Usu volcano, Japan

Usu volcano is a small stratovolcano located astride the southern topographic rim of the 110,000-year-old Toya caldera.

The summit of the volcano, seen here above the town of Toyako-Onsen to its NW, consists of dacitic lava domes and a cryptodome that were emplaced in a small summit caldera during historical eruptions, most recently during 1977-82.

Similar historical eruptions have occurred on the flanks.

Usu, one of Hokkaido's most well-known volcanoes, is a small stratovolcano located astride the southern topographic rim of the 110,000-year-old Toya caldera.

The center of the 10-km-wide, lake-filled caldera contains Naka-jima, a group of forested andesitic lava domes.

The summit of the basaltic-to-andesitic edifice of Usu is cut by a somma formed about 7-8,000 years ago when collapse of the volcano produced a debris avalanche that reached the sea.

Dacitic domes erupted along two NW-SE-trending lines fill and flank the summit caldera.

Three of these domes, O-Usu, Ko-Usu and Showa-Shinzan, along with seven crypto-domes, were erupted during historical time.

The 1663 eruption of Usu was one of the largest in Hokkaido during historical time.

The war-time growth of Showa-Shinzan from 1943-45 was painstakingly documented by the local postmaster, who created the first detailed record of growth of a lava dome.

PHOTO SOURCE: Copyrighted photo by Dick Stoiber, 1981 (Dartmouth College) courtesy of the Global Volcanism Program, Smithsonian National Museum of Natural History, used with permission.

---

NOTE: The information regarding Volcano on this page is re-published from other sources.

No claims are made regarding the accuracy of Volcano information contained here.

All suggestions for corrections of any errors about Volcano photos should be addressed to the copyright owner noted below the photo.