Volcanoes
Volcanoes spew hot lava, volcanic ash and gases from a magma chamber inside. There are a wide variety of types of volcanos. They can continually erupt over many years, or build up pressure and erupt in an explosive manner that doesn’t last very long. Explosive volcanoes occur suddenly and can kill many more people than slower eruptions that give us warning to get far away from the source.
Figure 1: Cross section of a volcano
Figure 2: Spreading plate boundaries and volcano locations on Earth
Figure 1 shows a cross section of a volcano, showing the magma chamber at the bottom and the layers of ash that build up the mound that is the volcano. Volcanoes are located on the plate boundaries where the plates are spread- ing apart, allowing hot material from the mantle to penetrate the surface. They also occur intra-plate (in the middle of plates), in locations of hot spots. Figure 2 shows the location of spreading ridges and volcanoes all over the Earth.