One of the most powerful earthquakes in recorded history occurred in the Pacific Ocean just off the coast of Chile approximately 3,800 years ago. This catastrophic seismic event created a massive tsunami that battered the entire Chilean coastline, including the Atacama Desert, leaving a trail of destruction that covered more than 600 miles (1,000 kilometers).

At this time, the coastline region of Chile was inhabited by hunter-gatherer groups. Undoubtedly there was significant loss of life among these groups as a result of the earthquake and ensuing tsunami, and trying to survive in the aftermath of this devastating calamity would have been incredibly challenging.

According to a new study just released in the journal Science Advances , the hunter-gatherer groups that experienced this dual natural disaster were profoundly affected by it not just in the short term, but for generations to come. In fact, the researchers involved in this study found that these groups abandoned the Atacama Desert in Chile’s coastline region immediately after the seismic event and didn’t return in large numbers for more than 1,000 years.

A mega-earthquake 3,800 years ago, and the resulting tsunami, led to the Atacama Desert being abandoned for more than 1,000 years, claims new study. (Public domain)

A mega-earthquake 3,800 years ago, and the resulting tsunami, led to the Atacama Desert being abandoned for more than 1,000 years, claims new study. ( Public domain )

Memory of Tsunami Remained in Atacama Desert Region

This years-long study was conducted by an international team of geologists, ecologists, and anthropologists, who were looking for information about ancient seismic events and their impact on the people who resided in the earthquake zone in the distant past.

Led by geologist Gabriel Easton from the University of Chile, the research team spent years carrying out geological and archaeological surveys in the Atacama Desert , a 1,000-mile-long (1,600 km) arid stretch of land that spans Chile’s northern coast. The Atacama is the driest nonpolar desert in the world, yet 4,000 years ago hunter-gatherer groups had established a presence there and had learned how to survive on what the land could provide.

During their ongoing excavations, the researchers eventually reached a deep layer of sediment they were able to determine had been left behind by an enormous ancient tsunami. Radiocarbon dating of charcoal pieces and shells revealed the layer had been deposited in approximately 1,800 BC. The earthquake-induced storm left a thick pile of debris that extended an immense distance southward and northward. Given how far inland the sediment layer extended, the tsunami must have created waves that were 50 to 65 feet (15 to 20 meters) above sea level.

The scientists knew a tsunami this gigantic and destructive could only have been caused by an epic earthquake, of a record-smashing variety. “We propose that this earthquake was similar to the Valdivia earthquake that occurred in 1960 in southern Chile,” Dr. Easton told New Scientist . “This is the largest earthquake ever recorded in history.” The Valdivia quake was measured at magnitude 9.5, a number that no other seismic event has come close to matching.

Satellite image of the Atacama Desert on the coast of Chile from NASA World Wind. (Public domain)

Satellite image of the Atacama Desert on the coast of Chile from NASA World Wind. ( Public domain )

1,000-Year-Long Abandonment of the Atacama Desert

Despite the incredible flooding that must have covered the Atacama Desert with a newly formed inland sea following this natural disaster, eventually the water would have been absorbed into the super-dry soil, restoring the area to its normal desert conditions. But after this happened, it seems the people who’d lived there before did not return. For an exceptionally long time.

Ancient hunter-gatherers survived in the Atacama Desert by fishing and by harvesting other types of seafood from the beaches and off the ocean floor. But archaeological excavations tracked a sudden cessation of human activity in the area following the mega-earthquake. Some archaeological sites showed signs of occupation during the post-quake period, but it was clear that far fewer people were living there or spending time there after this traumatic and unforgettable event occurred.

In addition to changing their migration and occupation habits, the hunter-gatherers also relocated their cemeteries inland and to higher spots. Many of the bodies that were moved were mummified, and the care taken with the reburials showed how committed the people were to honoring and protecting their departed ancestors. “The most important thing that the families and the communities had at that time were their parents,” Easton noted.

What was most remarkable about the abandonment of the Atacama Desert was how long it lasted. Even though there were still ample ocean resources to exploit nearby, hunter-gathering people didn’t start returning to their ancestors’ old stomping grounds until more than 1,000 years had passed. In some instances, the gap in occupation times surpassed 1,500 years.

“This is kind of surprising, because people usually have a short memory for this kind of event,” commented Eugenio Gayo, an ecologist and climate researcher who participated in the study. Gayo calculated that an astounding 40 generations would have passed for those who stayed away for 1,000 years. “That is a lot,” she marveled.

Without writing, ancient hunter-gatherers could only pass on warnings or historical remembrances to their descendants orally or through drawings. Somehow the survivors of the 1,800 BC seismic catastrophe did manage to pass the message along, ensuring that their children and grandchildren’s generations would stay away from Chile’s seismically active northern coast. But it seems the stories they related were so vivid and frightening that the message kept moving forward long into the future, and as a result the descendants of the survivors stayed away for centuries.

The Atacama Desert on the coast of Chile saw a mega-earthquake and tsunami 3,800 years ago. (Luca Galuzzi / CC BY-SA 2.5)

The Atacama Desert on the coast of Chile saw a mega-earthquake and tsunami 3,800 years ago. (Luca Galuzzi / CC BY-SA 2.5 )

So Why Did Hunter-Gatherers Finally Return to the Atacama Desert?

While earthquakes as large as the one that hit Chile in 1,800 BC are unusual, earthquakes in the region in general are not. The Atacama Desert on the coast of Chile is located on a subduction zone, where the adjacent Nazca oceanic plate is slowly sliding under the South American continental plate. This ongoing geological process is what created the Andes Mountains, and in Chile it causes frequent earthquakes—some of which have been exceptionally severe.

On May 22, 1960 the Valdivia mega-quake hit southern Chile. The quake and subsequent tsunami leveled many towns and cities, killing more than 1,600 thousand people and leaving more than two million homeless.

This was the strongest earthquake ever recorded, and if the quake of 3,800 years ago was of similar intensity it must have truly traumatized everyone it affected. Indeed, the long and highly unusual interruption in the archaeological record in the Atacama Desert would seem to verify the horrific and catastrophic nature of this event and its aftermath.

But what convinced the distant ancestors of the long-departed earthquake and tsunami victims to finally return, after such a long absence? It certainly didn’t happen because the risk of earthquakes disappeared. Quakes are a regular occurrence along the Chilean coastal subduction zone and, as the 1960 event proved, they can be incredibly severe and destructive.

Once again, researchers are confronted with a surprising development they cannot completely explain. There is only so much information that can be deduced from the archaeological record, meaning that some historical mysteries are destined to remain unsolved forever.

Top image: The Atacama Desert in Chile. Source: baisa / Adobe Stock

By Nathan Falde

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