Jeffery Peters, age 10, of Walnut Creek, Calif., for his question:

WHAT IS LAVA MADE OF?

Lava is the molten rock that pours out of volcanoes. It comes from deep within the earth where the heat is great. It is a solution of silicate materials. The lava hardens into a rock that contains  large amounts of natural gas.

Some types of lava contain large amounts of dissolved gases. As the gases expand, they are trapped in the lava, and form many bubbles. Pumice is a type of lava that contains many bubbles.

Lands that were once covered with lava often become quite fertile after weathering has broken the lava into fine soil.

The islands of Hawaii are a chain of volcanoes built mostly of lava. The mountain belt of southern Mexico, with its hundreds of volcanoes, also has a great lava pile.