Types of Volcanoes
For billions of years volcanoes have devastated the Earth’s surface and altered its atmosphere with little warning. Volcanoes have terrified, awed, and altered humans’ lives, and are capable of destroying entire cities with their molten hot lava and poisonous gasses. There is evidence of their awesome power throughout history, and many humans have dedicated their lives to studying their formation, their explosive characteristics, and their impact on the environment.
A volcano can be defined as a rupture on the Earth’s crust that allows for ash and lava to break through and escape from the inside of the Earth onto the surface. Magma is the hot molten rock that lies below the surface of the Earth, and is considered lava
only after the molten rock breaks onto the Earth’s surface. There are
many different types of volcanoes that can be found on Earth, and each
volcano can be classified according to its location, build, and lava
composition.
Stratovolcanoes
Stratovolcanoes, or composite volcanoes, are classic, cone-shaped volcanoes. They have steep sides and are often thousands of feet tall. Stratovolcanoes are found where the Earth’s crust converges and a subduction zone is formed. Stratovolcanoes produce lava that is high in silica and high in gas content. The higher the silica, the gooier the lava flow. In other words, lava from a stratovolcano flows more like honey than like water. Higher gas content indicates that the lava will form more holes as it cools.
Mount Vesuvius, which erupted and destroyed the town of Pompeii, is a classic example of a stratovolcano. This volcano is well known for an eruption in A.D. 79 that buried the towns of Pompeii and Herculaneum under a deadly pile of ash and other toxic material.
Cinder Cone Volcanoes
Cinder cone volcanoes are known as parasitic volcanoes because they form off of the sides of stratovolcanoes. These volcanoes are usually small in size (less than 1000 feet high), and are built from cinder-sized fragments of ejected lava. Cinder cone volcanoes are abundant worldwide, and often occur in groups. Due to the loose structure of the cinder cone volcano, pressure cannot build up, so lava oozes out of the base of the volcano instead of spewing out of the top. The lava is low in gas content, and is therefore high in density, which is another reason why it rarely breaches the top of the volcano.
Wizard Island is an extinct cinder cone volcano that formed off of stratovolcano Mount Mazama in Crater Lake, Oregon after
Mount Mazama erupted around 4680 B.C.E. Wizard Island and Crater Lake
are revered by the Native American Klamath Tribe because the tribe
supposedly witnessed the explosion.
Shield Volcanoes
Shield volcanoes are the largest type of volcano found on Earth. They are shaped like a dome, and have long, broad slopes (like a shield laying face up). Shield volcanoes are located along hot spots and divergent boundaries. The lava from a shield volcano is typically low in silica and in gas content. In other words, the lava from a shield volcano flows more like water than like honey.
A common example of a shield volcano can be found in Hawaii, USA. Mauna Loa is a shield volcano that composes the “big” island of Hawaii. It is also the largest single mountain in the world. Its last eruption was in the spring of 1984. Due to its unstable position and close proximity to large populations, Mauna Loa undergoes an intense amount of monitoring and research within the Decades Volcanoes program.
Supervolcanoes
Supervolcanoes are characterized by large magma chambers that build up over periods of thousands of years before finally erupting. They do not have steep slopes like stratovolcanoes, and they are more difficult to locate with an untrained eye. Supervolcanoes are known for spewing large amounts of lava and gas into the atmosphere and are responsible for drastic changes in weather. They have also been known to cause mass extinctions.
Although the latest supervolcano eruption occurred over 27,000 years ago in Taupo, New Zealand, geologists estimate that there are about 40 dormant supervolcanoes on Earth.
For billions of years volcanoes have devastated the Earth’s surface and altered its atmosphere with little warning. Volcanoes have terrified, awed, and altered humans’ lives, and are capable of destroying entire cities with their molten hot lava and poisonous gasses. There is evidence of their awesome power throughout history, and many humans have dedicated their lives to studying their formation, their explosive characteristics, and their impact on the environment.
A volcano can be defined as a rupture on the Earth’s crust that allows for ash and lava to break through and escape from the inside of the Earth onto the surface. Magma is the hot molten rock that lies below the surface of the Earth, and is considered lava
only after the molten rock breaks onto the Earth’s surface. There are
many different types of volcanoes that can be found on Earth, and each
volcano can be classified according to its location, build, and lava
composition.
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Stratovolcanoes, or composite volcanoes, are classic, cone-shaped volcanoes. They have steep sides and are often thousands of feet tall. Stratovolcanoes are found where the Earth’s crust converges and a subduction zone is formed. Stratovolcanoes produce lava that is high in silica and high in gas content. The higher the silica, the gooier the lava flow. In other words, lava from a stratovolcano flows more like honey than like water. Higher gas content indicates that the lava will form more holes as it cools.
Mount Vesuvius, which erupted and destroyed the town of Pompeii, is a classic example of a stratovolcano. This volcano is well known for an eruption in A.D. 79 that buried the towns of Pompeii and Herculaneum under a deadly pile of ash and other toxic material.
Cinder Cone Volcanoes
Cinder cone volcanoes are known as parasitic volcanoes because they form off of the sides of stratovolcanoes. These volcanoes are usually small in size (less than 1000 feet high), and are built from cinder-sized fragments of ejected lava. Cinder cone volcanoes are abundant worldwide, and often occur in groups. Due to the loose structure of the cinder cone volcano, pressure cannot build up, so lava oozes out of the base of the volcano instead of spewing out of the top. The lava is low in gas content, and is therefore high in density, which is another reason why it rarely breaches the top of the volcano.
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Shield Volcanoes
Shield volcanoes are the largest type of volcano found on Earth. They are shaped like a dome, and have long, broad slopes (like a shield laying face up). Shield volcanoes are located along hot spots and divergent boundaries. The lava from a shield volcano is typically low in silica and in gas content. In other words, the lava from a shield volcano flows more like water than like honey.
A common example of a shield volcano can be found in Hawaii, USA. Mauna Loa is a shield volcano that composes the “big” island of Hawaii. It is also the largest single mountain in the world. Its last eruption was in the spring of 1984. Due to its unstable position and close proximity to large populations, Mauna Loa undergoes an intense amount of monitoring and research within the Decades Volcanoes program.
Supervolcanoes
Supervolcanoes are characterized by large magma chambers that build up over periods of thousands of years before finally erupting. They do not have steep slopes like stratovolcanoes, and they are more difficult to locate with an untrained eye. Supervolcanoes are known for spewing large amounts of lava and gas into the atmosphere and are responsible for drastic changes in weather. They have also been known to cause mass extinctions.
Although the latest supervolcano eruption occurred over 27,000 years ago in Taupo, New Zealand, geologists estimate that there are about 40 dormant supervolcanoes on Earth.