Report on Izu-Torishima (Japan) — 14 August-20 August 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 August-20 August 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Izu-Torishima (Japan). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 14 August-20 August 2002. Smithsonian Institution and US Geological Survey.
30.484°N, 140.303°E; summit elev. 394 m
All times are local (unless otherwise noted)
The eruption that began at Tori-shima on 11 August continued until at least noon on the 14th. Eruption clouds reached ~1.2 km a.s.l. on the 13th and ~1 km a.s.l. on the 14th. During observations on the 14th, scientists found smoke was being emitted from three areas on the western inner wall of the summit crater. They also found that the crater seemed to have widened during the eruption and the sea surface was no longer discolored.
Geologic Background. The circular, 2.7-km-wide island of Izu-Torishima in the southern Izu Islands is capped by an unvegetated summit cone formed during an eruption in 1939. Fresh lava flows from this eruption form part of the northern coastline of the basaltic-to-dacitic edifice. The volcano is referred to as Izu-Torishima to distinguish it from the several other Japanese island volcanoes called Torishima ("Bird Island"). The main cone is truncated by a 1.5-km-wide caldera that contains two central cones, of which 394-m-high Ioyama is the highest. Historical eruptions have also occurred from flank vents near the north coast and offshore submarine vents. A 6-8 km wide submarine caldera lies immediately to the north.