Erik Klemetti, in his Eruptions blog, put together a really good post on the history and consequences of the eruption in the Philippeans.
The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines link is one of his suggested sites for an excellant summary, as well as this one about the Lahars that followed.
[snip]
Explosive eruptions can deposit huge amounts ash and other volcanic debris on a volcano's slopes. Lahars form when water from intense rainfall, melting snow and ice, or the sudden failure of a natural dam, mixes with this loose volcanic material, creating mudflows that can be particularly dangerous and destructive. Although lahars contain at least 40% (by weight) volcanic ash and rock fragments–making them dense and viscous like wet concrete–they actually flow faster than clear-water streams. These mudflows can rush down the flanks of a volcano at speeds as great as 40 miles (65 kilometers) per hour and can travel more than 50 miles (80 kilometers). Lahars that contain the most debris (as much as 90%) move the fastest and are the most destructive.
From the blog: The Philippine government has now decreed that June 15 will be "Pinatubo Day" to commemorate the events of 1991 and remember the over 700 people who did lose their lives in the eruption or from the lahars and disease that followed.
The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines link is one of his suggested sites for an excellant summary, as well as this one about the Lahars that followed.
[snip]
Explosive eruptions can deposit huge amounts ash and other volcanic debris on a volcano's slopes. Lahars form when water from intense rainfall, melting snow and ice, or the sudden failure of a natural dam, mixes with this loose volcanic material, creating mudflows that can be particularly dangerous and destructive. Although lahars contain at least 40% (by weight) volcanic ash and rock fragments–making them dense and viscous like wet concrete–they actually flow faster than clear-water streams. These mudflows can rush down the flanks of a volcano at speeds as great as 40 miles (65 kilometers) per hour and can travel more than 50 miles (80 kilometers). Lahars that contain the most debris (as much as 90%) move the fastest and are the most destructive.
From the blog: The Philippine government has now decreed that June 15 will be "Pinatubo Day" to commemorate the events of 1991 and remember the over 700 people who did lose their lives in the eruption or from the lahars and disease that followed.