The plume from Pinatubo was 26 miles high.
I remember it vividly - it passed over Saudi Arabia just about the same time the smoke from the Kuwait oil fires did.
It was an incredible "other-wordly" cast over that part of the world.
Actually reminded me of the end of the world.
The PBS show Nova did an episode on that eruption-they had a crew with the USGS guys who showed up when it started rumbling and advised the military on when to evacuate.
The video they got of the eruption was awesome