When a region is clicked on, specifics come up. This cross-section shows the parts of a volcano. A conduit feeds magma to the surface. Near the surface, the gas expands and fragments the lava into ash. Some magma passes through dikes to feed vents.
Some magma intrudes parallel to layers to make sills.
Every year about 60 volcanoes erupt, but most of the activity is pretty weak. Volcano Volcanic eruptions are among the Earth's most powerful and destructive forces. Imagine hearing a volcano erupt thousands of miles away. Imagine looking through binoculars and seeing the top of a mountain collapse. Imagine discovering an ancient Roman city that had been buried in volcanic ash.