MANILA, PHILIPPINES. June 15, 1996. Five years ago today, Mount Pinatubo blew its stack, and the island of Luzon — and the entire world — is still suffering from the aftereffects.

The ash cloud created by the eruption has circled the globe several times. Some 20 million tons of sulfur dioxide contained in this cloud have been injected into the stratosphere, and it was estimated that global temperatures dropped about half degree Celsius between 1991 and 1993.

A bit over a year after Pinatubo erupted, a lava dome began to build up in the new caldera. Fresh magma rose from far below the mountain, and the volcano erupted again, but not as violently. Heavy rains that fell during the 1994 monsoon season triggered numerous lahars, which again devastated the region.

The pyroclastic flows that filled up valleys have kept much of their heat over the years. Temperatures, as high as 900 degrees Fahrenheit (500 degrees Celsius), are still being recorded, and this heat may be retained for decades! When water from streams or underground seepage comes into contact with the hot deposits, it often explodes and sends more ash down on the countryside. Rice paddies and sugarcane fields that weren't burned in the eruption have recovered, but those buried under lava flows and lahars will be unproductive for years to come. Despite all the destruction, some of the volcanic materials have seeped into the surrounding soil, enriching it with their nutrients. The grandchildren and great-grandchildren of today's islanders will inherit revitalized land.

Review Questions

1. Fertilization of soil is a long-term effect to the _________ caused by volcanic eruptions.

a. lithosphere
b. hydrosphere
c. biosphere
d. atmosphere

2. Describe one way in which the atmosphere may impact the lithosphere after a volcanic eruption.

3. True or False: The eruption of Mount Pinatubo has only affected the island of Luzon. Provide reasons for your answer.