As scientists expand their search, they have continued to find ancient tsunamis bigger than those found in historical records, says James Goff, a paleotsunami researcher at the University of Southampton in England. The implications are clear: if a huge tsunami happened once in a given location, it could happen again. The question is whether we\u2019re prepared for it.<\/p>\n
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A tsunami is more than just a big wave. Conventional waves, even those tens of meters high, are usually generated by the wind and involve only the uppermost layers of water. They carry relatively little energy, and typically crash harmlessly on the shore.<\/p>\n
A tsunami, by contrast, is spawned by geological forces\u2014an earthquake, volcanic eruption, or the side of a mountain crashing into the sea<\/a>. A tsunami involves the entire water column. While large tsunamis can measure 20 meters or more in height\u2014with some particularly monstrous ones rising hundreds of meters<\/a>\u2014they need not be exceptionally tall to cause widespread damage. Instead of collapsing on the beach, a tsunami rushes ashore like a battering ram. After racing hundreds of meters or more inland, the water recedes into the depths, carrying away nearly everything in its path. But tsunamis almost always leave evidence of their passage\u2014like an out-of-place boulder high in the desert.<\/p>\n Goff has been searching for ancient tsunamis for almost three decades, mostly in countries bordering the Pacific Ocean. He\u2019s one of just a few scientists worldwide who specialize in finding evidence of paleotsunamis, or tsunamis that predate written records.<\/p>\n The easiest way to tell that a tsunami hit hundreds or thousands of years ago is to look underground, Goff says. When the wave recedes, it leaves traces of everything it contained strewn across the surface. This thin layer of silt, rocks, tiny shells, and other marine deposits gets buried over time, preserving the tsunami\u2019s path between layers of sediment. In some places, the layers are so well preserved that researchers can see evidence of multiple tsunamis stacked on top of each other like a layer cake.<\/p>\n An excavation in Maui, Hawai\u2018i, shows four bands marking tsunami deposits. Scientists have yet to deduce when these tsunamis occurred. Photo by Scott Fisher<\/p><\/div>\n In southern Chile, you can dig a hole near many coastal rivers and count the bands. \u201cOne, two, three, four,\u201d Goff says. \u201cAnd you can just see these layers, and you know that they\u2019re paleotsunamis.\u201d<\/p>\n In places with rocky or more barren terrain, a paleotsunami\u2019s track can be harder to discern, and the techniques used must be tailored to the environment. Goff and other researchers also look for microscopic marine organisms like diatoms and foraminifera, ancient DNA from marine life, changes to geochemistry, and, as in the Atacama, unexpected boulders.<\/p>\n That Atacama tsunami likely happened in 1420, says Tatiana Izquierdo, a paleotsunami researcher based at the University Rey Juan Carlos in Spain who helped to discover it. She and her colleagues dug underneath the boulder<\/a> to find undisturbed sediment. They radiocarbon dated some of the marine shells they found, giving a range of potential dates from the 14th to the 16th centuries. With further research, the team found historical records of a tsunami in Japan in 1420 that fit with their dates. Izquierdo says their tsunami likely originated off the Chilean coast following a large earthquake and crossed the Pacific to Japan.<\/p>\n In other cases, paleotsunami researchers have drawn insights from the archaeological record. Izquierdo says archaeologists in Chile previously noted that suddenly, around 3,800 years ago, a number of coastal sites were systematically abandoned, with new sites soon appearing farther inland. Additional evidence, like shell middens that bore evidence of having been eroded by strong currents, hinted at a potential paleotsunami.<\/p>\n![\"\"](\"https:\/\/hakaimagazine.com\/wp-content\/uploads\/body-paleotsunamis-scaled.jpg\")
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