What is a Volcano and How are Volcanoes Formed?


A volcano is a fissure – opening or vent – in the earth’s crust through which molten rocks and gases erupt. The molten rocks can be in the form of mixture of hot gases, ash, lava, or other extremely hot substances within the earth’s crust.

A volcano looks like a huge heap of soil or a mountain, known as the cone, on the earth surface with a vent on the top. It takes this shape due to the continued piling of ash, dust, lava, and other substance for numerous years that pours out of the vent. Other volcanoes are deep depressions full of water.

According to National Geographic, “Volcanoes are awesome manifestations of the fiery power contained deep within the Earth. These formations are essentially vents on the Earth’s surface where molten rock, debris, and gases from the planet’s interior are emitted. When thick magma and large amounts of gas build up under the surface, eruptions can be explosive, expelling lava, rocks and ash into the air. Less gas and more viscous magma usually mean a less dramatic eruption, often causing streams of lava to ooze from the vent.

A volcano only remains active when it is releasing lava, gases or other substances. Most of the earth’s mountains, soils, plateaus, rocks, and plains present today are results of volcanic actions, including some of the spectacular sceneries such as Hawaii chain Islands and Costa Rica.

How are Volcanoes Formed?

The earth is made up of three layers: the outer crust, the mantle, and the core. The primary ingredient for the formation of volcanoes is the mantle which is made up of molten materials and gases commonly referred to as magma. When intense pressure develops within the mantle, particularly along fault lines, a volcanic eruption is very likely to occur. Fault lines are the weak areas, cracks, or openings in the earth’s crust. In the eruption process, the molten material turns into lava when it gushes out through the openings onto the earth’s surface.

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The process of volcanic formation begins as a result of tectonic plate movements on the earth’s surface. The tectonic plates are huge rock pieces floating on the surface of the mantle. Because the tectonic plates are floating, they are usually in constant slow motion by either moving towards each other or moving apart. As they collide or tear from each other, some may sink while others rise above thereby creating the lines of weakness, cracks, or openings in the earth’s crust.

When the tectonic plate sinks, it completely melts to form magma. Due to the underlying pressure and heat, the magma/mantle rises and tries to make its way through the crust thus bringing about a volcanic eruption when it manages to reach the earth surface. In most cases, the molten material finds way to the earth surface through the cracks or openings. However, at times when the pressure is not enough it doesn’t reach the surface. When the molten material reaches the earth surface, it is referred to as the lava.

Simply put, volcanoes form when the hot molten materials beneath the earth rise and escape into the crust. The hot material – magma, forms either from the melted sunken materials or from the interior part of the earth which is made up of hot liquid materials and gases. Because it is hot and filled with gases, it is lighter than the materials on top of it. Hence, whenever a fault line is present or a vent is created due to the sinking of tectonic plates; the pressure, buoyancy and heat rises and eventually reaches the surface to form a volcanic eruption.

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Powerful earthquakes normally accompany escaping magma and the volcano gets bigger as magma rises to the crust. Various factors influence the flow of the lava and the nature of volcanic occurrence. Factors such as the mineral content, amount of gas, molten capacity of the material, the underlying pressure, and the heat level largely determines the flow of the lava and the nature of volcanic formation.

For this reason, there are numerous types of lava, lava flows, and volcanoes. For instance, volcano categories include lava domes, cryptodomes, shield volcanoes, volcanic cones, composite volcanoes, and the list goes on.

The erupting lava can either be in the form of thick clouds or fragments shooting into the atmosphere. Some lava may also flow at a slow rate from the vent, flooding the area around it. Fine ash particles may as well be released into the higher atmosphere, visible from a long distance. Fresh lava is said to be approximately 2,200°F. The lava is red hot as it discharges from the vent but later cools off on the earth’s surface into magmatic or igneous rocks.

Photo by: WikiImages

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