Mega 1,800 BC Pacific Tsunami

Scientists discover evidence for ancient super-earthquake in Northern Chile.


In about 1800 BC, a massive tectonic plate rupture lifted the coastline of northern Chile, caused a magnitude 9.5 earthquake and a 8,000km-long tsunami that created waves as high as 20m and travelled all the way to New Zealand. Car-size bounders tumbled hundreds of miles inland. Human groups living at the coast abandoned the shore for 1,000 years.


This newly discovered tremor was a megathrust earthquake, the most powerful from of such earth movements. Such quakes occur when two tectonic plates are forced above the other. It was far larger than the (9.4-9.6) Valdivia earthquake that shook the same region in 1960, killing as many as 6,000 people, and also causing a major tsunami.


James Goff, a geologist at Southampton University and team found evidence for the earthquake in both terrestrial and marine deposits, including fossils of shells and sea life that had been thrown far inland and to considerable altitudes. Using radiocarbon dates from 17 deposits extending over 600km, the geologists dated the washed ashore coastal materials to about 3,800 years ago.


Then there was archaeological evidence. Stone structures and walls built by humans came to light under the tsunami deposits, having been toppled by the incoming waves. Ten centuries passed before people settled once more at the coast – a very long time, given that molluscs and seafood were major components in local diets.


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Image: Collapsed stone structures at the Zapatero site, impacted by the tsunami.

Credit: Gabriel Easton