Merapi, Java, Indonesia

ERUPTIVE HISTORY

Location: 7.5S, 110.4E
Elevation: 9,548 feet (2,911 m)
Last Updated: July 17, 2005

Merapi stratovolcano in central Java is capped by an unvegetated, growing lava-dome complex. Merapi is one of Indonesia's most active volcanoes. Periodic collapse of its growing lava dome has produced pyroclastic flows and lahars that have devastated populated areas below the volcano.
Photo by Yustinus Sulistiyo, 1994 (Volcanological Survey of Indonesia).

Like most of the volcanoes in Indonesia, Merapi is stratovolcano. It is tall (2.8 km or 1.7 miles high) and has steep slopes. The top of the volcano sometimes has a normal crater, but usually a broad mound of pasty lava -- called a dome -- fills the crater. The dome plugs up the volcano, making it difficult for other lava and ash to escape. A broad gouge funnels lava and ash flows from the top of Merapi to the south slopes of the volcano. The top of the mountain has no vegetation because erupted ash often falls there. Dense vegetation covers the flanks of the volcano. Many farmers live in villages around the volcano. The volcanic ash makes rich soil for growing crops, but it is a dangerous place to live.

Photo by Jack Lockwood,
U.S. Geological Survey, September 6, 1982.

Photograph by Robert Koyanagi,
U.S. Geological Survey, July 28, 1979.

Merapi is located ~30 km immediately north of Yogyakarta, a city with a population of 500,000. Merapi has the unfortunate distinction of producing more nuee ardentes than any other volcano on Earth. The nuee ardentes result from collapse of the lava dome at the summit. Of the 67 historic eruptions 32 have had nuee ardentes associated with them. Eleven of these eruptions resulted in fatalities. Merapi is closely monitored by the Volcanological Survey of Indonesia. Shortly before the Koyanagi photograph below was taken, Merapi was generating up to 40 nuee ardentes per day.

Rockfall from the collapse of a lava dome.
Photo by Jack Lockwood, U.S. Geological Survey, September 8, 1982.

Merapi is a stratovolcano in central Java. Merapi has had 68 historic eruption since 1548. The current eruption began in 1987. Because of Merapi's violent past and its close proximity to Yogyakarta it was designated a Decade Volcano and is the target of increased research efforts.

Lava dome at the summit of Merapi. During 1982, the lava dome was growing about 80,000-100,000 cubic meters per month. The dome collapsed in late November, creating nuee ardentes. Photo by Jack Lockwood, U.S. Geological Survey, October 17, 1982.

Like all volcanoes, Merapi has eruptions of different sizes. Small eruptions happen every 2-3 years, bigger ones every 10-15 years, and very large ones every 50-60 years. The biggest eruptions occurred in the years 1006, 1786, 1822, 1872 and 1930. The eruption of 1006 spread ash all over the central part of the island of Java. Here is a graph that shows how many eruptions of Merapi are known during the last 500 years.

QUESTIONS:

What can you say about the number of reported eruptions over the last five centuries?
What might be the causes for the great increase in the number of reported eruptions of the last two centuries compared to the earlier three?

Answers to questions

Pyroclastic flow deposit on Merapi.
Photo by Jack Lockwood, U.S. Geological Survey, November 2, 1982.

Kadong school is in the lower left of this photo. Barriers (just left of the stream valley) have protected the school from lahars. In 1979, heavy rainfall mobilized old lahar deposits to create landslides that travelled as far as 12 miles (20 km) downslope. Eighty people were killed.
Photo by Jack Lockwood, U.S. Geological Survey, September 26, 1982.

In late November of 1994, collapse of a lava dome at Merapi generated pyroclastic flows and surges that travelled as far as 5 miles (7.5 km) from the summit. The flows and surges killed 43 people. The plume associated with the dome collapse rose 6 miles (10 km) above the volcano. Over 6,000 people were evacuated.

Click here for more information on Merapi Hazards

Click here for Virtual Tour of Merapi

Additional Sources of Information:

Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.

Smithsonian Institution's Global Volcanism Program



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