Scientists Discover Dinosaur-Era Sea Swallowed Up By Tectonic Plates

Scientists discovered a buried tectonic plate that revealed an ancient dinosaur-era sea.

Underneath the Philippine Sea is a seafloor formed by the 50-million-year-old Philippine Sea tectonic plate. To study the plate, geoscientists used images created from earthquake data and developed new methods to reconstruct the plate's history. This led the researchers to identify the previously unknown East Asian Sea Plate, where an ancient sea as old as the post-dinosaur era used to exist.

The Philippine Sea lies in a region where three major tectonic plates converge: the Pacific, Indo-Australian and Eurasian plates. These plates are bordered by smaller plates, which includes the Philippine Sea Plate.

 Scientists have previously agreed that the plate is 55 million years old, but they found it difficult to determine its size, orientation and path as it had been migrating northwest.

In a study published in the Journal of Geophysical Research: Solid Earth, the scientists detailed their methods and their findings. The team reconstructed the movements of 28 slabs of tectonic plate segments through a new imaging technique called seismic tomography, EOS reports. The method makes use of earthquake waves and multiple monitoring stations to find out how fast the waves travel through the Earth.

Through this method, the researchers were able to uncover the plates' historical movements and determine their positions before they sank. The scientists found sunken slabs under East Asia of about 70 million square kilometers. They also discovered that over 15 million square kilometers of the sunken plate used to form the seafloor of an ancient sea that lay between the Pacific Ocean and the Indian Ocean, which scientists hypothesized as the "East Asian Sea." According to the researchers, the sea would have existed 52 million years ago, just after dinosaurs went extinct and new life forms inhabited the Earth.

According to the researchers, the sea gradually shrank as the Philippine Sea plate migrated northwest, subducting the northern portion of the East Asian Sea plate. The southern area of the East Asian Sea plate was also subducted by other neighboring plates.

"East Asia has been a place where plates have been coming together, converging and disappearing from the Earth's surface in a process called subduction," Jonny Wu, a geologist at the University of Houston and lead author of the study, said in a statement.

"Because the information you're looking for to piece together the history of the area is actually disappearing from the Earth's surface, it's made it very difficult."

The study is also a step toward a more technical method of interpreting models based on earthquake data, said geoscientist Hans-Peter Bunge from the Ludwig Maximilians University in Munich, who was not involved in the study.

According to the researchers, they will be using the new technique for future studies. "As we keep working in other areas with a lot of unknowns - for example, South America or the Himalayas - we'll continue to test these methods and refine them, and hopefully contribute new ideas to Earth science," Wu said.