Toya (Japan)

Status Unknown Eruption 2001 733m
Stratovolcano (Subduction zone / Continental crust (> 25 km))

Usuzan, 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 Nakajima, a group of forested Pleistocene andesitic lava domes. The summit of the basaltic-to-andesitic edifice of Usu is cut by a somma formed about 20-30,000 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 Showashinzan, 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 Showashinzan from 1943-45 was painstakingly documented by the local postmaster, who created the first detailed record of growth of a lava dome.

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.

Copyrighted photo by Dick Stoiber, 1981 (Dartmouth College).

Last updated 2019-08-04 00:28:03