A composite volcano is also known as a stratovolcano. These volcanoes form tall, conical shaped mountains. Most of the Earth's active volcanoes have formed a ring around the Pacific Ocean. There are 452 stratovolcanoes in the Pacific Ring of Fire. The volcanoes are located in a volcanic arc on the continental side of subduction zones.
1980 Mount Saint Helens eruption, USGS
Composition of stratovolcanoes
Stratovolcanoes are typically composed of layers of pyroclastic material. The layers that form the mountain are lava, volcanic ash, tephra, and pumice. Andesite, dacite and rhyolite lavas erupted by these volcanoes have a high percentage of quartz and feldspar minerals.
Minerals in lavas
The minerals in these lavas can be highly explosive because the gases in the magma cannot easily escape. The lava is less fluid and forms thick lava flows on the sides of the volcano. Sometimes the lavas form small dome volcanoes over the vent in the crater of a stratovolcano or on its steep sides.
Eruptions of statovolcanoes
Stratovolcanoes erupt less frequently than shield volcanoes which have formed over hot spots. The lava is less fluid and often erupts with explosive eruptions that produce deadly pyroclastic flows.
The eruptions of Krakatoa in 1883, Mount Saint Helens in 1980 and Mount Pinatubo in 1992 were examples of large volcanic eruptions by stratovolcanoes.
Cascadia Subduction Zone Learn more about the Cascadia Subduction Zone in the Pacific Northwest where a great earthquake could occur at any time.
2010 Chilean Earthquake Another megathrust earthquake struck Chile in 2010. Find out why these earthquakes occur so frequently there.
Island Arcs Island arcs are a string of volcanic islands in the ocean. Find out more about these islands in the Pacific Ocean.
Strike Slip Fault Learn more about strike slip faults that are boundaries between crustal plates including the San Andreas Fault.
Subduction Zones Find out why the Pacific Ring of Fire has so many subduction zones.
Composite Volcano Learn more about these towering mountains that form on the continents near subduction zones.
Pacific Ring of Fire Learn more about the Ring of Fire which is home to towering volcanoes and great earthquakes.
Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more.