What Is a Stratovolcano?

Stratovolcanoes are the most common type of volcanoes, and they are characterized by steep upper summits, including volcanoes like Mt. Fuji and Mt. Mayon. Also known as composite cones, these volcanoes are typically built over many thousands of years.

In addition to having a picturesque appearance with pointed summits (except in the case of those volcanoes that have recently erupted, like Mt. St. Helens), stratovolcanoes usually consist of multiple vents and erupt with a variety of magma types. Stratovolcanoes are built by lava flows, tephra and pyroclastic flows, and they usually have very small craters except in the cases of stratovolcanoes like Mt. St. Helens that have recently "blown their tops" so to speak. St. Helens lost a significant part of its peak in its 1980 eruption due to a lateral blast.

According to Oregon State University, part of the risk associated with a stratovolcano eruption, in addition to ash clouds, debris fall and lava flow, is the occurrence of lahars, which is an Indonesian word meaning "mudflow." Errupting stratovolcanoes that have a large amount of snow at their peak can result in a massive, sudden amount of snowmelt that runs down the mountain and causes huge amounts of damage to life, property and the natural world.