Stratovolcanoes, also known as composite volcanoes, are tall, steep-sided volcanoes characterized by their conical shape. They are formed by layers of hardened lava, tephra, pumice, and volcanic ash. Stratovolcanoes are typically found at subduction zones, where one tectonic plate is forced beneath another. The magma that forms stratovolcanoes is viscous and tends to trap gases, leading to explosive eruptions. Over time, layers of erupted material build up, creating the steep profile of a stratovolcano.