A composite volcano forms in subduction zones when a crustal plate is forced into the mantle and begins to melt. Andesite, dacite and rhyolite lavas are the primary types of lava that form these volcanoes. Eruptions on the volcanoes often alternate between tephra and lava flows.
Subduction zone volcanoes
Geologists often use the term stratovolcanoes to describe the mountains that form in subduction zones. The volcanoes form on the continental side of a subduction zone.
The melting oceanic crust forms pools of molten rock in a magma chamber. The magma, molten rock, in the magma chamber is lighter than the volcano rocks that surround it. The magma works its way to the summit where it erupts as tephra or in thick lava flows.
Lava eruptions on stratovolcanoes
Andesite, dacite and rhyolite are the three major types of lava that creates these large volcanic mountains on the continents. These three types of lava have a high percentage of quartz and are associated with large violent eruptions.
Stratovolcanoes will often alternate between explosive eruptions and thick lava flows. This combination of eruptions produces the classical look of a composite volcano.
Growth of the volcano
The summit of a stratovolcano has steep sides. Andesite, dacite and rhyolite create slowing thick lava flows that usually cool on the upper slopes of a volcano.
The base of these volcanoes is wide and has gentle slopes due to erosion. As the volcano grows in size large amounts of the pyroclastic material erodes away. The eroded pyroclastic material is carried down the slopes by erosion where it is deposited at the base of the volcano.
Yellowstone Caldera The Yellowstone Caldera is the location of three supervolcano eruptions.
Iceland Volcanoes Find out more about Grimsvotn volcano, Hekla volcano and Katla volcano which are the most dangerous volcanoes on Iceland.
Composite Volcano Composite volcanoes are volcanic mountains that form on the continental side of subduction zones.
Super Volcanoes Super volcanoes are places where massive volcanic eruptions occur. These eruptions can alter the weather and cause mini ice ages.
Dome Volcano A lava dome is small and often forms inside the caldera of a stratovolcano.
Volcano Facts Find out lots of fascinating facts and trivia about volcanoes on this webpage.
Home Page The Science Site contains information on our planet, volcanoes, science projects, earthquakes and much more.
Check out Myrna Martin's award winning textbooks, e-books, videos and rock sets. The Kids Fun Science Bookstore covers a wide range of earth science topics. Click here to browse.
Sign up to our monthly newsletter and receive our FREE eBook containing 3 fun activities that don’t appear in any of our other books!
The Kids Fun Science monthly newsletter will include the following: current events, weird and fantastic facts, a question of the month, science trivia and the latest new content from our website.
We respect your privacy and you can be assured that we will never share your email address or use it for any other purpose than to send you our newsletter.