Scientists found a cave in Indonesia that has evidences of ancient tsunamis as old as 7,500 years old. They believe that this discovery can help better explain the formation of these damaging waves and probably predict its next occurrence.
In December 26, 2004, an undersea earthquake occurred in the west center coast of Sumatra, Indonesia. With a magnitude of 9.1-9.3, it became the third largest earthquake recorded and the longest as well, lasting up to 10 minutes. It was so strong that its vibration extended to Alaska and resulted to a massive tsunami. It killed over 230,000 people in 14 countries affected.
Charles Rubin, lead researcher from the Earth Observatory of Singapore, and his colleagues accidentally discovered the Indonesian cave while doing another research in the area. They found the limestone cave a hundred meters away from Banda Aceh, a province greatly affected by the tsunami.
They began analyzing the sand deposits in the cave which were carried by the waves. They used radiocarbon analysis to identify the age of the sand, the clam shells, and other microscopic organisms found within the cave.
Their analysis revealed that there were 11 different traces of sands brought by tsunami waves before 2004. The last one before 2004 was 2,800 years ago. Further analysis revealed that there were still four more that occurred every 500 years before the 2,800-year mark. Their next step is to study the height of the tsunami waves that passed into the cave thousands of years ago.
Though it may seem that a tsunami happens every 500 years, the researchers clarified that they will need further study to prove that.
“The take-home message is perhaps that the 2004 event doesn’t mean it won’t happen for another 500 years,” Rubin told the Science Recorder. “We did see them clustered together in time. I wouldn’t put out a warning that we’re going to have an earthquake, but it shows that the timing is really variable.”
The study was presented at an American Geophysical Union conference in San Francisco, Calif.
