Japan's seafloor 'Godzilla' is now one of the world's 100 top geological sites

Godzilla has just gone global, and this time it's a rock. The Godzilla Megamullion, a giant dome on the seabed surveyed by the Japan Coast Guard, was named on 6 November one of the world's 100 Geological Heritage Sites.

The list comes from the International Union of Geological Sciences (IUGS), a body of geologists. It's the first marine pick in this category to be recognised for its scientific value in explaining how the Earth is built.

What is a megamullion? 🌊

A megamullion is a dome-shaped rise on the seafloor. It forms when the mantle, the layer beneath the ocean plate, is exposed at the seabed. According to the Coast Guard, large-scale vertical faulting shapes it.

The Godzilla Megamullion sits in international waters on the Philippine Sea Plate, about 2,000 km south of Tokyo. It measures 125 km by 55 km, roughly three times the area of Tokyo Metropolis. That makes it the largest megamullion on Earth.

Don't expect a monster-shaped outline. It was named for its sheer size, not its looks.

Why does it matter?

The IUGS picks 100 sites every two years. They're places of international importance for understanding how our planet came to be. Japan already has some, including Genbudo in Hyogo Prefecture, where the reversal of Earth's magnetic field was discovered, and the Nojima Fault, also in Hyogo, which was the source of the 1995 Great Hanshin-Awaji Earthquake.

Research teams from around the world are studying Godzilla Megamullion. Their findings include insights into how the Philippine Sea Plate formed, and that scientific value is what earned the recognition.

How did we get here?

A Japanese government survey discovered the feature in 2001. In 2022, an international committee formally approved the name for the seafloor feature, and it now appears on nautical charts and in research papers.

So a deep-sea dome that few people will ever see now sits alongside some of the planet's most important geological landmarks.