The world's largest volcano, Tamu Massif, is located underwater, approximately 1,000 miles east of Japan.
World's largest volcano discovered off the coast of Japan. The volcano is roughly the size of New Mexico. Volcanologists had warned that a “lava dome” was growing inside the volcano’s crater, although it was uncertain when or if the volcano would erupt. Tamu Massif is as big as the British isles and was formed roughly 145 million years ago Sunday’s eruption, which was the biggest volcanic activity in Shinmoedake in 52 years, caused widespread destruction and panic.