Professor Emeritus, Dartmouth College, Hanover, New Hampshire. Definition: A volcanic eruption occurs when magma is released from a volcano. Shield volcanoes are made from. At rift zones, or divergent margins, shield volcanoes tend to form as two oceanic plates pull slowly apart and magma effuses upward through the gap. Volcanoes figure prominently in the mythology of many peoples who have learned to live with eruptions, but science was late in recognizing the important role of volcanism in the evolution of Earth. This diagram has all the parts of a volcano clearly labelled. One can say, for example, that large lava flows erupt from Mauna Loa volcano in Hawaii, referring here to the vent; but one can also say that Mauna Loa is a gently sloping volcano of great size, the reference in this case being to the landform. The most spectacular eruptions consist of violent explosions that blast great clouds of gas-laden debris into the atmosphere. (Physical Geography) a mountain formed from volcanic material ejected from a vent in a central crater. They are formed from layers of ash and lava. An island is a solitary mountain formed by volcanic activity. Volcanoes. Most volcanoes are … For example, Mount Kenya is an extinct volcano. – an opening in the earth’s crust through which material is forced upwards during a volcanic eruption. Scroll down to find out more. the point where three tectonic plates meet. During an episode of activity, a volcano commonly displays a distinctive pattern of behavior. With its striking steep slopes built up of layers of ash and lava, Mount Fuji is a classic stratovolcano. Volcanoes and thermal fields that have been active during the past 10,000 years. The most recent lava flow was erupted from the summit crater and flowed to the west. Mount Fuji in Japan. What does the inside of a volcano look like and how close can someone get to a live volcano? A volcanic eruption is an awesome display of Earth’s power. Some burst to life in explosive eruptions, like the 1991 eruption of Mount Pinatubo, and others burp rivers of lava … Yet, while eruptions are spectacular to watch, they can cause disastrous loss of life and property, especially in densely populated regions of the world. A volcano is an opening in the earth's crust through which magma, ash and gas erupt. The layers of ash and lava are built up over successive eruptions. Geography; Tectonic Activity; Volcanoes; Volcanoes; Volcanoes. But each volcano is different. Volcano definition, a vent in the earth's crust through which lava, steam, ashes, etc., are expelled, either continuously or at irregular intervals. Yet, while eruptions are spectacular to watch, they can cause disastrous loss of life and property, especially in densely populated regions of the world. BSL Geography Glossary - Volcanic Eruption - definition. Its most recent eruption was in 1994, when it and another vent, Tavurvur, forced the city of Rabaul to be temporarily abandoned and the local administrative centres of East New Britain Province to be moved to a new capital, Kokopo. Swarms of small earthquakes, which may be caused by a rising plug of dense, viscous magma oscillating against a sheath of more-permeable magma, may also signal volcanic eruptions, especially explosive ones. The study of volcanoes and their products is known as volcanology, but these phenomena are not the realm of any single scientific discipline. Articles from Britannica Encyclopedias for elementary and high school students. Mauna Loa typifies a shield volcano, which is a huge, gently sloping landform built up of many eruptions of fluid lava. About Us. In more violent eruptions, the magma conduit is cored out by an explosive blast, and solid fragments are ejected in a great cloud of ash-laden gas that rises tens of thousands of metres into the air. 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