Scientists on board the Kexue (Science) scientific ship said Monday that the Caroline Seamount in the west of the Pacific Ocean was an island a long time ago, after 10 days of research.
As part of the Caroline Ridge in the Pacific Ocean, the Caroline Seamount locates in the south of the Mariana Trench, the deepest spot on the Earth. The seamount had never been explored before the investigation carried out by Kexue.
"We saw many sea caves in the upper half of the seamount in the videos that a remote operated vehicle (ROV) took. It's known that sea caves take shapes in hitting by sea waves, so we believe that this seamount was an island a long time ago," said Xu Kuidong, the chief scientist on board the ship.
The island sank gradually and became a seamount below the sea surface, as it is near the junction of the Pacific Plate and the Eurasian Plate which collide with each other, the scientists said.
In the upper half of the seamount, there are stoned coral reefs which can only be seen in offshore areas, which is evidence that this seamount was an island, Xu said.
It is believed that seamounts are rich in biological diversity, but scientists saw few creatures in the west side the Caroline Seamount.
So there could be frequent landslips in the west side of the seamount, when two plates collide with each other, the scientists said.
A seamount is a mountain rising from the ocean seafloor that does not reach the water's surface, and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that have risen abruptly and are usually found rising from the seafloor to 1,000 to 4,000 meters in height.
More than 30,000 seamounts have been mapped on the Earth, but less than 10 percent of them have been studied in detail by scientists.