A volcano is an opening or fissure in the Earth’s surface through which molten rock, known as magma, along with gases and ash, is expelled. The process by which magma is transported from the Earth’s interior to its surface is referred to as “vulcanicity” or volcanic activity.
Distribution of Volcanoes
| Zone | Extent | Cause | Examples |
|---|---|---|---|
| Circum-Pacific Belt | Includes volcanoes along the eastern and western coastal regions, island arcs near East Asia, and small volcanic islands in the Pacific Ocean. | Volcanism is linked to the interaction of the Pacific, Juan de Fuca, Cocos, Indian-Australian, Nazca, North American, and Philippine plates. | Fujiyama (Japan), Kadovar (Papua New Guinea), Mayon (Philippines) |
| Mid-Continental Belt | Covers volcanoes in the Alpine mountain range, the Mediterranean region, and the East African Rift Valley. | Results from the collision of the Eurasian, Indo-Australian, and African plates. | Vesuvius, Stromboli, Kilimanjaro |
| Mid-Atlantic Ridge | Includes volcanoes along the Mid-Atlantic Ridge. | Formed as the North American and Eurasian plates diverge, causing fissure eruptions. | Active volcanic zones in Iceland |
| Intra-plate Volcanoes | Found within tectonic plates, far from their boundaries. | Associated with mantle hotspots beneath the plate interiors. | Hawaii Islands in the Pacific Ocean |
Hotspots
A hotspot is a region above a mantle plume where volcanic activity occurs.
- Mantle Plume: A zone beneath the Earth’s crust containing magma significantly hotter than its surroundings.
- High temperatures in the plume cause the crust to melt and thin, leading to volcanic eruptions.
- Lava from these hotspots is alkaline, and the resulting crust is termed Ocean Island Basalt.
- Hotspots can create large volcanic provinces, such as the Deccan Traps in India, formed during the Late Cretaceous period when the Indian Plate passed over the Reunion Hotspot.
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