What is a Volcano? |
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A volcano is a mountain that opens downward to a pool of molten rock below the surface of the earth.
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When pressure builds up, eruptions occur.
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Gases and rock shoot up through the opening and spill over or fill the air with lava fragments.
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How Volcanoes form and erupt? |
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Volcanoes are formed when magma from within the Earth's upper mantle works its way to the surface.
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At the surface, it erupts to form lava flows and ash deposits.
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Over time as the volcano continues to erupt, it will get bigger and bigger.
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Classification of Volcanoes |
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Scientists have categorized volcanoes into three main categories:
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• Active
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• Dormant
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• Extinct
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An active volcano is one which has recently erupted and there is a possibility that it may erupt soon.
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A dormant volcano is one which has not erupted in a long time but there is a possibility it can erupt in the future.
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An extinct volcano is one which has erupted thousands of years ago and there’s no possibility of eruption.
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Types of volcanic eruptions |
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Since volcanoes erupt different from each other, depending on the kind of rising magma as well as other factors, we can distinguish various eruption types/styles.
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The most known types of eruptions are represented by the eruptions observed on:
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• Volcanoes of Hawaii (Hawaiian)
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• Stromboli (Strombolian) volcano
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• Vulcano (Vulcanian)
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• Mount/Montagne Pelée (Pelean)
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• Vesuvius (Plinian)
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However, most of the volcanic eruptions take place unseen on the ocean floor.
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Therefore, they are called submarine eruptions.
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Other types of eruptions include hydrovolcanic eruptions.
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Types of Volcanoes |
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• Ash-cinder volcano
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• Composite volcano
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• Shield volcano
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• Dome volcano
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Cinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent.
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Composite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris.
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Mt. Rainier and Mount St. Helens are examples of this type of volcano.
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Shield volcanoes are volcanoes shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows.
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Basalt lava flows from these volcanoes are called flood basalts.
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The volcanoes that formed the basalt of the Columbia Plateau were shield volcanoes.
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Lava domes are formed when erupting lava is too thick to flow and makes a steep-sided mound as the lava piles up near the volcanic vent.
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The eruption of Mount St. Helens in 1980 was caused in part by a lava dome shifting to allow explosive gas and steam to escape from inside the mountain.
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