A tornado has a short life. From its birth to its death, the average tornado sweeps a path only 16 miles long. It travels along this path at a speed of from 25 to 40 miles an hour. This means that at any one place, the tornado completes its destruction in about 30 seconds. A prevailing wind carries the tornado along, usually driving it in a northeasterly direction in the United States.
Tornadoes have three destructive effects.
The winds blow down buildings and trees. Tornadoes also have a great explosive force caused by a difference in air pressures. For example, a tornado causes a sudden drop in the air pressure on the outside of a building. The air inside the building cannot escape fast enough to equalize the pressure on the walls and roof. This makes the building explode into a flattened pile of rubble.