Becky Plagman, age 14 of Linn Grove, Ia., for her question:

Why are hot springs hot?

A bubbling hot spring tells us a tale of volcanic activity. The ground from which it comes was once a bed of seething lava. The surface of the molten rock cooled fast in the air and formed a solid crust. This sealed the heat in the lower levels and stopped it from escaping. In a region of hot springs and geysers, the ground below the surface still has some of the heat from ancient volcanic activity.

Rains and streams seep down into these lower layers of heated rock. The ground water touches the heated rock and becomes warm or steaming hot. In time, it finds a path to the surface and gushes forth as a plumy geyser or a bubbling hot spring.