Different Types of Volcanoes Found Around the World

Volcanoes can vary by size and shape depending on where they are located around the world. There are several geologic factors that contribute to how a volcano forms, what types of eruptions it experiences, and how often an eruption occurs.

Volcanoes form on both land as well as deep under the sea. Volcanoes that form under the ocean occasionally expel enough material so that an island, or chain of islands rise up out of the ocean floor. Examples of island volcanoes are Hawaii and Iceland. A more recent example of an island rising from the sea occurred in 1963 when a volcano erupted about 400 feet below the surface of the ocean near Iceland. A small island rose up out of the ocean to form the island of Surtsey.

Volcanoes form over land form along the edge of continental boundaries, where edges of tectonic plates meet, like those located along the Pacific coast in Japan, Indonesia, and Washington State in the US. Inland volcanoes generally form over persistent hots spots, a perfect example being the Yellowstone Caldera. Inland rifts, like the East African Rift or Great Valley Rift are also volcano breeding grounds. Rifts are area where plates are pushing away from each other. Generally, rifts are found along the ocean floors, but the East African Rift occurs inland.

Volcano Classification
There are many geologic mechanisms that lead to the formation of volcanoes and scientist have been able to classify the different type of volcanoes found around the world based on their size, shape, appearance, and geologic factors that lead to their formation. A description of the different types of volcanoes found around the world follows.

Stratovolcano (Composite)
Many of the volcanoes located in the Cascade range fall into the category of being a stratovolcano. Mount St. Helen, Mount Hood, and Mount Ranier are classic examples. Others from around the world, include Pinatubo in the Philippines, and Tungurahua in Ecuador. Stratovolcanoes usually have steep sides that have been built up by lava and pyroclastic flows from activity spanning from years, decades or centuries of activity. There usually is a central vent or crater near the top of the volcano. Stratovolcanoes are also called composite volcanoes.

Caldera
A caldera is created when a large magma chamber develops beneath the surface of the earth, and an eruption occurs. The chamber empties of magma during the eruption and the chamber collapses leaving a large depression in the landscape. Caldera's can range in size from just a few miles to tens of miles across, or even larger. The largest caldera in the world is the Yellowstone Caldera, which was created by a series of magma chamber collapses. Another caldera can be found in Long Valley, California. Calderas can develop over inland hot spots, but are also prevalent across Iceland, Europe and Africa.

Shield
Shield volcanoes do not have as steep slopes like stratovolcanoes. Shield volcanoes are formed by lava flows along fissures in the earth. Shield volcanoes generally form along a line above a fissure or hot spot in the earth's crust. A chain of volcanoes along a fissure may also have shield and cinder cone structures. The chain of Hawaiian Islands make up one such group of volcanoes, with Mauna Loa and nearby Kilauea primary examples of shield volcanoes.

Compound
When more than one vent reaches to the surface, a volcano may take of multiple characteristics. These volcanoes are classified at compound volcanoes. The structures may form at different times. For example, an eruption at one vent may form a shield or a cone, while a nearby vent forms a stratovolcano. The Pacaya Volcano in Guatemala is made up of several peaks that each form its own stratovolcano, as well as smaller cones. It has been actively producing ash and lava at various intervals since 1965.

Rift
Tectonic plates literally float on the mantle of the earth to form the crust. There are regions were plates push up against one another, and then there are other regions were plates are moving away from each other. Areas were tectonic plates are moving away from each other are call rifts. A rift can form a long crack along the surface the earth. Magma is able to bubble up to the surface and volcano forms. The vents associated with rift volcanoes form a long line along the surface of the earth. Predominant rift areas occur along the ocean floor, like the Mid Atlantic Ridge. Along this ridge, lava has been pushed up out of the rift and flowed out to form a formidable north-south running ridge beneath the Atlantic Ocean. Sometimes enough lava and pyroclastic material is expelled to form islands, like Iceland. Many volcanoes in Iceland are rift volcanoes.

Table Mountain
These volcanoes occur as a result of volcanoes erupting under deep glaciers. The volcano is shaped upward as lava and gas expel upward, with little horizontal flow of lava. The result is a volcano that take on an almost cube shaped appearance. A classic example of a table mountain volcano is Herdubreid in Iceland. The volcano erupted along a fissure over 10,000 years ago when the fissure was under pack ice.

Cinder and Tuff Cones
Cinder cones form when only scoria is emitted during an eruption. Scoria are loose bits of magma that cool in flight as lava is ejected from the vent. Scoria is porous and light. Tuff cones are created from more explosive eruptions that eject ash and pumice. Paricutin Volcano in Mexico is a cinder cone. Paricutin rose up out of the ground rapidly out of a corn field in February of 1943. Within a day, a cinder cone 100 feet high was present as the eruption continued. The volcano continued to erupt until 1952, when it finally quieted down, leaving behind a new mountain that was over 1300 feet high.