For an explanation, see the main splats page
The principles of volcanoes
- Volcanoes bring molten rock to the surface, erosion and weathering convert these rocks to sediments. If they are compressed or heated, sedimentary rocks change.
- A volcano erupts when magma gets close enough to the surface of the Earth to force its way out: when it erupts onto the surface, the molten rock is called lava.
- Volcanoes are of different types, determined by the sort of magma that is working its way to the surface, as the geochemistry influences the type of eruption.
- Volcanoes happen where plates are in contact, and also over 'hot spots' which can cause a chain of volcanoes as a plate moves over the hot spot.
- Many of the volcanic island chains in the Pacific Ocean are caused by a plate moving over a hot spot. Hawaii is probably the best-known example.
- Volcanic areas often have geysers, where groundwater is heated under pressure until it boils, pushes out overlying water, and then boils explosively.
- While volcanoes cause a great deal of local damage in the short term, they are very useful in long term because they bring valuable new minerals to the surface.
- Volcanoes produce more than lava flows: they also produce large clouds of ash and dust which can travel long distances, and large amounts of noxious gases.
- The form and shape of a volcano depends on the chemical composition of the magma which determines how it erupts.
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