JCG-discovered “Godzilla” seafloor formation wins heritage status

The Japan Coast Guard said that the “Godzilla Megamullion,” a massive seafloor formation discovered during its 2001 continental shelf survey, has been selected for the International Union of Geological Sciences’ list of 100 Geological Heritage Sites.

The JCG announced the designation of the megamullion, located southeast of the remote Tokyo-administered Pacific island of Okinotorishima, on Friday.

A megamullion is a dome-shaped seafloor structure formed when mantle rocks are exposed on the ocean floor through fault activity associated with seafloor spreading.

Located on the Philippine Sea plate, the Godzilla Megamullion measures about 125 kilometers in length and 55 kilometers in width, making it roughly 10 times larger than a typical megamullion. It is believed to be the largest such formation ever discovered.

An overview of the underwater geological formation known as “Godzilla Megamullion” | JAPAN COAST GUARD / VIA JIJI

The megamullion was named after the giant monster Godzilla because of its enormous size and was registered internationally under that name in 2021.

Studies of the Godzilla Megamullion conducted by an international team led by Japanese scientists have produced important findings on mantle structure and the processes involved in plate formation. The site was recognized as a globally significant geological reference point for scientific research, according to the JCG.

This marks the third round of selections for the IUGS geological heritage list. Other Japanese sites previously chosen include the Nojima Fault in Hyogo Prefecture, which triggered the 1995 Great Hanshin Earthquake.