David Smith, age 10, of Milwaukee, Wis., for his question:

What are Igneous rocks?

 The word igneous comes from an older word for fire, from the same ancestor word that gives us ignite. Igneous rocks are formed in fiery pools of molten magma deep below the surface, The seething magma contains all kinds of minerals and steamy gases, Sometimes it seethes up to the surface in volcanic eruptions. Sometimes it cools into solid rocks below the ground.

Those that come pouring forth are called extrusive igneous rocks. The various types of lava are extrusive rocks. Those that cool below ground are called intrusive igneous rocks. The granites are intrusive rocks. They often are buried deep underground but, when wind and weather wear away the rocky layers above them, they are exposed at the surface.