A volcano is a rupture in the Earth’s crust that lets gases, debris and molten rocks escape from a magma chamber inside the Earth’s surface. During volcanic activities, debris and lava can flow at a velocity of up to 100mph, demolishing everything in their way. Volcanic ashes can spread across hundreds of kilometres and can inflict fatal health problems.
The term volcano was derived from the word “Vulcano” (a volcanic island in the group of Aeolian Islands). The word “Vulcano” was derived from “Vulcan”, the Roman god of fire. Volcanology is the study of volcanoes.
The rigid lithosphere is divided into 16 larger and numerous smaller plates, according to plate tectonics theory. All of these plates are in slow motion. Volcanoes generally exist where tectonic plates are converging or diverging. The majority of them are found underwater. In the Mid-Atlantic Ridge, volcanoes were formed from diverging tectonic plates. On the other hand, volcanoes in the Pacific Ring of Fire were formed by converging tectonic plates. They can also be created from where there is thinning and stretching of the crust’s plates. Two such examples are the Rio Grande Rift and the East African Rift. Volcanoes usually do not exist where two tectonic plates slip past one another. About 75 percent of the Earth’s active volcanoes are located around the ring of fire (25,000-mile long). It is a horseshoe-shaped area that extends from the Southern point of South America across North America’s west coast, along the Bering Sea to Japan and ending at New Zealand.
The video explains the basic concepts of volcano eruptions.
Eruption types are divided into phreatic, pragmatic and phreatomagmatic eruptions. High viscosity magma with a high amount of dissolved gas generates intense explosive eruptions. Low viscosity magma with a low quantity of dissolved gases causes comparatively gentle effusive eruptions. Phreatomagmatic eruptions are produced by the activity of rising magma with groundwater. They are propelled by the resulting accelerated buildup of pressure in the extremely heated groundwater. Phreatic eruptions are created by the superheating of groundwater that is exposed to hot magma or rock. They are different from phreatomagmatic eruptions because the exploded material is all country-rock, no magma is ejected.
Volcanic explosions pose many hazards apart from lava flows. Massive eruptions can alter atmospheric temperature as sulfuric acid droplets and ash block the Sun, which cool the troposphere. Throughout history, huge volcanic explosions have been accompanied by volcanic winters, which have paved the way for catastrophic famines. Volcanic eruptions are followed by pyroclastic flows. It is a mix of ash, high-speed toxic gases and avalanches of hot rocks. Such a phenomenon was the primary reason for wiping out the entire population of Herculaneum and Pompeii when Mount Vesuvius exploded in A.D. 79. Likewise, volcanic mudflows known as lahars can be devastating. These fast-moving waves of debris and mud can flow down the flanks of a volcano, engulfing entire towns. Volcanic ash is another serious threat to nature. It consists of sharp bits of rocks and volcanic glass, smaller than two millimetres across. The ash generates as the gases in the rising magma enlarge, disintegrating the cooling rocks as they explode from the volcano’s mouth. It causes breathing problems, and it is heavy and multiplies quickly. Removal of ash is a serious challenge post-eruption.
Important Volcanoes Questions with Answers
1) What is a volcano?
A volcano is a rupture in the Earth’s crust that lets gases, debris and molten rocks escape from a magma chamber inside the Earth’s surface. During volcanic activities, debris and lava can flow at a velocity of up to 100mph, demolishing everything in their way. Volcanic ashes can spread across hundreds of kilometres and can inflict fatal health problems.
2) Where did the term volcano come from?
The term volcano is derived from the word “Vulcano” (a volcanic island in the group of Aeolian Islands). The “Vulcano” word came from “Vulcan”, the Roman god of fire.
3) What is the study of volcanoes called?
Volcanology is the study of volcanoes.
4) Explain the occurrence of volcanoes.
The rigid lithosphere is divided into 16 larger and numerous smaller plates, according to plate tectonics theory. All of these plates are in slow motion. Volcanoes generally exist where tectonic plates are converging or diverging. The majority of them are found underwater. In the Mid-Atlantic Ridge, volcanoes were formed from diverging tectonic plates. On the other hand, volcanoes in the Pacific Ring of Fire were formed by converging tectonic plates. They can also be created from where there is thinning and stretching of the crust’s plates. Two such examples are the Rio Grande Rift and the East African Rift. Volcanoes usually do not exist where two tectonic plates slip past one another.
5) What are the three types of volcanic eruptions?
Eruption types are divided into phreatic, pragmatic and phreatomagmatic eruptions. High viscosity magma with a high amount of dissolved gas generates intense explosive eruptions. Low viscosity magma with a low quantity of dissolved gases causes comparatively gentle effusive eruptions.
Phreatomagmatic eruptions are produced by the activity of rising magma with groundwater. They are propelled by the resulting accelerated buildup of pressure in the extremely heated groundwater.
Phreatic eruptions are created by the superheating of groundwater that is exposed to hot magma or rock. They are different from phreatomagmatic eruptions because the exploded material is all country-rock, no magma is ejected.
6) Where do the majority of volcanoes exist?
About 75 percent of the Earth’s active volcanoes are located around the ring of fire (25,000-mile long). It is a horseshoe-shaped area that extends from the Southern point of South America across North America’s west coast, along the Bering Sea to Japan and ending at New Zealand.
7) How many volcanoes are there in India?
India has six volcanoes, including the only active one, “Barren Islands volcano”. In fact, it is the only confirmed live volcano in South Asia. The first recorded witness of its eruption dates back to 1787.
8) What are the dangerous consequences of volcanic eruptions?
Volcanic explosions pose many hazards apart from lava flows. Massive eruptions can alter atmospheric temperature as sulfuric acid droplets and ash block the Sun, which cool the troposphere. Throughout history, huge volcanic explosions have been accompanied by volcanic winters, which have paved the way for catastrophic famines. Volcanic eruptions are followed by pyroclastic flows. It is a mix of ash, high-speed toxic gases and avalanches of hot rocks. Likewise, volcanic mudflows known as lahars can be devastating. These fast-moving waves of debris and mud can flow down the flanks of a volcano, engulfing entire towns. Volcanic ash is another serious threat to nature. It consists of sharp bits of rocks and volcanic glass, smaller than two millimetres across. The ash generates as the gases in the rising magma enlarge, disintegrating the cooling rocks as they explode from the volcano’s mouth. It causes breathing problems, and it is heavy and multiplies quickly. Removal of ash is a serious challenge post-eruption.
9) What happened in Pompeii and Herculaneum in A.D. 79?
Volcanic eruptions are followed by pyroclastic flows. It is a mix of ash, high-speed toxic gases and avalanches of hot rocks. Such a phenomenon was the primary reason for wiping out the entire population of Herculaneum and Pompeii when Mount Vesuvius exploded in A.D. 79.
10) Which was the most catastrophic volcanic eruption in recorded history?
The most catastrophic volcanic activity in recorded history was the 1815 eruption of Mount Tambora in Indonesia. The explosion was one of the strongest ever recorded and created a crater (caldera) 6.4 km across and more than 1.09 km deep. A superheated wave of hot gas and ash shot 45 km into the sky, creating countless pyroclastic flows when it erupted.
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Practice Questions
1) What is the difference between a volcano and a mountain?
2) Which is the largest active volcano on the Earth?
3) Which country has the most number of active volcanoes?
4) Which is the world’s smallest active volcano?
5) Which is the hottest volcano on the Earth?
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