Stratovolcano / Composite volcano
Composite and Stratovolcanoes are one and the same. They are the volcano diagram that we all drew at school with layers of ash and lava. They are normaly located above subduction zones and erupt explosively. Viscous lava, ash,tephra and pyroclastic flows build up a steep sided cone with a crater(s) at the summit. The volaco can erupt a variety of lava types from black basalt, through andsite and sticky dacite to the eruptive equivalent of granite- rhyolite. This variety of lavas is due to cooling and crystallisation of the magma within the volcano changing the composition of the melt when it is erupted. The volcano may have smaller parasitic cones. Domes of lava may form in the summit craters.
Mt.St.Helens and Mt.Rainier in the Cascades are both Stratovolcanoes.