Over four pages, The Times Higher explores the long-term impact of the Indian Ocean tsunami and examines what can be learnt from past natural disasters

The Santorini eruption 3,500 years ago, and its aftermath, could explain upheavals on Minoan Crete, Colin Macdonald and Carl Knappett argue

The devastating tsunami that hit the Indian Ocean littoral after Christmas has refocused attention on an event that took place in the Mediterranean about 3,500 years ago - the eruption of the Santorini volcano in the Aegean Sea. This island was home to a flourishing maritime settlement whose archaeology reflects strong contacts with the contemporary Minoan civilisation of Crete some 60 miles to the south.

In 1939, Spyridon Marinatos, later the excavator of Akrotiri on Santorini from 1967-74, proposed that Minoan civilisation had been virtually wiped out by the effects of the eruption, notably a gigantic tsunami. Now archaeologists know that the eruption took place several generations before the palatial centres and other settlements on Crete were violently destroyed by fire. Strangely, Marinatos suggested that tsunami caused the destructive conflagrations.

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Over the past 30 years, a tremendous amount of archaeological, geological, volcanological and other research has been carried out to determine when and how the eruption occurred and precisely what effects could be expected on Crete. Material evidence on Crete for the eruption has proved surprisingly elusive. Early on, it was clear from numerous cores in the ocean bed that most of the tephra (volcanic ash) had been blown east and southeast of the island. Archaeologists have since been finding tephra from this eruption of Santorini in early Late Bronze Age levels at sites in Turkey, the Dodecanese Islands and in eastern Crete, confirming the results of the sea-bed cores.

At Palaikastro, a site in eastern Crete, ash layers have been found and a prestigious building area of about 1,000m2 was razed and abandoned after the eruption. Then two deep new wells were dug - a phenomenon noted throughout Crete after the eruption - perhaps because old wells had been contaminated. The street system at Palaikastro was also disrupted and ash clogged the drains. Yet there is no evidence of tsunami here, and much of the damage will have been inflicted by a tectonic (not volcanic) earthquake and then by the ash-fall that would have poisoned wells and killed pasture and crops affecting the livelihood of every citizen.

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Palaikastro, because of its geographical position, may have avoided the full force of tsunami coming from the north. However, Mochlos and Pseira, islets on the north coast, would have been directly in its path. Mochlos, in particular, has yielded evidence of substantial ash-fall, yet no obvious evidence of tsunami. Is this a question of the archaeologist not knowing what to look for? Or are the tsunamis caused by the eruption of Santorini merely imaginary?

Recent work by D. Dominey-Howes (published in the Journal of Volcanological and Geothermal Research last year) looking for tsunami deposits - silt, marine shells and microfossils and other debris - in the southeast Aegean, including Crete, has drawn a blank. The severity of the Minoan tsunami may have been exaggerated though more research is needed before the tsunami hypothesis can be dismissed. One obvious area that requires investigation is the marsh plain around the palace at Malia - since heavy erosion over the past 3,500 years may have removed much of the evidence left by tsunamis elsewhere in Crete, whereas at Malia this does not seem to be the case. In addition, more work needs to be done in the west of the island because, as Dominey-Howes has noted, the geography of Santorini, with its non-volcanic southern part of the caldera basin, would lend itself to the propagation of tsunami towards the west and southwest. So, we would have tephra travelling in one direction causing ash-related damage, and tsunami travelling in the other direction, with different physical consequences.

That said, it is certain that crucial changes were set in motion on Minoan Crete after, and probably by, the eruption. An earthquake had hit the main sites of northern Crete in Late Minoan IA (16th century BC) at about the time the eruption occurred. The Minoans were used to earthquakes and normally picked up the pieces, rebuilt and carried on. However, this double disaster, with the eruption being visible from every elevated place in Crete, appears to have been a catalyst for economic, social and religious change. Parts of settlements were abandoned, and renovated buildings had their rooms subdivided. There was a greater emphasis on storage facilities, a sensible reaction to events that resulted in widespread famine, particularly in the east where ash-fall would have devastated the farming economy in at least the short term.

Ritual references to the eruption are evidence of its effects on the Minoan psyche - pumice found as offerings at the entrance to the Arkalochori cave, at Nirou Chani and Amnissos on the coast near Knossos, and at Petras and Zakros in the east. At the same time, there was an intensification of ritual activity, symbolised at Knossos by some of the finest relief frescoes ever painted, including the Prince of the Lily Crown thought by some to be a divinity in Minoan guise. In times of great stress, people turn to religion and religious authorities, if so inclined, and can take advantage of this very human response of dependency. A minister of the church remarked after the recent tsunami that disasters made his job easier. The Minoan religious authorities may have felt the same way. Ritual intensification was also accompanied by some excesses, notably the sacrifice and perhaps eating of four or five young people at Knossos, their remains being found in a cult archaeological context.

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Most of these actions and developments can plausibly be explained by the physical and psychological impact of the Santorini eruption. Decades after the eruption, destructions swept the island; these were perhaps caused both by nature (earthquake) and man (attack). At some sites, there appears to have been wanton destruction with particular attention paid to objects of a sacred nature - notably relief stone vessels smashed and the great ivory Kouros statue at Palaikastro, perhaps a prehistoric representation of Zeus, broken in pieces and scattered as the buildings collapsed. The perpetrators of such destruction in the east of the island, which had borne the brunt of the ash-fall, could have been the local population themselves, revolting against the religious authorities that had grasped so much power in the wake of the eruption.

This last reconstruction of tenuously connected events is one scenario. The reality may become clearer as we observe some of the developments in societies affected by the Indian Ocean tsunami.

In addition, we need to do further work to assess the extent and impact of the Minoan tsunami, particularly by looking at the west of the island where the archaeology is less well known. Ironically, the idea of a Minoan tsunami was generated in part by the obvious comparison between the eruptions of Santorini and that in 1883 of Krakatoa, the volcano adjacent to the fault line where the recent earthquake took place. The main difference is that Santorini lies in an enclosed basin riddled with landmasses and islands so that the behaviour of volcanological tsunami are bound to be substantially different. Modern natural disasters give insights into past events. Unfortunately, in prehistory we are a long way from being able to use what evidence we have to assist the present.

Colin Macdonald is an archaeologist at the British School in Athens and Carl Knappett is a lecturer in archaeology at Exeter University.

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