A major earthquake struck Chile’s Atacama Desert about 3,800 years ago, severely disrupting prehistoric communities

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)—Scientists have unearthed evidence for a major earthquake that struck the arid Atacama Desert region along the Chilean coast about 3,800 years ago, triggering a tsunami and severely disrupting prehistoric communities. Diego Salazar and colleagues observed that, following the disaster, the hunter-gatherers in the area adapted largely by abandoning their settlements. However, knowledge of these major events seemed to fade with time – residential sites arose near the shoreline once again by about 1,000 years ago. The authors suggest that Atacama residents may not have anticipated the earthquake because events of this scale only occur in the region over large time intervals. “These results should also be used to recalibrate current hazard assessment policies, which, for coastal northern Chile, are mostly based on the historical tsunamigenic earthquakes,” Salazar et al. write. Due to a lack of interdisciplinary research, scientists’ understanding of prehistoric megathrust earthquakes – monstrous quakes that occur in zones where one tectonic plate is forced beneath another – has not been sufficient to assess how humans have responded to these events in the past.  To evaluate the existence of a megathrust earthquake that happened almost 4,000 years ago and to understand its social impact, Salazar et al. gathered a combination of geological and archaeological evidence. They measured 17 radiocarbon ages for littoral deposits – sandy remnants of the ancient sea laced with shells – at 7 sites, determining that the deposits provide evidence for coastal uplift along the northern Chile seismic gap during this period. The researchers also found that buildings at 5 archaeological sites along the coast concurrently became eroded or were destroyed. Salazar et al. discovered that extensive mining at one site ceased following the quake and human occupation throughout the region was reduced to a smaller number of less populated sites.

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Earthquake driven uplifted paleo-beaches at Zapatero archaeological site. Gabriel Easton

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