A mass of marine debris found in a Hawaii sinkhole suggests a monster tsunami once hit the island, and this type of devastating event could happen again.
Scientists believed a wall of water about 30 feet high smashed into the shores of Hawaii 500 years ago following a 9.0-magnitude earthquake off the coast of the Aleutian Islands, the Amercan Geophysical Union reported. The wave would have been three times bigger than the 1946 tsunami, which was the largest in Hawaii's memorable history.
Although an earthquake large enough to trigger this kind of event only happens about once every 1,000 years, the finding has inspired Hawaii officials to take a closer look at evacuation strategies. Newly proposed maps would double the extent of evacuation regions; the officials hope to have these new maps distributed by the end of the year.
"You're going to have great earthquakes on planet Earth, and you're going to have great tsunamis," said Rhett Butler, a geophysicist at the University of Hawaii at Manoa and lead author of the new study published online in Geophysical Research Letters, a journal of the American Geophysical Union. "People have to at least appreciate that the possibility is there."
To make their findings the researchers conducted a wave model to predict how a tsunami would flood the Kauai coastline. They also used radiocarbon dating on marine deposits from Sedanka Island off the coast of Alaska and along the west coasts of Canada and the United States to show the debris could have all come from a tsunami that occurred during the same time period.
"[The authors] stitched together geological evidence, anthropological information as well as geophysical modeling to put together this story that is tantalizing for a geologist but it's frightening for people in Hawaii," said Robert Witter, a geologist at the U.S. Geological Survey in Anchorage, Alaska who was not involved in the study.
Witter doesn't believe the evidence can conclude the tsunami hit all of the continents in question based on radiocarbon dating alone. This technique can determine approximately how old an object (or mass of sediment) is, but the events could have occurred hundreds of years apart.
"An important next thing to do is to look for evidence for tsunamis elsewhere in the Hawaiian island chain," Witter said.
