Answer:
Volcanoes:
Volcanoes are cracks in the crust of the earth where magma, ash, steam, and gasses can vent onto the surface and into the atmosphere of the earth. Volcanic eruptions are the result of pressure and often occur in the subduction zone, where one tectonic plate is shoved under another. The subdued plate melts as it nears the mantle of the earth, but the mixture is more than just melted rock; it includes all kinds of substances and a lot of water. This builds pressure and the magma pushes up against the plate above it until it finds openings it can move through.
