Margaret Jubic, age 9, of Albany, New York, for her question:

What is the Continental Slope?

The continents, of course, are the earth's great big patches of dry land. Their shores reach the mighty oceans and the tides wash up and down on their beaches. Under the tidal waters is a sort of in between world that is neither dry land nor deep ocean. This is the continental shelf. Here the bed of the sea slopes gently downward from the land. And for this reason this part of the sea bed is called continental slope.

Along some shorelines, the underwater continental shelf is less than a mile wide. But most of the shelves are 50 to more than 200 miles wide. All of them slope down, down to deeper water. And all of them end with a sudden deep plunge to the ocean abyss. The immense oceans are held inside huge pits and valleys, in the earth's crust. These ocean basins are thousands of miles wide and from two to more than three miles deep. The sides of the basins are steep high cliffs. The sloping con¬tinental shelves end'where the floor of the sea plunges down these tremendous underwater cliffs.