Theresa Tenk, age 10, of Fairview Park, Ohio, for her question:

How wide is the Continental Shelf off our Atlantic coast?

Our Atlantic coast reaches several thousand miles from north to south. The pattern of the shoreline varies and so does the deep ocean basin off the coast. The Continental Shelf is under water, but it is a sort of sloping doorstep from the land dipping toward the steep cliffs that plunge down to the deep ocean basin. Along our Atlantic shores, the Continental Shelf varies in both depth and width. Off Canada and New England, the gentle slope is 100 to 150 miles wide. This is much wider than our Pacific Shelf and most other world shelves.

Off our Southern States, the Continental Shelf becomes narrower. Off Cape Hatteras, the underwater tide lands dip sharply for just a few miles, then the sea floor plunges down to the ocean basin. Off the eastern shore of Florida, the Shelf becomes still narrower and at the tip of the peninsula, it is a mere threshold from the sandy beaches to the deep abyss of the Atlantic Ocean.