Report on Miyakejima (Japan) — 8 December-14 December 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 December-14 December 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Miyakejima (Japan). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 8 December-14 December 2004. Smithsonian Institution and US Geological Survey.
34.094°N, 139.526°E; summit elev. 775 m
All times are local (unless otherwise noted)
According to the Geological Survey of Japan, volcanic activity at Miyake-jima that began during the summer of 2000 continued through early December. The sulfur-dioxide flux remained high through November 2004, with 3,000-10,000 tons emitted per day. The flux seemed to remain constant since October 2002. On 30 November a minor eruption occurred after a 2-year lull. Several minor eruptions followed, with the most recent eruption occurring on 9 December.
Geologic Background. The circular, 8-km-wide island of Miyakejima forms a low-angle stratovolcano that rises about 1100 m from the sea floor in the northern Izu Islands about 200 km SSW of Tokyo. The basaltic volcano is truncated by small summit calderas, one of which, 3.5 km wide, was formed during a major eruption about 2500 years ago. Parasitic craters and vents, including maars near the coast and radially oriented fissure vents, dot the flanks of the volcano. Frequent historical eruptions have occurred since 1085 CE at vents ranging from the summit to below sea level, causing much damage on this small populated island. After a three-century-long hiatus ending in 1469, activity has been dominated by flank fissure eruptions sometimes accompanied by minor summit eruptions. A 1.6-km-wide summit caldera was slowly formed by subsidence during an eruption in 2000; by October of that year the crater floor had dropped to only 230 m above sea level.
Source: Geological Survey of Japan