A recent study of geological deposits and archaeological remains has identified a massive earthquake and tsunami that destroyed areas along the coast of Chile’s Atacama Desert around 3,800 years ago. Examining past disasters—and people’s responses to them—can help with today’s risk planning in seismically active coastal areas.
A forgotten tragedy
Broken walls and collapsed stones reveal the catastrophe that struck Zapatero, an ancient settlement in what is now northern Chile, about 4,000 years ago.
People who lived on the shores of the Atacama Desert 5,700 to 4,000 years ago built villages of small stone houses on top of large piles of shells (the Zapatero shell shell filled is two meters deep and has a kilometer six kilometers). Often, these houses stand close to each other, opening to interior patios. People buried their dead under the floors of the house. The concrete floor is made of algae ash, seawater and shells—the same material used to hold the stone walls together.
But stones and mortar fail in the face of the sea’s power. A house in Zapatero collapsed, and the stones on its wall collapsed as if it had been hit by a big wave. Another came with its stones scattered back to the sea, in exactly the shape expected from “strong currents associated with tsunami backwash,” said University of Chile archaeologist Diego Salazar and his colleagues. In the third floor, the floors are covered with crushed sand containing the remains of marine algae and echinoderm spines, mixed with pieces of rock, shells, and broken sediments. from the ground.
Elsewhere on the Zapatero midden, Salazar and his colleagues found similar layers of sand and torn-up ground left by the old tsunami, with channels that had been left by the strong tsunami, the sudden current. When the archaeologists radiocarbon-dated the shells from these layers, they found that many of the shells were older than those in the undisturbed layer below—evidence that just broke the ground and tore these old shells from their resting places to put them. the surface
The same story is written in the ruins and sediment at other ancient sites along the hundreds of kilometers of Atacama coast. In recent studies, Salazar and his colleagues also found geological evidence of the earthquake and tsunami that hit the area: layers of sandy, shelly sea sediments were raised several meters above sea level by turbulence earthquake The researchers radiocarbon-dated whales in these elevated chunks of the old coast, along with whales and coal in the layers above and below the tsunami deposit, and narrowed the date of the ancient disaster to around 3,800 years ago, for or take a century or two.
Combined, geological studies and archaeological evidence point to a natural disaster of extreme proportions: a rupture along the 1,000-kilometer length of the fault system where the Nazca Plate is sliding beneath the South American Plate. An estimated 9.5 megathrust earthquake would have pushed parts of the coast up and caused a tsunami 19 to 20 meters high along a large stretch of the Chilean coast (and all the way across the Pacific in New Zealand, where scientists have also seen the deposits from tsunamis of the same age).
The combined earthquake and tsunami wreaked havoc on the ancient people who lived near the Pacific Ocean with a barren desert behind them. Archeological evidence shows that people left the coast for centuries after the disaster.
Abandoned villages and scattered camps
The Atacama Desert is a tough place to live. It is the driest desert in the world outside of Antarctica, with less than 1 millimeter of rain a year. But people have lived—and thrived—here for at least 12,000 years. In part, they are pulled away by turning to the sea.
Just outside, the Humboldt Current surges with nutrient-rich water, creating a rich, coastal ecosystem that’s also home to one of the world’s most productive fisheries. Thanks to the long, slow tectonic collision between the Nazca Plate and the South American Plate, the area is also prone to earthquakes. But for thousands of years, people traded that product sporadically, a long-term threat to the ocean’s riches. They left archaeologists with evidence of their presence and their adaptations to life in this unique environment.
But after an earthquake and tsunami 3,800 years ago, people left the shell settlements and stone houses on the Atacama coast. The sea has always been essential for life in the Atacama, but it is clear that, for centuries, no one wanted to live near it.
Above the levels of sand and debris from the waves, mixed with mud walls, there is little or no impact of human activity in places like Zapatero. The only evidence speaks of very brief visits: small towers and a scattering of artifacts lying atop flood debris and broken stone walls. When the people had to return to the ruins of their ancestors, it was clear that they did not want to stay long.
Scientists can see that caution in the abandoned buildings and temporary camps in places like Zapatero, but they can also read in the huge changes that take over the entire northern coast of Chile. Approximately 100 kilometers near Taltal, a region of northern Chile rich in archaeological sites, a study revealed a 65 percent decrease in the number of settlements after the last 3,800 years.
That date is not only the arrival of the tsunami, but the border between the two archaeological cultural periods, Archaic IV (5,700 to 4,000 years ago) and Archaic V. After that border, the settlements did not decrease, and both buildings and cemeteries tend to be. further inland and on high ground. Closer to the coast, what settlements there are are fewer, with the few artifacts left buried and scattered.
My ex got the tool
Even very important resources, like the iron oxide mine in San Ramón, were abandoned.
“We use iron oxide as a color for many reasons, including recognizing the pictures on the stones that can be found in many places in this area of the coastal Atacama desert,” University of Chile geologist Gabriel Easton, co-author of recent study, told Ars. These pigments seem to be important to local communities and are involved in their rituals and ceremonies.
The three-centimeter-thick mine wall may have been caused by an earthquake 3,800 years ago, and after that, activity seems to have stopped. “San Ramón 15 site is one of the oldest (pieces) of evidence of mining activity in the Americas, used since 12,000 years ago, and abandoned after 4,000 years ago, most likely due to impacts caused by an earthquake in the area,” Easton told Ars.