Wai Young Chong, age 10, of Toronto, Ontario, Canada, for his question:

How does a volcano form?

The real action begins miles underground. Volcanos are likely to form where the earth's crust is building new mountains or creating other disturbances on a grand scale. When this happens, massive blocks of the rocky crust are heaved and shoved, bent and cracked and stacked like giant sandwiches. The weighty slabs press down and the underground heat and pressure can provide the energy to form a volcano.

It can melt solid rocks and create great pools of molten magma, perhaps miles below the surface. The heavy rocks above try to keep it capped. But as the moving mountains grow, they make cracks and weak spots in the upper crust. When this happens, the pressure is taken off the buried magma. The seething mixture erupts up the crack or vent, like a monstrous bottle of pop when the cap comes off. Anew volcano is born and its mixture of molten minerals and steamy gases pour out rivers of red hot lava.