It was a great disaster during that early 90s when Mt. Pinatubo erupted to a great extent. I was a witness to that great eruption and had seen how a province was almost erased in the Philippine map.

Here's Pinatubo, peaceful and calm as it may seem.


As of the 1991, it unleashed its rage.


And one of the aftermaths, just like an unexpected white christmas.



Here's a good link for more history: http://en.wikipedia.org/wiki/Pinatubo

Yes, I've studied that eruption. It started out as Pyroclastic flows; http://en.wikipedia.org/wiki/Pyroclastic_flow
Then lahars: http://en.wikipedia.org/wiki/Lahar
If I remember correctly there is still trouble in using the land around Pinatubo.