Volcano A volcano is a land form, which is essentially a vent that emits magma (molten rock), volcanic ash, gases, and pyroclastic debris through the Earth’s crust. It can also be called an opening. The word volcano comes from Vulcan, the Roman god of fire. Volcanoes exist between tectonic plates. Tectonic plates are large slabs of rocks that make up the Earth’s surface.

Examples of Volcano

Origin of volcanoes A volcano is a result of a denser crust subducting below another crust (it creates friction) that makes the magma below the Earth’s crust find an exit. Simply put, it is a result of the plate tectonics theory when two plates collide to each other. It is an example of a convergent plate boundary. Another one is the divergent plate boundary where to plates move away from each other. The plate tectonic theory explains the movement of plates which results to different land forms (including volcanoes) and earthquakes.

Origin of volcanoes Other volcanoes come from “hotspots”. Hotspots are due to hot mantle pumes rising through the crust. Basically, magma rising up from the mantle. This is one theory that explains the formation of the Hawaiian islands and the chains of volcanoes.

Types of Volcanoes Cinder Cones StratoVolcanoes Caldera Shield Volcanoes

Cinder Cones Cinder cones, also known as volcanic cones, are volcanoes that are the result of eruptions of pyroclastics and cinders which build up around the vent. These eruptions form a cone-shaped hill. Most cinder cones erupt only once. Paricutin in Mexico and Cerro Negro in Nicaragua are examples of cinder cones.

Stratovolcanoes Straotovolcanoes are also known as composite volcanoes. They are conical volcanoes. These volcanoes are composed of layers of hardened lava, tephra, pumice, and volcanic ash. According to history, eruptions from stratovolcanoes make the greatest destruction to human civilization. Some examples of stratovolcanoes are: Mt. Fuji in Japan, Mt. Mayon and Mt. Pinatubo in the Philippines, and Mt Vesuvius and Mt. Stromboli in Italy.

Caldera A caldera is a cauldron-like volcanic feature. This word comes from the Spanish word caldera and the Latin word caldria which means “cooking-pot”. It is the collapsing of the land due to the eruption. Supervolcanoes usually have large calderas.

Shield Volcanoes A shield volcano is usually made entirely of fluid lava flows. They are formed by the eruption of low viscosity lava. Lava flow from shield volcanoes travel farther than lava from more explosive volcanoes. The Hawaiian volcanic chain is an example of a shield volcano.

Volcanic outputs Lava Cinders Bombs Rocks Gases

Lava Lava is the molten rock (magma) that is expelled from a volcano. The molten rock is formed in the interior of the planet or satellite. Lava can also mean the rock it became after cooling and crystallization. Lava can be classified into four groups according to chemical composition : felsic, intermediate, mafic, and ultramafic.

Felsic Lava Felsic lava is also known as silicic lava. This lava has a high silica content (more than 63%). This kind of lava forms lava spines, stratovolcanoes, and thick short lavas or “coulees”. Felsic lava has high viscosity which makes it slow moving. Rocks that are formed from felsic lavas are dacites and rhyolites.

Intermediate Lava It is also known as Andesitic lava. This lava is formed at convergent plate boundaries. The intermediate lava contains 52-63% silica. The eruption that contains this lava generally occur above subduction zones. It is rich in magnesium and iron but lower in aluminium and silica compared to the felsic lava. Intermediate lavas are less viscous.

Mafic lava Mafic lava is also known as basaltic lava. It has a high ferromagnesian content. This lava is high in iron and magnesium but low in aluminium and silica. The viscosity of the basaltic lava is low. Most basaltic lava are of Aa and Pahoehoe types. You can see large, well-formed phenocrysts within mafic lavas. It contains <52% but >45% silica.

Aa It’s from Hawaiian which means “stony rough lava”. It is characterized by a rough lava composed of broken lava blocks. Aa has a higher viscosity than pahoehoe. It makes a strong radar reflector. It can easily be seen by an orbiting satellite. Aa lavas erupt at temperatures: 1000 to 1100 °C Flows of this lava can be thick and can reach up to 100 meters.

Pahoehoe It means “smooth, unbroken lava”. When it cools, it forms a smooth surface. It has a low viscosity. Pahoehoe flows may change into Aa flows due to heat loss and increase in viscosity. Pahoehoe lavas typically have a temperature of 1100 to 1200 °C. It has a rounded texture. The pahoehoe is a poor radar reflector.

Cinders Cinders are pyroclastic materials that are partly burned. They are also fragments of ash. They are extrusive igneous rocks. They are also similar to pumice. They are not cemented. Their color is usually red or black. Cinders have been used on track surfaces and roads.

Volcanic Bomb It is a mass of molten rock or tephra. They are formed during an eruption of a volcano. Once they cool, they became extrusive igmeous rocks. They don’t have grains. There are many kinds of bombs like the ribbon or cylindrical bombs, the spherical bombs, cored bombs, etc.

Famous Volcanoes Mt. Pinatubo Mt. Mayon Mauna Loa Mt. St. Helens Vesuvius Stromboli

Mt. Pinatubo Mt, Pinatubo is an active stratovolcano in the Philippines (In Zambales, Tarlac and Pampanga). It is famous around the world because of its 1991 eruption which lowered the Earth’s temperature by a few degrees.

Mt. Mayon Mayon is an active volcano in Albay (Region 5). It is famous for its “perfect cone” structure. It is also an example of a stratovolcano.

Mauna Loa Mauna loa is an active volcano in hawaii. It is one of the volcanoes that form the island. It is the world’s largest shield volcano.

Mt. St. Helens Mt. St. Helens is an active stratovolcano located Washington in the US. Its most destructive eruption was on May 18, 1980.

Vesuvius Mount Vesuvius is a stratovolcano located in Italy. This volcano is seen from the ruins of Pompeii. It is famous for its eruption during the 79 A.D. Which buried the city of Pompeii.

Stromboli Mt. Stromboli is a stratovolcano located in the islands of Stromboli. It has been continuously erupting for the past 2000 years. Its eruptions are somewhat explosive.

SOURCES Google Images Wikipidea Geology for Kids Youtube videos of volcanoes