Dana Lawson, age 12, of West Mifflin, Pennpylvania, for her question:

Is it true that oceans can manufacture rocks?

It is true that rocks are formed in and on the solid ocean floors. In fact, earth scientists now think that this is just where the bulk of the earth's crustal rocks are created. There are, of course, numerous recipes for making the numerous rocky minerals. All but a very few of them can be completed under the salty seas.

A generation or so ago, we were told that some of the sandstones, limestones and perhaps a few other common sedimentary rocks began to form under the oceans. It was assumed that most of the igneous rocks were formed by volcanos, erupting rivers of molten lava onto the land. It also was assumed that marbles and other metamorphic minerals were remodeled by the heat and pressure of energetic young mountains.

Well, the basic rocks have not changed. But earth scientists definitely have changed their minds about how, when, and especially where, most of them were manufac¬tured. This global switch of opinion occurred in the past three years, when the theory of continental drift graduated to the class of proven scientific facts. We now know that the continents drift around the globe     and also how they do it.

Naturally we want to bring our information up to date. However, this enormous concept involves the entire planet     plus a surprising number of events that go with it. For example, imagine how globe traveling continents have affected the distribution of plant and animal life. The gradually changing map also has affected ocean currents and perhaps climates.

This new global concept helps us to realize that ours is a watery world and that most of the earth's important events depend upon the vast oceans. This applies even to the rocks of the solid crust. We now know that enormous new batches are being formed along submarine ridges.

One of these well explored regions is the Mid Atlantic Ridge, a chain of massive mountains that snakes down the center of the North and South Atlantic Oceans. The crest of the great ridge is separated by an enormous trench, or rift. This is where molten lava constantly oozes up from the mantle below. There it cools to form new crustal sections. They cause the sea floor to spread and push the opposite sides of the Atlantic farther apart.

The spreading sea floors create new igneous material on a global scale. They have been doing this for at least a billion years, creating solid rocks to build sea¬beds, islands and continents. This may be the major rock building operation of our planet. However, the ocean also gathers oozy sediments to manufacture other rocky deposits.

Though most of the crustal minerals can be made by the ocean floor, other types require help from the land and the weathery air. Most surface sandstones and lime¬stones began as soggy sediments under the sea. But to become hard deposits, they had to be lifted high and dry above the water level. Desert rocks must be molded by desert winds.