LEDC Natural Hazard Case Study :

Mount Pinatubo (the Philippines - 1991)

Mount Pinatubo in the Philippines had lain dormant for 600 years - it had last erupted in 1380. But in June 1991 it finally erupted to the surprise of scientists, becoming one of the three largest eruptions of this century.

the Philippines lie on a destructive plate boundary, where the Philippines Plate, composed of oceanic crust moves in a north-westerly direction towards the Eurasian Plate. When they meet, the Philippines Plate is forced to dip down steeply under the Eurasian Plate. The oceanic plate is turned into magma, rises and erupts on the surface. Even before Pinatubo's eruption, there were already 30 active volcanoes across the Philippines's many islands.

There were several advance warnings of a possible eruption, and minor eruptions started from the 9th June, but the major eruption was on the 12th. An explosion sent a cloud of steam and ash 30km into the sky. Layers of up to 50cm fell on local farmland, villages and towns. The ash reached a 600km radius, some as far away as Australia. The eruptions continued for several days, accompanied by earthquakes, torrential rain and mud. The weight of the ash caused 2 000 000 homes to collapse, as well as a hospital, schools and factories. Power supplies were cut for 3 weeks and water supplies contaminated. Roads were unusable and bridges destroyed, making relief operations all the more difficult.

More long-term, the thick layer of ash ruined the rice harvests of both 1991 and 1992. More than 1 million farm animals died through starvation or drinking contaminated water. Hundreds of people were forced to seek shelter and food in the cities. Huge shanty camps were set up, but were soon rife with disease. The monsoon rains caused flooding and mud-flows. The ash from the eruption blocked some of the heat from the Sun, lowering world temperatures. Scientists believe this may have slightly slowed global warming.

In total 700 lost their lives either directly or indirectly because of the eruption.