Susan Ferency, age 13, of Fairfield, Conn., for her question:

WHAT ARE THE CONTINENTAL SHELVES?

Around many of the continents, the land gradually drops under water to a depth of about 600 feet and it continues at this depth for many miles. This submerged land is called the continental shelf.

In some places the continental shelf extends for many hundred miles. In other spots it hardly exists because the coastline drops nearly straight down into very deep water.

The shelves are covered with a material called the continental deposit which has been carried down from the land by rivers.

The great fisheries of the world are almost all located on continental shelves, making the areas the most important part of the oceans. Many oil fields are also located here.