
the sea seven miles long, four miles wide and over 1300 feet deep. Millions of
tons of water rushed in to fill this void draining the surrounding sea, only to
be forced back out away from the shattered remains of the island. The sudden
outward resurgence of seawater generated a tsunami that towered ten stories
above the surface. Anything not swept away by the base surge was consumed by a
tidal wave one hundred feet high.
Photo courtesy of Frederic N. McMachan III / www.coolacrylix.com
The looming wall of water raced across the Mediterranean, inundating the small islands nearby and smashing coastal villages from Alexandria to Gibraltar. Thousands of people were drowned or swept out to sea. Any ship caught on the surface was swamped and sunk instantly. The Therans who had evacuated their homes would have arrived on Crete only days, perhaps hours before the ports were smashed and the fleet of merchant ships demolished. It is likely that many were lost at sea before ever reaching safety. High above the destruction, a dense cloud of ash turned daylight to darkness. It would have seemed to the survivors as if the world had come to an end.
It is estimated that Thera erupted continuously for two to three days, shrouding the Aegean in darkness. Some researchers believe it lasted even longer. The prevailing winds swept much of the ash and light density debris to the east and north, although fallout covered an area spanning the entire eastern half of the Mediterranean. Pumice rafts floated on the sea surrounding Thera for days or even weeks, in some places thick enough for a man to stand upon.
Photos courtesy of Michael Lahanas / photoshop by Mark Nobles
Coastal towns and seaports had been smashed by the tsunami, with damage ranging inland for more than a mile. The bright Aegean sun was barely visible through the dense clouds of ash, and at times was blotted out altogether. Buildings close to the blast had been damaged or even flattened by the shock waves and millions of tons of falling debris. Although it cannot be determined exactly how many people were affected, it is certain that thousands of people and livestock were killed, and crops were smothered and destroyed by ash. Thousands more would suffer from the inevitable food shortages to come.
The climate of the planet changed as thick clouds of ash blocked out the sun. A volcanic winter had begun that stunted the growth of all manner of flora around the world. Oak forests in northern Europe and Scandinavia show several years of very limited development which coincide with the estimated date of the eruption. On the other side of the globe, forests of pine in northern California exhibit the same patterns of inhibited growth. Documents from ancient China describe instances of frost during the summer, which destroyed rice crops and led to widespread famine. It is thought that these events, which coincide with the timeframe of the Minoan Eruption, were influential in the downfall of the Xia Dynasty of China.
The Minoans recovered slowly from the catastrophe and their
influence continued for another two centuries. They would never recapture their
original grandeur, however. Once thought to be the swan song of the Minoan
culture, the eruption of Thera did not bring about their collapse, but it did
weaken their power. The most recent hypothesis suggests that Minoans were
sufficiently diminished by the cataclysm to allow Mycenae an opportunity to
conquer Crete and all its colonies. By 1400 BCE, the Minoans were merely a
chapter in the history of the ancient world.
Artwork courtesy of www.ancient-greece.org
Thera in the Modern World
The precise date of the Theran Eruption is not known, although in 2006 a discovery was made which was beneficial in significantly narrowing the historical timeframe. The remains of an olive tree were discovered buried in the tephra near Akrotiri. The tree was still vertical, indicating that it was alive at the time it was buried, and the carbon dating of samples of this tree point to a time period between 1627 and 1600 BCE. There are numerous problems that arise with this date, however, in that the timelines of many of the Mediterranean cultures must be shifted to accommodate the date of the eruption. This is no easy task, as it involves reexamining the entire histories of Egypt, Greece, and Mesopotamia, which have long been established by the archaeological and anthropological remains of those cultures. Ancient documentation of the Theran Eruption does not exist, although it must be stated that the Minoan language has yet to be translated. It is possible that some record of the disaster does exist, albeit wrapped in an alphabet that is indecipherable at this time. The only written record we can refer to is Platoís dialogues Timaeus and Critias, written some twelve centuries after the eruption.
In these writings, Plato speaks of Atlantis, a powerful naval empire that had conquered much of Africa and Western Europe. Of course, there is no evidence to support the idea of Atlantis ever having existed, but there are elements of the Minoan culture that could easily be interpreted as such, and for this reason it is a popular idea that Thera was the seed from which the Legend of Atlantis grew.
In spite of the lack of written records, vulcanologists have been able to determine many of the facts relating to the eruption of Thera by studying the records of more recent and well documented volcanic eruptions. Frequent comparisons are made to the 19th century eruption of Krakatau. Like Thera, Krakatau is a shield volcano, which erupted explosively in May of 1883.
like Thera, Krakatau collapsed in upon itself after having obliterated two
thirds of the island. The volume of dense rock equivalent, or DRE, was
considerably less, however. Krakatau ejected slightly less than six cubic miles
of rock, ash and pumice, whereas the Theran eruption displaced fourteen cubic
miles of DRE.
Artwork courtesy of Mark A. Garlick / www.space-art.co.uk
When Krakatau exploded, the blast was heard in Alice Springs, Australia, over 2100 miles away, and the concussion shattered windows in a sixty miles radius. The resulting tsunami was nearly 100 feet high and affected the entire Indian Ocean, reaching as far west as Africa. The destruction caused by Krakatau flattened more than 160 villages and towns, and damaged another 132. The pyroclastic flow spread out across the sea, and reached portions of Java twenty-five miles away. More than 36,000 people were killed as a result of this eruption and itís after effects. Thera was even more violent and destructive than Krakatau, but the similarities between the two are sufficient to give researchers a clear idea about the details of the Theran eruption.
The similarities continue: Like its Indonesian counterpart, Thera is very much
alive to this day. In 197 BCE, a new island emerged in the caldera as a result
of subsurface eruptions. This island, known as Palea Kameni, was joined by yet
another, known as Nea Kameni, in 1866. Since its emergence, Nea Kameni has grown
much more rapidly than its older sibling, and is today a tourist attraction.
There have been eleven recorded eruptions since the Bronze Age, four in the last
100 years alone. It seems inevitable that more will follow.
Photo courtesy of Brent Welton, University of Virginia, Richmond
Photo courtesy of Brent Weller
Today the island of Santorini is part of Greece, and home to some five thousand
Hellenes. It is a paradise to which tourists flock, as evidenced by the
countless cruise ships that frequent the harbor. It is also a recurring point of
interest for researchers of all varieties; archaeologists, anthropologists,
vulcanologists, and even the scores of people who search for Atlantis. The world
can only speculate at what secrets lay beneath sixteen stories of volcanic rock
and ash, and perhaps one day the 3600 year old history of the Minoan people will
finally be known. What is certain is that Santorini is still a very active
volcano with its own very destructive history. There is no way of knowing when
it will erupt again, nor how violent it will be. We can be assured, however,
that it will continue to erupt and grow, as it has done for hundreds of millions
Photo courtesy of www.windmillstravel.com
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