Gary Bynum, age 9, of Santa Maria, Calif., for his question:

WHAT CAUSES A TIDAL WAVE?

    A tidal wave is not the same as the high tides that wash the beaches twice every day. It is a huge, huge hump of ocean water that deluges the land in a roaring flood. The high wall of water sweeps away everything in its path—then sinks back to the sea.      Sometimes a howling storm over the ocean may cause a tidal wave. But the worst ones are caused by seaquakes that happen in the deep ocean floor. This sort of dreadful tidal wave is called a tsunami.