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Volcanism may be defined as the eruption of molten rock (magma) onto the surface of the earth. A volcano is a way through which magma and gases come out. The Magma that gets to the surface is known as lava.
1. Why and where do volcanos form?
Volcanism is the outcome of a planet releasing its inner heat. Volcanos can be seen where rock near the planet’s surface becomes heated sufficiently to melt. On Earth, this usually occurs in relation to plate boundaries.
Where two plates move far away, such as at mid-ocean volcanic ridges, material from Earth’s interior slowly increases up, melts when it gets to lower pressures, and completes the gap.
Where one plate moves by subduction under another, chambers of magma may be seen. These magma bodies nourish the volcanic islands that denote subduction zones.
Although most volcanic activity occurs at plate boundaries, volcanism also can take place within the plate interiors at hotspots. Hotspots are thought to be prepared large plumes‖ of highly hot material enhanced from deep in Earth’s inner. The hot material enhances slowly, occasionally melting as it achieves lower pressures near Earth’s surface. When the material breaks out it forms huge lava flows of fine-grained dark volcanic rock and basalt. The broad, gentle shield volcanos of Hawai’i result from a hotspot.
2. Meaning of Volcano
The fact that Earth has volcanoes tells us that Earth’s inner is circulating and is hot (sufficient to melt).
Earth is releasing heat; volcanos are one option to release heat. The pattern of issuing of volcanos on Earth provides us with the idea that Earth’s outer surface is split into plates; the chains of volcanos related to mid-ocean ridges and subduction zones denote the plate edges.
Other planets have volcanic features some recently active telling geologists that they, too, are losing heat from their interiors and that there is circulation. However, these planets do not display the pattern that Earth’s volcanos do. Figure showing the relation of Plate tectonic and Volcanism.
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