3800 years ago a tsunami surprised the coastal inhabitants of today’s Chile. The tsunami – the result of a strong earthquake – caused such severe destruction that the local people gave up their settlements, reports an international research group in the journal Science Advances. Only after a thousand years, when the memory of the catastrophe had probably died out, did people return to the coast in larger numbers.
Earthquakes and tsunamis are among the most devastating natural disasters that can affect human societies, writes the team led by Diego Salazar from the Universidad de Chile. A growing number of people are currently exposed to these risks. Since the beginning of this century, more than 700,000 people have lost their lives as a result of earthquakes, including the Tohoku quake in 2011, which led to the nuclear accident in Fukushima. In order to be able to better assess risks, such as frequency and consequences, observations over long periods of time are important, including from the past.
For their study, the scientists had carried out archaeological investigations on the Atacama coast of Chile for more than two decades. The Atacama Coastal Desert in northern Chile is an extremely dry area between Arica and Huasco. There is hardly any plant growth and practically no rainfall. In contrast, life thrives in the offshore sea: It is one of the most productive marine ecosystems and rich in fish. The reason for this is the cold Humboldt Current and the coastal upwelling. As a result, the region has been popular with hunter-gatherers for nearly twelve thousand years, including the time of the event some 3800 years ago.
An earthquake raised the coast meters high
Among other things, the researchers had looked at various archaeological sites for traces of marine organisms that had been deposited on land as a result of a tsunami. They found what they were looking for in regions that today are up to seven meters above sea level: they discovered old beaches. Changes in sea level could not explain the observation, the researchers report. They assume that a massive earthquake had lifted the coast. According to their models, the earthquake had a magnitude of 9.5.
As a result of the destruction, local hunter-gatherers and fishermen appear to have abandoned their settlements and cemeteries, further investigation showed. To adapt to the new situation, people first moved them to higher altitudes. It took a thousand years for the demographic numbers to recover, Salazar explained, meaning people settled near the coast again. But both the cemeteries and the settlements initially remained at higher elevations. Only almost 3000 years after the event did people resettle where they had settled before the earthquake.