Mount Pinatubo Revisited: A Study of Lahar Erosion

This slide shows older (at least 400 years B.P.) and recent (1991) pyroclastic flow deposits from Mt. Pinatubo. (Photograph from Mt. Pinatubo Revisited slide set)

Mount Pinatubo is located on the Island of Luzon in the Philippines, about 100 km northwest of Manila. The volcano, with K-Ar datings of approximately 1.1 million years, and with the youngest carbon-14 dating of + 400 years B.P. (before present), is the youngest volcano in the western Luzon volcanic arc.

On April 2, 1991, Pinatubo, which had been rumbling for months, stirred to life. Over the next six weeks earth tremors and minor explosions occurred. These natural warnings led to the evacuation of personnel at Clark Air Base and of 55,000 people in nearby towns and villages. At dawn on June 15, 1991, a cataclysmic eruption began with a tremendous explosion that destroyed ten deserted villages. The eruption deposited approximately 5 to 7 km3 of volcanic fragments in pyroclastic flows on the slopes of the volcano and over neighboring towns and agricultural areas. It is this material that continues to threaten structures and lives in the area, in the form of lahars (debris flows) during heavy rainstorms.

This slide set presents images and discusses the threat from the Mt. Pinatubo deposits. View the slides online.

Additional background information on Mount Pinatubo.

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