Until relatively recently, the world experienced several earthquakes exceeding the magnitude of 9 magnitudes. These were both the earthquake that caused the devastating tsunami of 2004 and the earthquake that led to the disaster at the Fukushima nuclear power plant. However, evidence discovered and researched by archaeologists suggests that at least as strong an earthquake 3800 years ago struck the people of the Chilean coast for a long time.
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What does this mean? Archaeologists have analyzed both the remains of man-made structures on the coast and samples of coastal stones and pebbles found deep inland, as well as the remains of aquatic inhabitants that should not be there.
“We found evidence of sea sediments and also of many aquatic animals that spent their days at sea, suddenly thrown so deep inland that it couldn’t be done by a normal storm,” Live Science quoted James Gof, a geologist at the University of Southampton, as saying. They are found in the Atkamac Desert, 600 kilometers from the coast. Researchers believe that an extremely huge tsunami could do just that.
The remains of historic stone buildings found in the coastal area also show that their capabilities have been destroyed by enormous force. Remains of walls found under the tsunami’s sediments have often collapsed towards the sea, indicating that they have been destroyed by very strong tsunami recurrence currents.
In total, geologists in this study analyzed 17 different samples of marine sediments from seven different excavation sites hundreds of kilometers from the shoreline. Radiation-14 dating with radioactive carbon-14, one of the most popular and accurate methods for determining the age of organic materials, was used to determine the age of marine shells and other remains found there. Scientists estimate that these marine materials were dumped inland about 3,800 years ago, when the earthquake struck.
Of course, without direct observations and seismographic data, it is difficult to accurately estimate the magnitude of this devastating earthquake, but it is quite possible that it has surpassed the well-known and well-documented megatrocks. Significantly, even in the age of modern measurements, the strongest earthquake – the 1960 Valdivia earthquake – occurred in Chile (also known as the Great Chilean Earthquake). Its magnitude was 9.5, and the earthquake claimed the lives of several thousand people. Like the Valdivia earthquake, an ancient earthquake off the coast of Chile was pressed against the edge of one tectonic plate with great force. At some point, the two plates “lock together” again due to friction and stop moving, but the forces that guided the collision of these plates continue to act. At some point, the mechanical stress builds up so much that a fracture occurs at the plate collision, releasing large amounts of energy in an instant in the form of seismic waves. It is also an earthquake.
Archaeologists have found that this natural disaster has contributed to such a major social upheaval in coastal communities that they have moved relatively deeper inland for fear of a repeat tsunami. “People returned to the coastal zone only after some 1,000 years, which is a very long time, given that their survival depended heavily on seafood before,” says Gofs. He and his colleagues will continue to study geological developments in the region and hope that his work will allow them to better anticipate and prepare for future megatrocks. At the time, the earthquake and the ensuing tsunami devastated the lives of the people of the Chilean coast alone. Although the tsunami hit even New Zealand and certainly devastated many of the islands on the way, many of the islands in the South Pacific were uninhabited at the time. “They are now populated and many are popular tourist destinations. In the future, the consequences of an earthquake of a similar magnitude could be truly catastrophic,” the scientist warns.
The work of Gofa and colleagues can be read in the scientific journal “Science Advances“.
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