Tom Sarazin, Age 9, Of  Mauston, Wisc., for his question:

Why does old faithful gush at the same time?

Old faithful is not as good at clocking the time as a watch. When the old geyser spits up his tall fountain of streamy water, you can expect another show in about 65 minutes. But you cannot be sure he will perform exactly on time. He may spout after 50 minutes or wait for 75 minutes. Actually, this steamy geyser in yellowstone national park is run by an underground teakettle, and it must wait for the kettle to fill with water and come to a boil.

The rocks below ground are heated by buried lava. Water from rains and melting snows seeps down among the warm rocks and collects in buried holes and cracks, crevices and deep pockets. The underground kett1e fills up and the water is heated by the rocks. The water boils and gushes up in a steamy spout. This empties the kett1e, and old faithful must wait for another pot of steaming water before he can erupt again.