World Map of Volcano Types

What is a Volcano

A volcano is an opening on Earth's crust. These openings allow material warmer than its surroundings to escape from its interior.

The material that escapes or erupts can be lava, small rocks, volcanic ash, or steam.

Deep underneath a volcano is molten rock called Magma. Magma is lighter than the surrounding rock. With the pressure of the gases in it, magma rises and forces its way through cracks on Earth's crust.

As it rises it breaks through the Earth's crust as an eruption. Once it is out, the Magma is called lava. The way this eruptions occur depend on the gas content and chemical composition of the lava.

Volcanoes with low gas content have runny and slow erupting lava. Examples of this, are the volcanoes in the Hawaiian Islands.

Volcanoes with lots of trapped gas, high viscosity, and silica, have more explosive eruptions like that of Mount St. Helens in the State of Washington.

Explosive eruptions are accompanied by strong earthquakes.

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Where are Volcanoes Located

Most volcanoes are found at the edges of Tectonic Plates. These edges can be under land or under oceans.

Plate Tectonics is a theory that explains how the Earth's outer most layer is divided into plates. These plates move over the molten upper portion of the Earth's mantle. Convection currents under the plates move the plates in different directions.

This motion means that plates come together and spread apart. There are margins where the tectonic plates meet and there is no friction. These are called passive margins. Like the East Coast of the United States.

Active margins are sites where plates meet and collide. In this collision one plate can go underneath the other. This will result in a trench, and a lifting of a continental plate.

The plate that sinks goes into great heat and pressure. This material mixes and melts turning into liquid magma. This molten magma is more bouyant than the material above. This buoyant magma eventually migrates to the surface in the form of volcanoes.

A clear example of this collision of plates is the Western Coast of South America. You can see in the map above, this margin is covered with volcanoes.

The Plate under the Pacific Ocean is going underneath the South American Continent, creating the Andes mountains and a chain of volcanoes with it. The same situation occurs on the other side of the Pacific, where Asia meets the Ocean Open Geology.

In the map above the lighter shade of blue on the ocean floor represents lower depth. This are usually divergent margins or where the tectonic plates are separating.

This areas are also active. They are called mid-ocean ridges. You can see them clearly in the middle of the Atlantic Ocean. These areas also have volcanic activity due to the movement of magma.

If you would like to read a bit more about tectonic plates and about the geology of Earth, I suggest you get this book from Amazon called Origins: The Evolution of Continents, Oceans and Life. The book is full of illustrations and photos, explaining the origin of different geologic features around the world.

Volcano Types

Volcanoes are characterized by their composition, structure, and eruption. They also vary, depending on the rocks, and minerals that make them up.

Below you can read the four major types of Volcanoes, Source: http://ete.cet.edu/gcc/?/volcanoes_types/.

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Cinder Cones

A cinder (also called scoria) is pyroclastic material. They are extrusive igneous rocks, that come from fragments of solidified lava. Cinders look like dark pumice.

When cinder volcanoes erupt, powerful blasts throw molten rocks, ash, and gas into the air. These pieces dry and fall as pieces of cinder that accumulate near the vent forming a circular cone.

Most cinder cones have a bowl shaped crater.

Cinder cones are mainly made of accumulated, loose grainy cinders and almost no lava. They are usually small volcanoes of about one mile in diameter and 1,000 feet high.

Cinder Cones have steep sides and a small crater on top. It is not uncommon to find Cinder cones as part, next, or at the flanks of other volcanoes.

They are usually formed later in an eruption when activity has localized to one or more discrete vents.

Mount Etna in Sicily is covered with Cinder Cones. Paricutin Volcano in Mexico is another well studied example of a Cinder Cone Volcano.

For a comprehensive guide on volcanoes and detailed information on what is known about them, I suggest you get from Amazon The Encyclopedia of Volcanoes. Packed with information about eruptions, magma, source rocks, geothermal energy, and eruption effects on ecology.

Coral Reefs are likely to grow over the remains of underwater volcanoes. To learn more, click here!

Shield Volcanoes

Shield volcanoes are mainly made of thin lava built in the central vent. These volcanoes have very little pyroclastic material. Therefore, Shield volcanoes form from nonexplosive eruptions of low viscosity magma.

After lava pours out in all directions from the central vent, or group of vents, it builds a broad, gentle sloping flat cone.

These volcanoes tend to have large calderas at their summits.

Because they build up slowly through accretion, this type of volcano can be hundreds of miles across and can be on average 2,000 feet high.

Shield volcanoes have slopes from 10 degrees to 5 degrees at the top.

Some of these eruptions will pour basaltic lava from long fissures instead of central vents. They can flood surrounding areas with successive flows, eventually forming plateaus.

A well-known example of Shield Volcano is Maunaa Loa on the "Big" island in Hawaii.

If you want to read more in depth information about active and new volcanoes, here is a link from Amazon to Volcanoes of the World. It contains a directory of volcanoes with a chronology of eruptions.

Stratovolcanoes or Composite Volcanoes

Stratovolcanoes are made of layers of lava flows interlayered with sand or gravel from volcanic rock or ash. The volcano is build up by the accumulation of material erupted.

These volcanoes are usually 10-20 miles in diameter and can reach around 10,000 feet. The slopes of this type of volcano start at 10 degrees and reach 30 degrees at the top.

Their interlayering is usually 50% lava and 50% pyroclastic material.

Pyroclastic material are mixtures of hot dry rock, cinders, and gases that are usually erupted at high speeds and strong explosions.

Lava may escape through the cracks in the crater wall or through fissures on the sides of the cone.

Lava that solidifies in the fissures, form dikes that will act as ribs giving more strength to the cone USGS.

When these volcanoes become dormant, erosion slowly degrades the cone. Then the hardened magma of the conduit and dikes are exposed. These are eventually eroded away as well.

Some of the most conspicuous and beautiful mountains, are Composite volcanoes.

Famous stratovolcanoes include Krakatoa in Indonesia which had a catastrophic eruption in the 1800's and Mount Vesuvius in Italy.

The tallest Stratovolcano in the US is Mount Rainier, with a summit elevation of 14,410 feet. Another famous Stratovolcano is Mount Fuji in Japan.

These volcanoes are depicted with red in the Map above.

For more facts and information about volcanoes, Amazon has Volcano: Live, Dormant and Extinct Volcanoes Around the World (Wonders of Our Planet). This book is a fascinating visual journey around the globe, selecting the most striking live and extinct volcanoes from Alaska to Antarctica, from Tanzania to Tasmania, from Kamchatka in Russia's far east to Indonesia and the Philippines.

Interested in what is under the surface? Check this detailed map of Florida's Geology.

Lava Domes

Lava Domes are made of lava flows that are too thick to move or flow away from the vent.

Eventually the lava accumulates and squeezes near the vent as a giant pile.

This accumulation may result in spines or tops that look like muffins, or like tongues.

Some domes form ragged lumps or spines over the volcanic vent, whereas others form short, steep-sided lava flows known as "coulees.

This type of volcano is quite dangerous, because they grow from inner expansion.

As the lower magma accumulates the cold hard top can shatter and spill hot rocks down its flanks.

An example of a Lava Dome volcano is Katmai Volcano, in Alaska USGS.

Other types of volcanoes

The previous four types of volcanoes are the most common. There are other types that are on the map. Here is a brief description of some of them.

Strato Volcanoes and Shield Volcanoes can lose their tops following a large explosion. The result is the collapse of the top leaving a depression which may later form a Caldera.

The diameter of a Caldera can be 15 miles to 60 miles long.

A Maar is a broad, flat volcanic crater caused by an explosion which occurs when groundwater comes into contact with hot lava or magma.

A maar usually fills with water to form a relatively shallow crater lake.

A "complex volcano" does not have just one main vent or cone but several eruption points that have changed over time.

Fumaroles are openings on the Earth's crust that emit volcanic gases like sulfur dioxide, carbon dioxide, or steam. They may happen as fissures near active volcanoes or areas where magma raised close to the surface but never erupted. Source: USGS

Many volcanoes are vents or fissures under the ocean. This are the Submarine volcanoes. The most productive volcanic systems on Earth are under the water at an average depth of 8,500 feet (2,600 m).

These are the Submarine Volcanoes, and they are likely found under the mid-ocean ridges.

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Volcano Map and Sources

This map only shows volcanoes that have been active in the last 10,000 years or during the Holocene. The data is a collection of information by Smithsonian Institution volcanologists summarizing 1,509 volcanoes.

The Shapefiles for the volcanoes and their information was downloaded from Stanford.

The Shapefiles with the depths and countries was downloaded from Natural Earth.

This map will be updated with new data! To receive updates on this and more nature maps join my email list!!!!!!!

Made by Luz K. Molina with D3.js.