A stratovolcano is a type of volcano characterized by its steep, conical shape and layered structure. These volcanoes are formed from alternating eruptions of lava, ash, and other volcanic materials. The lava is typically thick and viscous, which causes it to flow slowly and build up the volcano's height over time. Stratovolcanoes are often associated with explosive eruptions due to the pressure that builds up from gas trapped in the thick lava. Famous examples of stratovolcanoes include Mount St. Helens in the United States and Mount Fuji in Japan. They are commonly found at convergent plate boundaries, where tectonic plates collide.