The biggest earthquake in human history caused a 5,000-mile tsunami

Incredibly, it had a 9.5 magnitude.
Derya Ozdemir

What we know about earthquakes has just gotten an update.

A team of archaeologists has discovered evidence of the largest megaquake in human history.

The earthquake struck about 3,800 years ago in what is now northern Chile when a tectonic plate rupture raised the region's coastline. Its devastating repercussions drove human populations away from neighboring coastlines for 1,000 years. 

Researchers from the University of Southampton stated that it was a horrifying magnitude-9.5 megaquake that unleashed a tsunami with waves as high as 66 feet (20 meters) that traveled more than 5,000 miles (8,000 kilometers) to New Zealand, according to the study published in the journal Science Advances.

An earthquake with a magnitude of 9.5

An earthquake occurs when two tectonic plates collide and rupture, with larger earthquakes resulting from longer ruptures. While several earthquakes have wreaked havoc on Earth in recent years, the power of the Kashmir Earthquake in 2005 to the Haiti Earthquake in 2010 pale in comparison to this huge earthquake that hit northern Chile 3,800.

"It had been thought that there could not be an event of that size in the north of the country simply because you could not get a long enough rupture," James Goff, a co-author of the new study, and a geologist at the University of Southampton in England, explained in a press release. "But we have now found evidence of a rupture that's about one thousand kilometres long just off the Atacama Desert coast and that is massive."

This earthquake has updated our knowledge of the largest earthquake ever recorded. Previously, scientists thought that human history's largest earthquake was the 1960 Valdivia earthquake, which hit southern Chile with a magnitude between 9.4 and 9.6. The rupture that was the culprit of the earthquake extended as far as 500 miles (800 km) in length, which is fairly massive, and it killed up to 6,000 people. 

The newly discovered megaquake, on the other hand, was even larger, originating from a roughly 620-mile-long (1,000-km) rupture. 

Hunting down the evidence for the megaquake

The researchers found evidence for the massive earthquake in marine and coastal items like littoral deposits, such as boulders, pebbles, and sand native to coastal regions, and marine rocks, shells, and sea life. The team discovered these items displaced far inland in Chile's Atacama Desert.

"We found evidence of marine sediments and a lot of beasties that would have been living quietly in the sea before being thrown inland," Goff explained. "And we found all these very high up and a long way inland, so it could not have been a storm that put them there."

The researchers used radiocarbon dating to discover the ages of the displaced coastal material and found that they had been carried inland some 3,800 years ago. The excavation of ancient stone structures built by humans added to their findings, enabling them to see the impact of the earthquake on humans. 

"The local population there were left with nothing," Goff said. "Our archaeological work found that a huge social upheaval followed as communities moved inland beyond the reach of tsunamis. It was over 1,000 years before people returned to live at the coast again, which is an amazing length of time given that they relied on the sea for food."

Next, the researchers intend to further investigate the region with hopes in order to inform us of the potential dangers of such future earthquakes.

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