Hazards of Merapi

The island of Java has more than 600 people per square km, one of the highest population densities in the world. Yogyakarta city, with a population of 3 million, is 15 miles (25 km) south of Merapi. About 70,000 people live in the immediate vicinity of the volcano. Merapi is a basaltic to basaltic-andesite stratovolcano with a summit crater containing an unstable lava dome. Merapi is Indonesia's most active volcano and well known for partial collapse of lava domes and the generation of pyroclastic flows. Pyroclastic flows can travel as far as 8 miles (13 km) from the summit and reach speeds of 70 mph (110 km/hr). Pyroclastic flow deposits can be remobilized as lahars. Direct observations of Merapi have been recorded since 1888. Recent study of tephra deposits on the flanks of the volcano found 27 marker beds that reveal Merapi's past history. The volcano has had numerous moderate to large (1 million cubic m) eruptions. These eruptions typically begin with pyroclastic flows and are followed by widespread pyroclastic air fall. Plinian to subplinian eruptions are common. These older deposits indicate that Merapi is capable of eruption styles very different from those currently observed.

Distance traveled by volcanic materials on the southwest flank of Merapi. From Suryo and Clarke (1985).

Volcanic hazard map for Merapi volcano from Suryo and Clarke (1985).

Photo of three-dimensional hazard map of Merapi volcano. Courtesy of the Volcanological Technology Research Center (formerly the Merapi Volcano Observatory).

Sources of Information:

Andreastuti, S.D., Alloway, B.V., and Smith, I.E.M., 1997, A detailed tephrostratigraphy at Merapi volcano, central Java: Implication for eeruption prediction and hazard assessment, in Program and Abstract, 2nd Merapi Decade Volcano International Workshop, Yogyakarta, VSI-UNESCO, p. 26.

Purbawinata, M.A., Ratdomopurbo, A., Sinulingga, I.K., Sumarti, S., Suharno, 1996, Merapi volcano a guide book: Volcanological Survey of Indonesia, Bandung, 64 p.

Suryo, I. and Clarke, M.C.G., 1985, The occurrence and mitigation of volcanic hazards in Indonesia as exemplified at the Mount Merapi, Mount Kelut, and Mount Galunggung volcanoes: Q.J. Eng. Geol. London, v. 185, p. 79-98.

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