This article is about the process that forms volcanoes and igneous rocks. For the 18th century geological theory, see Plutonism.
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a vent.[1] It includes all phenomena resulting from and causing magma within the crust or mantle of the body, to rise through the crust and form volcanic rocks on the surface. Magmas, that reach the surface and solidify, form extrusive landforms.[2]
Plate tectonics map with volcano locations indicated with red circles
Non-viscous lava during an effusive eruption of Kīlauea
Magma from the mantle or lower crust rises through the crust towards the surface. If magma reaches the surface, its behavior depends on the viscosity of the molten constituent rock. Viscous (thick) magma produces volcanoes characterised by explosive eruptions, while non-viscous (runny) magma produce volcanoes characterised by effusive eruptions pouring large amounts of lava onto the surface.
In some cases, rising magma can cool and solidify without reaching the surface. Instead, the cooled and solidified igneous mass crystallises within the crust to form an igneous intrusion. As magma cools the chemicals in the crystals formed are effectively removed from the main mix of the magma (by a process known as fractional crystallization), so the chemical content of the remaining magma evolves as it solidifies slowly. Fresh unevolved magma injections can remobilise more evolved magmas, allowing eruptions from more viscous magmas.
Cross-section through a stratovolcano (vertical scale is exaggerated):
Large magma chamber
Bedrock
Conduit (pipe)
Base
Sill
Dike
Layers of ash emitted by the volcano
Flank
Layers of lava emitted by the volcano
Throat
Parasitic cone
Lava flow
Vent
Crater
Ash cloud
Volcanoes are places where magma reaches the planet's surface. The type of volcano depends on the location of the eruption and the consistency of the magma.
Earthquakes are generally associated with plate tectonic activity, but some earthquakes are generated as a result of volcanic activity [3](though that itself is ultimately driven by the same forces).
The amount of gas and ash emitted by volcanic eruptions has a significant effect on the Earth's climate. Large eruptions correlate well with some significant climate change events.[5]
When magma cools it solidifies and forms rocks. The type of rock formed depends on the chemical composition of the magma and how rapidly it cools. Magma that reaches the surface to become lava cools rapidly, resulting in rocks with small crystals such as basalt. Some of this magma may cool extremely rapidly and will form volcanic glass (rocks without crystals) such as obsidian. Magma trapped below ground in thin intrusions cools more slowly than exposed magma and produces rocks with medium-sized crystals. Magma that remains trapped in large quantities below ground cools most slowly resulting in rocks with larger crystals, such as granite and gabbro.
Existing rocks that come into contact with magma may be melted and assimilated into the magma. Other rocks adjacent to the magma may be altered by contact metamorphism or metasomatism as they are affected by the heat and escaping or externally-circulating hydrothermal fluids.
Volcanism is not confined only to Earth, but is thought to be found on any body having a solid crust and fluid mantle. Evidence of volcanism should still be found on any body that has had volcanism at some point in its history. Volcanoes have indeed been clearly observed on other bodies in the Solar System – on some, such as Mars, in the shape of mountains that are unmistakably old volcanoes (most notably Olympus Mons), but on Io actual ongoing eruptions have been observed. It can be surmised that volcanism exists on planets and moons of this type in other planetary systems as well. In 2014, scientists found 70 lava flows which formed on the Moon in the last 100 million years.[6]
^"Cooling Planets: Some Background: What is volcanism?" (PDF). The Lunar and Planetary Institute, Department of Education and Public Outreach. 2006. p. 4. (PDF) from the original on 2013-08-01. Retrieved 2012-10-14.
^Leong, Goh Cheng (1995-10-27). Certificate Physics And Human Geography; Indian Edition. Oxford University Press. p. 20. ISBN978-0-19-562816-6.
^Watson, John; Watson, Kathie (January 7, 1998). "Volcanoes and Earthquakes". United States Geological Survey. from the original on March 26, 2009. Retrieved May 9, 2009.
^ abNemzer, J. . Archived from the original on 2012-11-01. Retrieved 2012-11-03.
^Robock, Alan (2000). "Volcanic eruptions and climate". Reviews of geophysics 38 (2): 191-219. doi:10.1029/1998RG000054
^"Recent volcanic eruptions on the moon". sciencemag.org. 12 October 2014. Retrieved 6 May 2018.
External links
Wikimedia Commons has media related to Volcanism.
"Glossary of Volcanic Terms". G. J. Hudak, University of Wisconsin Oshkosh, 2001. Retrieved 2010-05-07.
Crumpler, L. S., and Lucas, S. G. (2001). (PDF). Volcanology in New Mexico. New Mexico Museum of Natural History and Science Bulletin. 18: 5–15. Archived from the original (PDF) on 2007-03-21. Retrieved 2010-04-28.{{cite journal}}: CS1 maint: uses authors parameter (link)
February 04, 2023
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This article is about the process that forms volcanoes and igneous rocks For the 18th century geological theory see Plutonism Volcanism vulcanism or volcanicity is the phenomenon of eruption of molten rock magma onto the surface of the Earth or a solid surface planet or moon where lava pyroclastics and volcanic gases erupt through a break in the surface called a vent 1 It includes all phenomena resulting from and causing magma within the crust or mantle of the body to rise through the crust and form volcanic rocks on the surface Magmas that reach the surface and solidify form extrusive landforms 2 Plate tectonics map with volcano locations indicated with red circles Contents 1 Volcanic processes 2 Driving forces of volcanism 3 Aspects of volcanism 3 1 Volcanoes 3 2 Intrusions 3 3 Earthquakes 3 4 Hydrothermal vents 3 5 Volcanic winter 4 Forming rocks 5 Volcanism on other bodies 6 See also 7 References 8 External linksVolcanic processes Edit Non viscous lava during an effusive eruption of Kilauea Magma from the mantle or lower crust rises through the crust towards the surface If magma reaches the surface its behavior depends on the viscosity of the molten constituent rock Viscous thick magma produces volcanoes characterised by explosive eruptions while non viscous runny magma produce volcanoes characterised by effusive eruptions pouring large amounts of lava onto the surface In some cases rising magma can cool and solidify without reaching the surface Instead the cooled and solidified igneous mass crystallises within the crust to form an igneous intrusion As magma cools the chemicals in the crystals formed are effectively removed from the main mix of the magma by a process known as fractional crystallization so the chemical content of the remaining magma evolves as it solidifies slowly Fresh unevolved magma injections can remobilise more evolved magmas allowing eruptions from more viscous magmas Driving forces of volcanism EditMain article Plate tectonics Three types of plate boundary Movement of molten rock in the mantle caused by thermal convection currents coupled with gravitational effects of changes on the earth s surface erosion deposition even asteroid impact and patterns of post glacial rebound drive plate tectonic motion and ultimately volcanism Aspects of volcanism EditVolcanoes Edit Main article Volcano Cross section through a stratovolcano vertical scale is exaggerated Large magma chamberBedrockConduit pipe BaseSillDikeLayers of ash emitted by the volcanoFlankLayers of lava emitted by the volcanoThroatParasitic coneLava flowVentCraterAsh cloud Volcanoes are places where magma reaches the planet s surface The type of volcano depends on the location of the eruption and the consistency of the magma Further information Types of volcanic eruptions Intrusions Edit Types of Intrusion Laccolithsmall DikePluton BatholithDikeSillPipe Volcanic neckLopolith Main article Intrusion See also Pluton emplacement These are formed where magma pushes between existing rock intrusions can be in the form of batholiths dikes sills and layered intrusions Earthquakes Edit Main article Volcano tectonic earthquake Earthquakes are generally associated with plate tectonic activity but some earthquakes are generated as a result of volcanic activity 3 though that itself is ultimately driven by the same forces Hydrothermal vents Edit Main article Hydrothermal vent These are formed where water interacts with volcanism 4 These include geysers fumaroles hotsprings and mudpots they are often used as a source of geothermal energy 4 Volcanic winter Edit Main article Volcanic winter The amount of gas and ash emitted by volcanic eruptions has a significant effect on the Earth s climate Large eruptions correlate well with some significant climate change events 5 Forming rocks EditMain articles Igneous rock and Metamorphic rock When magma cools it solidifies and forms rocks The type of rock formed depends on the chemical composition of the magma and how rapidly it cools Magma that reaches the surface to become lava cools rapidly resulting in rocks with small crystals such as basalt Some of this magma may cool extremely rapidly and will form volcanic glass rocks without crystals such as obsidian Magma trapped below ground in thin intrusions cools more slowly than exposed magma and produces rocks with medium sized crystals Magma that remains trapped in large quantities below ground cools most slowly resulting in rocks with larger crystals such as granite and gabbro Existing rocks that come into contact with magma may be melted and assimilated into the magma Other rocks adjacent to the magma may be altered by contact metamorphism or metasomatism as they are affected by the heat and escaping or externally circulating hydrothermal fluids Volcanism on other bodies EditMain articles Volcanism on Io Volcanism on Venus Volcanism on Mars Volcanism on the Moon and Geology of Vesta See also Geology of solar terrestrial planets Volcanism is not confined only to Earth but is thought to be found on any body having a solid crust and fluid mantle Evidence of volcanism should still be found on any body that has had volcanism at some point in its history Volcanoes have indeed been clearly observed on other bodies in the Solar System on some such as Mars in the shape of mountains that are unmistakably old volcanoes most notably Olympus Mons but on Io actual ongoing eruptions have been observed It can be surmised that volcanism exists on planets and moons of this type in other planetary systems as well In 2014 scientists found 70 lava flows which formed on the Moon in the last 100 million years 6 The internal structure of the inner planets See also EditBimodal volcanism Cryovolcanism Hotspot Magmatism Prediction of volcanic activity Seafloor spreading Volcanic arc Volcano VolcanologyReferences Edit Cooling Planets Some Background What is volcanism PDF The Lunar and Planetary Institute Department of Education and Public Outreach 2006 p 4 Archived PDF from the original on 2013 08 01 Retrieved 2012 10 14 Leong Goh Cheng 1995 10 27 Certificate Physics And Human Geography Indian Edition Oxford University Press p 20 ISBN 978 0 19 562816 6 Watson John Watson Kathie January 7 1998 Volcanoes and Earthquakes United States Geological Survey Archived from the original on March 26 2009 Retrieved May 9 2009 a b Nemzer J Geothermal heating and cooling Archived from the original on 2012 11 01 Retrieved 2012 11 03 Robock Alan 2000 Volcanic eruptions and climate Reviews of geophysics 38 2 191 219 doi 10 1029 1998RG000054 Recent volcanic eruptions on the moon sciencemag org 12 October 2014 Retrieved 6 May 2018 External links Edit Wikimedia Commons has media related to Volcanism Glossary of Volcanic Terms G J Hudak University of Wisconsin Oshkosh 2001 Retrieved 2010 05 07 Crumpler L S and Lucas S G 2001 Volcanoes of New Mexico An Abbreviated Guide For Non Specialists PDF Volcanology in New Mexico New Mexico Museum of Natural History and Science Bulletin 18 5 15 Archived from the original PDF on 2007 03 21 Retrieved 2010 04 28 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint uses authors parameter link Retrieved from https en wikipedia org w index php title Volcanism amp oldid 1137350079, wikipedia, wiki, book, books, library,
