GEOLOGIC HISTORY
Semeru is located ~40 km SE of the city of Malang.
Semeru, the highest volcano on Java, and one of its most
active, lies at the southern end of a volcanic massif
extending north to the Tengger caldera. The steep-sided
volcano, also referred to as Mahameru (Great Mountain),
rises abruptly to 3,676 m above coastal plains to the south.
Gunung Semeru was constructed south of the overlapping
Ajek-ajek and Jambangan calderas. A line of lake-filled
maars was constructed along a N-S line cutting through the
summit, and cinder cones and lava domes occupy the eastern
and NE flanks. Summit topography is complicated by the
shifting of craters from NW to SE. Frequent 19th and 20th
century eruptions were dominated by small-to-moderate
explosions from the summit crater, with occasional lava
flows and larger explosive eruptions accompanied by
pyroclastic flows that have reached the lower flanks of the
volcano. Semeru has been in almost continuous eruption since
1967.
Historic Activity:
- Nearly 60 eruptions have occurred from 1818 to
1964.
- The first reported historical eruption was in
1818.
- Frequent small-to-moderate Vulcanian eruptions have
accompanied lava dome extrusion since 1967, and periodic
pyroclastic flows and lahars have damaged villages below
the volcano. Strombolian activity, lava flows, and
eruption plumes rising 400-600 m have also occurred since
the current activity began in 1967.
- A major secondary lahar on May 14, 1981 caused
>250 deaths and damaged 16 villages.
Recent Activity:
- Explosions ended on July 1990 and a large collapse
pit in the crater formerly occupied by the lava dome was
observed. Eruptive activity and the number of explosion
earthquakes sharply decreased from the beginning of May
to December 1990.
- In February 1991 a lava flow traveled 400 m from the
crater. Explosions continued through April 1991.
Increased frequency of explosions and tremor began in
Dec. 1991. Explosions from the Jonggring Seloko crater
were continuing during a visit on Oct. 22, 1992.
- Visual and seismic activity increased in late 1993,
with frequent collapses from the summit lava flow.
Volcanic earthquakes were recorded since October, and
peaked on Dec. 25, 1993. Continuous tremor was recorded
from Jan. 26, 1994 to Feb. 3 when lava avalanches and
pyroclastic flows from the summit crater descended SE
along the Kembar and Kobokan rivers, reaching 7.5 km and
11.5 km from the summit, respectively. Volcanic materials
also entered Sumbersari village, located between the
rivers, and killed 6 people. From Feb. to Aug. 1994,
explosions generated small ash clouds upto 500 m above
the summit.
- Activity from the Jonggring Seloko summit crater
continued in January and February 1995. Ash eruptions
rose as high as 600 m above the summit. Lava avalanches
increased in frequency and glow was sometimes observed
the summit. Increasing seismicity, avalanches, and
pyroclastic flows began in early June. Significant
pyroclastic flows ocurred in late July continued into
Dec.
- Airline report of eruption on May 5, 1996. Eruption
plume to 10.5 km altitude. Other airline reports on May
7, May 11 and May 12.
- Ongoing eruptive activity thru 2000.
- Ongoing eruptive activity thru Oct. 2001
Data Sources
- Smithsonian's SEAN Bulletin (V. 1, No. 14 to V. 14,
No. 7)
- Global Volcanism Network (V. 15, No. 7 to V. 26, No.
8).
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