Tsunami in the Philippines (World Tsunami Awareness Day)
Today is #WorldTsunamiAwarenessDay.
A tsunami is a series of large waves brought about by sudden violent movements in the ocean. On any given day, the ocean typically has waves, but these waves are only wind-generated waves. A tsunami wave is usually caused by earthquakes or other events like ocean floor landslides, volcanic eruptions, or a meteoric impact.
In the Philippines, the worst tsunami event in history is the 1976 Moro Gulf Tsunami in Western Mindanao. The tsunami devastated the coastal provinces bordering the Moro Gulf and the northern Celebes Sea. Tsunami waves were reported to be as high as 9 meters in Lebak, Sultan Kudarat. This tsunami was caused by a magnitude 7.9 earthquake with an epicenter about 96 km off the coast of Cotabato. This tragic tsunami happened just after midnight when most people were already asleep.
Follow the link to learn more about tsunamis: https://bit.ly/3bvSXKu
Geologic evidence of tsunamis, although quite difficult to interpret and establish, is still present. A recently published study by the National Institute of Geological Sciences in UP Diliman documents the evidence of a potential tsunami deposit of the 1976 Moro Gulf Tsunami. The possible geologic evidence of the event was observed in a mangrove swamp and a coastal plain in western Mindanao. The preserved wash-over deposits from the observed study areas are characterized by a predominantly coarse sand-sized sediment with mud rip-up clasts, magnetite, and lamina. The base of the deposited layer is reportedly erosive in many of the observed deposits.
The geological evidence of a modern or a prehistoric tsunami offers a more thorough understanding of these extreme wave events. In a country frequented by earthquakes, this new information could be utilized for a better prepared community against tsunami threats.
Click here to read the full paper: https://doi.org/10.1016/j.margeo.2021.106535
Text and image by the NMP Geology and Paleontology Division
© National Museum of the Philippines (2021)