FIRE and MUD: Eruptions and Lahars of Mount Pinatubo, Philippines


When Pinatubo was threatening to erupt, reports of effects and recovery strategies from eruptions elsewhere in the world were a useful starting point for contingency planning; after the eruption, the demand for such reports rose sharply. A full account of the effects of the Pinatubo eruption is beyond the scope of this volume but would be valuable for future workers.

For now, an overview of impacts, with special emphasis on people, is told compellingly by C.B. Bautista in the introductory section. Starting in 1991, the Pinatubo story has been a saga of massive evacuations (at times, reaching more than 200,000 persons), massive multiyear dislocations (as of 1993, more than 50,000 persons), and extensive damage to towns, infrastructure, and farms. Initially, the indigenous Aeta population was hit hardest; later, they were joined by an even greater number of lowlanders, routed from their homes and land by lahars. Substantial social changes are underway--some temporary, some irreversible and permanent.

Impacts on buildings, described by Spence and others, were unusually serious because the ash was wet (from typhoon rains) and therefore heavier than it would have otherwise been. Impacts of ash on industries, health, and agriculture are topics for future discussion by others.

Economic impacts of the eruption and lahars are described by Mercado and others, who see a serious but temporary interruption in the economy. Immediate impacts such as loss of income from agriculture and from the U.S. bases are expected to diminish as crops recover and new industry fills the former military bases. Investor confidence and regional infrastructure are also expected to recover.

Hot cars

"Hot cars" on Clark Air Base, blanketed by tephra and washed by torrents of water and debris that overflowed storm drains.

One unusually wide-reaching impact was that to jet aircraft (Casadevall and others). Commercial and military aircraft in the Philippines were generally alerted to the potential for adverse effects from ash and were accordingly moved out of the way or diverted in flight before the main eruption. However, a number of commercial jet aircraft flying across Southeast Asia either failed to receive or ignored warnings of the approaching ash cloud and suffered substantial damage. Fortunately, no crash resulted. These impacts came virtually on the eve of a scheduled symposium in Seattle, led in part by the USGS, to detail and publicize the potential hazards of ash to aircraft and to stimulate constructive protective measures. Registration for the symposium was good before Pinatubo but jumped even higher as soon as the aviation community learned of encounters with Pinatubo ash.

The last paper in the volume (Self and others) reviews even farther reaching impacts on the global atmosphere. Atmospheric scientists have mobilized in force to quantify and track the unusual "tracer" signal from Pinatubo (including sulfate aerosol, of interest for questions of climate change). Self and others' paper offers a bridge from this geological collection to the extensive atmospheric sciences literature on Pinatubo impacts.

Buried schools

Two generations of schools at Santa Barbara, Bacolor. The older is buried in 1991 lahar deposits; the younger was built in 1992.

Kids atop school

School is out: kids atop lahar-buried school in Bamban.

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Last updated 06.02.99