These data indicate the likelihood of new powerful tsunamis in the region.
Tsunamis are long and high waves that are most often caused by powerful underwater earthquakes. Unlike surface storm waves, the entire water column moves during a tsunami. These waves come unexpectedly and can cover several kilometers inland. This is associated with a large number of victims: for example, as a result of the 2004 underwater earthquake in the Indian Ocean, from 230 to 280 thousand people died.
In a coastal cave in western Sumatra, scientists have discovered intact sediments left behind by several tsunamis between 2,900 and 7,900 years ago. According to scientists, the younger layers were "erased" by a powerful wave during the 2004 earthquake, which largely destroyed the neighboring town of Banda Aceh. The age of the deposits, consisting of sand brought by the tsunami and organic materials, was made possible by radiocarbon analysis of rock sections.
Stratigraphic section of the cave, dark layers - organic deposits, Earth Observatory of Singapore
The section clearly shows two types of sediment layers: sandy and organic (eg bat excrement). Their alternation made it possible to identify and date 11 tsunamis that occurred over five thousand years. Scientists have discovered periods of tsunami activity, when up to four earthquakes could occur over a century. A period of calm was also identified, when relative calm reigned off the coast of Sumatra. Then for two thousand years there was not a single tsunami in the territory. The “rhythm” of earthquakes looks like this: after a series of small tsunamis, there is a long-term calm, followed by a strong wave, such as in December 2004.
These data suggest that several more earthquakes may occur in the Indian Ocean in the coming decades, followed by a tsunami.
The article was published in the journal Nature Communications.
Natalia Pelezneva
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