When I was six or seven, I read the Pompeii issue of National Geographic and became convinced that volcanoes were going to get me when I slept, though we lived nowhere near any. In fact, they were waiting outside my window, though if I looked outside they'd duck around back so I couldn't see them. A bad dream about fire or lava traveling along our fence up to the house was the kicker, and I remember I took the magazine outside and left it there at some point so it got ruined by rain. I was so worried about a friend who was going on a vacation to Washington because of Mt. Saint Helens, too.
My defenses against the volcanoes were always sleeping with my comforter over me, even in summer, and sleeping with a huge stuffed dog that would shoot... something, I guess... out of its nose to keep the volcanoes away. The habit of sleeping with the comforter always on lasted until I was at least fifteen or so, though the belief had long since passed...
A childhood belief about disasters

others believed things like this
- i use to think that clouds were made from active volcanoes— brandyn
- I believed that Santa Clause lived on the moon. I mean how else could he see you when you was sleeping? — danger101
- I was told that if you sleep on your back you swallow your tongue...I have been sleeping on my side ever since— scotty la
- Long grass with black seeds were really ant hotels, and the seeds were sleeping ants.— angelsheep
- i used to think that when a fish floated to the top it was sleeping.— Kriket Evens
- I belived that santa came every night to se if i was sleeping— david