Debra Woodman, age 10, of Saugus, Massachusetts, for her question:

What kind of land forms under the ocean?

         Every rocky formation in the earth's crust has its own dramatic story. But for convenience we class them in three major groups. The sedimentary rocks are hardened from mushy sediments that tend to sift down to the bottom of lakes and seas. The ig¬neous rocks are formed by the fiery fury of volcanoes. The metamorphic rocks are re¬made and remodeled from either sedimentary or igneous rocks. All these classes form on the land and also on the underwater bed of the ocean. Through ages past, many areas of dry land have been invaded and submerged by the ocean. And many times the sea bed has lifted up and its oozy floor has become dry land.

In some places, igneous lavas and hard metamorphic rocks formed under the sea have lifted up and become dry land. But most of the land reclaimed from the ocean is sedimentary rocks. These flat layers of silty sand and tiny sunken seashells sifted down to carpet the seabed. When they arose above water level, they became hard dry layers of shale and chalk, sandstone and limestone. Almost all these sedimentary lands originally were formed under water.