Kelvin Turner, age 11, of Peoria, I11., for his question:

WHERE DO 'ROCKS COME FROM?

There are hundreds of different rocks and every one has its own story to tell. All of them belong to the earth's crust and the restless earth is always remodeling them. Some of the great slabs were made with the mountains, long ages ago. Others were made from soggy sediments deposited in old lakes and seas. Meantime the weather and the running rivers did their best to break the big slabs into pebbles.

Geologists divide the rocks into three main groups. The igneous, or fire formed rocks, such as granites, are lavas erupted by volcanoes. Sedimentary rocks, such as slates and limestones, are hardened layers from old sea beds. Metamorphic, or altered, rocks are remodeled from other rocks. For example, shales are altered slates and marbles are altered limestones.