According to the University of Wisconsin, a stratovolcano is characterized by a highly explosive eruption with ash plumes rising as high as 27 miles into the stratosphere. Stratovolcanos are one of the most deadly volcano types and can reach up to 8,000 feet in height.
The stratovolcano has an easily recognizable cone shape. Mount Fuji in Japan and Mount St. Helens in Washington are two examples of picturesque stratovolcanoes. The eruption of Mount St. Helens on May 18, 1980, which led to the destruction of over 230 square miles of forest and the death of 57 people, demonstrated the sheer power of stratovolcanoes.
The build up of pressure in the magma chamber causes the violent eruption seen in these volcano types. When magma reaches the conduit, the pressure is released, which causes the gases to explode in an extremely violent manner. Most active stratovolcanoes worldwide are less than 100,000 years old, although some, such as Mt. Rainier, may be more than 1 million years old.
A dormant stratovolcano has steep concave sides that sweep together at the top around a relatively small crater. Stratovolcanoes are also similar to shield volcanoes in the sense that both originate from a volcano that has erupted several times.