Izu-Tobu (伊豆東部火山群 Izu Tōbu Kazangun) is a large, dominantly basaltic, range of volcanic on the east side of the Izu Peninsula in Japan. The field covers a total area of 400 km2. The only recorded activity was a submarine phreatic eruption, between the city Ito and Hatsushima island, that lasted for just 10 minutes. Ito, home to 74,000 people, is known for its hot springs.