Report on Marapi (Indonesia) — August 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 8 (August 1999)
Managing Editor: Richard Wunderman.
Marapi (Indonesia) Strong explosions within moderate background activity during June-September
Please cite this report as:
Global Volcanism Program, 1999. Report on Marapi (Indonesia). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 24:8. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN199908-261140.
0.381°S, 100.473°E; summit elev. 2891 m
All times are local (unless otherwise noted)
Moderate eruptive activity at Marapi during June-September was interrupted by a few isolated powerful explosions. On 1 June a loud detonation was heard and earthquakes were felt in Bukittinggi village near the volcano. These phenomena were followed by an outpouring of thick dark ash from the crater forming a billowing cloud reaching 3,200 m above the summit. Events soon returned to more typical emissions of white or gray ash rising a few hundred meters and not accompanied by detonations. During 3-9 August white and sometimes black ash plumes reached 200-1,200 m above the peak. There were also increases in the number of volcanic and small explosive seismic events recorded that week.
J. Bardintzeff reported that at 0720 on 5 August a violent explosion sent an ash column, at first black but later gray in color, ~1,000 m above the summit. Fine ash fell at distances of up to 1 km E of the volcano at 0745. Two groups of people were standing near the crater at the time of the explosion. A group near the west side was safe, but three people of another group standing at the eastern crater rim were injured. Witnessed said that they were knocked down by the force of the explosion in which several 10-cm-diameter bombs were ejected. The injuries included cuts from debris and burns about the face, head, arms, and hands. Several people have been killed or injured at Marapi during the past ten years.
Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2000 m above the Bukittinggi plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.
Information Contacts: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Jacques-Marie Bardintzeff, Laboratoire de Petrographie-Volcanologie, bat 504, Universite Paris-Sud, 91405, Orsay, France (Email: firstname.lastname@example.org).