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The devastating volcanic eruption of Thera in the Bronze Age (dated to ca. 1630-1600 BC geologically, but to ca. 1500 BC archaeologically) has become the most famous single event in the Aegean before the fall of Troy. The eruption would likely have caused a significant climate upset for the eastern Mediterranean region. It was one of the biggest volcanic eruptions on Earth during the last few thousand years.

Since the closest civilization to Thera at this time was Minoan Crete, this is often colloquially labeled the "Minoan eruption".

Physical effects of the eruption

The violent eruption was centred on a small island just north of the existing island of Nea Kameni in the centre of the caldera. The caldera itself was formed several hundred thousand years ago by collapse of the centre of a circular island caused by the emptying of the magma chamber during an eruption. It has been filled several times by ignimbrite since then and the process repeated, most recently 21,000 years ago. The northern part of the caldera was refilled by the volcano and then collapsed again during the Minoan eruption. Before the eruption, the caldera formed a nearly continuous ring with the only entrance between the tiny island of Aspronisi and Thera. The eruption destroyed the sections of the ring between Aspronisi and Therasia, and between Therasia and Thera, creating two new channels.

On Santorini, there is a deposit of white tephra thrown from the eruption; it is up to 60 metres thick overlying the soil marking the ground level before the eruption. The layer is divided into three fairly distinct bands indicating different phases of the eruption.

A series of warning earthquakes must have been alarming enough and early enough before the eruption for all the residents to pack up and move out, as not a single body has been found at the Akrotiri site. (The single body found on Therasia has now been identified as a much earlier funerary burial.) The thinness of the first ash layer and the likelihood of this layer being eroded by winter rains indicate that the volcano may have given warning at most months in advance and not years as previously believed . It remains to be seen if further excavations will show bodies of people huddled along the coast, too late to get off in a boat to escape the volcano's fury, akin to the finds at Herculaneum, which was buried by the much smaller eruption of Mount Vesuvius in 79 AD.

In a classic Plinian eruption marked by columns of smoke and ash extending high into the stratosphere, the Minoan eruption created a plume 30-35 km in height, and magma coming into contact with the shallow marine embayment would have caused a violent phreatic eruption. The eruption also generated a 35 to 150 m high tsunami (estimates vary) that devastated the north coast of Crete, 110 km (70 mi) away. The impact of the tsunami pummelled coastal towns such as Amnisos, where building walls have been knocked out of alignment. The tsunami would also certainly have eliminated every timber of the Minoan fleet along Crete's northern shore. On the island of Anaphi, 27 km to the east, ash layers 10 feet deep have been found, as well as pumice layers on slopes 250 meters above sea level. Elsewhere in the Mediterranean there are pumice deposits that could be caused by the Thera eruption *. Ash layers in cores drilled from the seabed and from lakes in Turkey, though, show that the heaviest ashfall was towards the east and northeast of Santorini. (Ash found in Crete is now known to have been from a precursory phase of the eruption, some weeks or months before the main eruptive phases, and would have had little impact . Santorini ash deposits were at one time claimed to have been found in the Nile delta, but this is now known to be a misidentification .)

The volume of ejecta is estimated to have been up to four times what was blown into the stratosphere by Krakatau in 1883, a well-recorded event, placing the VEI (Volcanic Explosivity Index) of the Thera eruption at 6. Every vestige of life is likely to have been eliminated or smothered in the Thera ashfall, leaving an island that had essentially been sterilized, as was Krakatau.

Dating the volcanic eruption

The Minoan eruption provides a fixed point for aligning the entire chronology of the 2nd millennium BC in the Aegean, because evidence of the eruption occurs throughout the region. However, its exact date is unknown. Current opinion based on radiocarbon dating indicates that the eruption occurred between about 1630 and 1600 BC. These dates, however, conflict with the usual date from archaeology, which is around 1500 BC.

There are numerous archaeological chronologies for the Late Bronze Age, each based on a point of origin for a given material culture. International commerce shipped material culture from Crete, mainland Greece, Cyprus, and Canaan to contexts throughout the eastern Mediterranean. If the Thera eruption could be dated and then associated with a given layer of Cretan (or other) culture, chronologists could use that layer of culture to date other events. Since Thera's material culture at the time of destruction was most like the "Late Minoan IA (LMIA)" culture on Crete, LMIA is the baseline for relative chronology elsewhere. The eruption also aligns with Late Cycladic I (LCI) and Late Helladic I (LHI) - but before "Peloponnesian LHI". (c.f. On the Late Helladic I of Akrotiri, Thera) As of 1989, Akrotiri had also yielded fragments of nine Syro-Palestinian "Middle Bronze II (MBII)" gypsum vessels. Summary of Evidence for the Absolute Chronology of the Early Part of the Aegean Late Bronze Age Derived from Historical Egyptian Sources

Some scholars believe the radiocarbon dates to be problematic or completely wrong. Some suggest re-scaling archaeological chronologies with the radiocarbon dates. Others look for a compromise between the archaeological and radiocarbon dates for best fits of both sets of data. Re-scaling archaeological chronologies is controversial, because revising the Aegean Bronze Age chronology could require, by association, revising the well-established conventional Egyptian chronology. The debate about the date continues.

It has long been hoped that information from Greenland ice cores and dendrochronology would determine the date exactly. A large eruption, identified in ice cores and dated to 1644 +/- 20 BC years was suspected to be Santorini. Tree ring data shows that a large event interfering with normal tree growth in America occurred in 1629-1628 BC *. These events had formerly been associated together.

But volcanic ash retrieved from an ice core demonstrated that this was not from Santorinihence, the 1644 BC date is incorrect. Instead, separate Greenland ice-core samples suggest that there was another eruption in about 1623 BC.[http://topics.nytimes.com/top/news/science/topics/ice/index.html?query=SANTORINI&field=geo&match=exact That last agrees better with the date from dendrochronology.

On 28 April 2006, the journal Science published two research papers arguing that new radiocarbon ages required an eruption date between 1627 and 1600 BC. The research published by Manning et al. in their Science paper analysed 127 samples of wood, bone, and seed collected from various locations in the Aegean, including Santorini, Crete, Rhodes and Turkey. The samples were analysed at three separate labs in Oxford, Vienna, and Heidelberg in order to minimise the chance of a radiocarbon dating error. Manning's research offered a broad dating for the Thera event between 1660 to 1613 BC. The other Science paper, by Friedrich et al., narrows the time-line for the eruption of Thera to between 1627-1600 BC on a 95% probability, which was facilitated by the rare discovery of an olive tree which had been buried alive on Santorini under a layer of lava rock. [http://www.sciencemag.org/cgi/content/abstract/sci;312/5773/548 Because the tree grew on the island, though, it cannot be certain that its growth was unaffected by volcanic degassing (which would render the radiocarbon ages too early).

The same issue of the journal Science also includes an article quoting eminent archaeologists (Peter Warren and Manfred Bietak) expressing strong scepticism on the new information. At present, then, there is still a dispute between those who believe the radiocarbon data and those who believe in the traditional Aegean chronology. Now that the new radiocarbon dates are published, they will need to be considered by other scholars. It is worth noting that in the past a definitive date for the eruption of Thera has been claimed many times; yet later analysis has always shown such claims to be flawed in some way due to difficulties with radiocarbon methodology or other reasons. Firm conclusions cannot be drawn at the present time.

The "Aniakchak eruption"?

Even if the c. 1645 BC ice core is non-Theran, it still represents a volcanic eruption that could potentially affect climate. Recent dendrochronological findings further show that growth anomalies at Porsuk in Anatolia might have occurred in c. 1645 BC, and not c. 1628 BC. (A Dendrochronological Framework for the Assyrian Colony Period) These unusually wet (and therefore, in this latitude, cold) summers, if volcanic in origin, could be the result of climate change from a non-Theran eruption.

N. Pierce and others in 2003 published an article entitled "Reinterpretation of Greenland Ice-core data recognises the presence of late Holocene Aniakchak tephra" in the Proceedings of the SCIEM 2000 Euro-conference. Aniakchak is a volcano in Alaska. This possibility is still in dispute.

Effects on human civilizations

Volcanic eruptions can impact human civilizations by earthquakes, ashfall, and tsunamis, and worldwide climatic effects such as volcanic winters. The impact of Santorini's massive eruption on civilizations of its time are not well understood and are still open to speculation.

Impact on Minoan civilization

Tsunamis from the pyroclastic flows and caldera collapse would have devastated the navy and ports of the Minoans on the north side of Crete. Being that the Minoans were a sea power and depended on their naval and merchant ships for their livelihood, the Thera eruption must have impacted the Minoans to some degree. Whether these effects were enough to trigger the downfall of the Minoans is under intense debate. Significant Minoan remains have been found above the LM I-era Thera ash layer, implying that the Thera eruption did not cause the immediate downfall of the Minoans. The Mycenaean conquest of the Minoans occurred in LM II not many years after the eruption, though; and many archaeologists speculate that the eruption induced a crisis in Minoan civilization, which allowed the Mycenaeans to conquer them.

For instance, Jan Driessen (in Aegaeum 22) argues for "Crisis Cults on Minoan Crete" at the end of LM I, by which the palaces adopted a "Kouros"-god from the hills in addition to the Minoan goddess. One of these new idols, at Palaikastro, was subsequently vandalised. (But note that Driessen thinks that the kouros-god here and elsewhere is Diktaian Zeus; he is more likely Welchanos - c.f. Mark Alonge, "The Palaikastro Hymn and the modern myth of the Cretan Zeus", 2005.) This hints at a domestic crisis of spirit with factional strife, before the coming of the Greeks later in LM II.

Chinese records

Some scientists correlate a volcanic winter from the Minoan eruption with Chinese records documenting the collapse of the Xia dynasty in China. According to the Bamboo Annals, the collapse of the dynasty and the rise of the Shang dynasty (independently approximated to 1618 BC) was accompanied by "'yellow fog, a dim sun, then three suns, frost in July, famine, and the withering of all five cereals".

Egyptian records

Oddly, there seem to be no surviving Egyptian records of the eruption. The absence of such records is sometimes attributed to the general disorder in Egypt around the Second Intermediate Period.

Scholars J. G. Benett and A. G. Galanopoulos suggest connections between the Thera eruption and the calamities of the Admonitions of Ipuwer, a text from Lower Egypt during the Middle Kingdom or Second Intermediate Period. (During the Second Intermediate Period, Lower Egypt came under the rule of "Hyksos" from Canaan.)

Greek traditions

Oxford scholar J. V. Luce suggested in 1969 that the eruption of Thera and volcanic fallout inspired myths of the Titanomachy in Hesiod's Theogony. The background of the Titanomachy is known to derive from the Kumarbi cycle, a Bronze Age Hurrian epic from the Lake Van region; but the Titanomachy itself could have picked up elements of western Anatolian folk memory as the tale spread westward. Mott Greene compared Hesiod's lines with volcanic activity, citing Zeus' thunderbolts as volcanic lightning, the boiling earth and sea as a breach of the magma chamber, immense flame and heat as evidence of phreatic explosions, among many other descriptions. Greene concluded that Theogony "leaves no doubt that the phenomena described are volcanic eruptions."

Deucalion's flood is dated in the chronology of Saint Jerome to ca. 1460 BC.

Biblical traditions

One interesting possibility for the effects of Thera's eruption is the origin of the story of the ten plagues to which Egypt was subjected, as proposed by historian J.G. Bennett Jr. According to the Bible, Egypt was beset by such misfortunes as the transforming of their water supply to blood, the infestations of frogs, gnats, and flies, darkness, and violent hail. These effects are compatible with the catastrophic eruption of a volcano in different ways. While the "blood" may have been red tide which is poisonous to human beings, the frogs could have been displaced by the eruption, and their eventual death would have given rise to large numbers of scavenging insects. The darkness could have been the resulting volcanic winter, and the hail the large chunks of ejecta spewn from the volcano. The tsunami that resulted from the Thera eruption is also speculated to have caused the parting of the sea that allowed the Israelites, under Moses, safe passage of the Red Sea, possibly devastating the Egyptian army with the returning wave. This theory is obviously very speculative.

Association with Atlantis

Starting with Spyridon Marinatos' 1939 landmark paper, this cataclysm at Santorini and its possibility to have caused the fall of the Minoan Civilization centered on Crete is sometimes regarded as a likely source or inspiration for Plato's story of Atlantis. Detractors of the theory say that Santorini and Crete combined would not be the size of Plato's Atlantis, and the date of the Minoan collapse does not match Plato's dates for the fall of Atlantis. Scholars such as James Luce and A. G. Galanopoulos argue that the error in date and size could be caused by a mistranscription of the Ancient Egyptian or Mycenaean Linear B symbol for "hundred" as "thousand" (the former is unlikely because there would be little confusion in the visual appearance of hieroglyphic symbols of Egyptian numeric values).

References

  • Balter, Michael: "New carbon dates support revised history of ancient Mediterranean", Science 312: 508-509 (28 April 2006).
  • Forsyth, Phyllis Y., Thera in the Bronze Age (New York: Peter Lang Pub Inc., 1997). ISBN 0820448893
  • Friedrich, Walter L., & McBirney, Alexander R. *, Fire in the Sea: Natural History and the Legend of Atlantis (Cambridge University Press, 1999). A historical account of the eruption and its effects from a geological point of view with many drawings, figures and pictures.
  • Greene M.T., Natural Knowledge in Preclassical Antiquity (Baltimore: Johns Hopkins University Press, 1992). This concludes that Hesiod's Theogony contains a detailed eyewitness description of the eruption of Thera.
  • Guichard F. et al. (1993), "Tephra from the Minoan eruption of Santorini in sediments of the Black Sea", Nature 363: 610-612.
  • Heiken G. & McCoy F. (1990), "Precursory Activity to the Minoan Eruption, Thera, Greece". In: Hardy D.A. (editor), Thera and the Aegean World III, v.2, p. 79-88, London: The Thera Foundation.
  • Keenan D.J. (2003), "Volcanic ash retrieved from the GRIP ice core is not from Thera", Geochemistry Geophysics Geosystems, 4 (doi:10.1029/2003GC000608).
  • Manning S.W. et al. (2006), "Chronology for the Aegean Late Bronze Age 1700–1400 B.C." Science 312: 565-569.

External links

Archaeological sites in Greece | Minoan civilization | Bronze Age | Atlantis | Volcanic events

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Thera eruption".

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