Mike Stevens, age 12, of Visalia, Calif., for his question:

WHAT CAUSES A WHIRLPOOL?

'A whirlpool is a mass of water that spins around and around very quickly and with great force.

A number of different factors can cause a whirlpool. It may occur when the water current strikes against a bank which has a peculiar form. It may also occur when opposing currents meet or it may be caused by the action of y a wind.

Rocks or tides may get in the way of an ocean current. Whirlpools often form as a result.

One of the world's most famous whirlpools is in the gorge below the falls of the Niagara River. Another is the Maelstrom, which is off the coast of Norway and is formed by rocks and tides which oppose the current.