(CNN) - Scientists have discovered one of the largest volcanoes in the solar system.
Researchers from Texas A & M University and the University of Houston found the volcano, named Tamu Massif, at the floor of the Pacific Ocean, about a thousand miles east of Japan.
It covers 120,000 square miles, an area about the size of New Mexico.
The 145-million-year-old volcano is no longer active, which may explain why it was previously unknown to science.
Earth's largest active volcano is Mauna Loa, in Hawaii, which covers about 2,000 square miles, though most of that is below sea level.