How A Volcano Works
1
Hot liquid rock (magma) from deep within the earth carves out a chamber as much as six miles below the surface. As the magma rises, gases trapped in it expand and bubble off.
2
The gases exert tremendous outward pressure that pushes the magma upward. As the magma comes into contact with groundwater, the water turns into steam and exerts more pressure.
3
The
magma and gases push through cracks in the mountain. (That's why
warning signs of an eruption include higher levels of carbon dioxide,
sulfur dioxide and other gases.) When the magma and gases reach the
surface, the pressure is suddenly released. The volcano erupts, shooting
out
rocks, ash, gases and lava.