Anyway we went outside onto a ramp that was in effect a giant concrete boat launch into a large calm river pool. The teacher pointed out to someone in the class that there was a rapidly changing steam/smoke cloud billowing up from the water at the end of the ramp. He said that we were lucky to see such a thing and called it by some large scientific name. My gut called it magma.
It was at that point that I noticed that the ramp was getting hotter and starting to glow a bit at the bottom and move up. It was odd because what appeared to be rivets in the concrete started to glow first. I tried to warn people but nobody would even listen to me. Finally I stuck my knife in the ground and it came back molten they started listening to me. By that time the hill to the lower right of us had become completely consumed by molten rock.
Then I remember running and climbing people's roofs to connect a device with a headset that allowed me to make calls to warn them about the disaster and keep tabs on it. I got caught by one old man and his family and had to apologize. That assuaged him and his family and I spent dinner with them.
Then I was back at the High School with the rest of the class but we'd convinced the Dean to make an announcement concerning the disaster. The walls started shaking and the building started to collapse.
Suddenly I found myself in a car driving far away. I stopped in a tiny little town where the restaurant was also the local police station. I recall that I had stopped to get something to eat and pick up my mail. I told the waitress that there was a disaster coming this way and that they should get out. I pointed out the large purple funnel cloud a few miles away coming this direction. I told her "You don't even have time to mail the bills." which made perfect sense at the time but makes no sense now. It was then that I ran out to go to my car but it wasn't there. The disaster funnel was really close. It was that time that I "woke up" in the dream and realized that it was a nightmare that I wanted out of. I did the mental effect of bouncing my head into my pillow and kept telling myself "I know I'm dreaming! Wake UP!" I repeated that and eventually I woke up for real in my bed.