Editing Plate tectonics (section)

== Types of plate boundaries ==
{{Main|List of tectonic plate interactions}}

Three types of plate boundaries exist,{{sfn|Meissner|2002|p=100}} characterized by the way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are:<ref name="platetectonics.com">{{Cite web |title=Plate Tectonics: Plate Boundaries |url=http://www.platetectonics.com/book/page_5.asp |url-status=dead |archive-url=https://web.archive.org/web/20100616062513/http://www.platetectonics.com/book/page_5.asp |archive-date=16 June 2010 |access-date=12 June 2010 |publisher=platetectonics.com}}</ref><ref name="usgs.understanding.com">{{Cite web |title=Understanding plate motions |url=http://pubs.usgs.gov/gip/dynamic/understanding.html |url-status=live |archive-url=https://web.archive.org/web/20190516204054/https://pubs.usgs.gov/gip/dynamic/understanding.html |archive-date=16 May 2019 |access-date=12 June 2010 |publisher=United States Geological Survey}}</ref>

[[File:Continental-continental constructive plate boundary.svg|thumb|upright=1.15|Divergent boundary]]
* ''[[Divergent boundary|Divergent boundaries]]'' (''constructive boundaries'' or ''extensional boundaries''). These are where two plates slide apart from each other. At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new [[oceanic basin|ocean basin]], e.g. the [[Mid-Atlantic Ridge]] and [[East Pacific Rise]]. As the ocean plate splits, the ridge forms at the spreading center, the ocean basin expands, and finally, the plate area increases causing many small volcanoes and/or shallow earthquakes. At zones of continent-to-continent rifting, divergent boundaries may cause new ocean basin to form as the continent splits, spreads, the central rift collapses, and ocean fills the basin, e.g., the [[East African Rift]], the [[Baikal Rift Zone|Baikal Rift]], the [[West Antarctic Rift]], the [[Rio Grande Rift]].

[[File:Continental-continental destructive plate boundary.svg|thumb|upright=1.15|Convergent boundary]]
* ''[[Convergent boundary|Convergent boundaries]]'' (''destructive boundaries'' or ''active margins'') occur where two plates slide toward each other to form either a [[subduction]] zone (one plate moving underneath the other) or a [[continental collision]]. 
:Subduction zones are of two types: ocean-to-continent subduction, where the dense oceanic lithosphere plunges beneath the less dense continent, or ocean-to-ocean subduction where older, cooler, denser oceanic crust slips beneath less dense oceanic crust. Deep marine trenches are typically associated with subduction zones, and the basins that develop along the active boundary are often called "foreland basins". 
:Earthquakes trace the path of the downward-moving plate as it descends into asthenosphere, a trench forms, and as the subducted plate is heated it releases volatiles, mostly water from [[serpentinite|hydrous minerals]], into the surrounding mantle. The addition of water lowers the melting point of the mantle material above the subducting slab, causing it to melt. The magma that results typically leads to volcanism.<ref name="H2O">{{Cite journal |last1=Grove |first1=Timothy L. |last2=Till |first2=Christy B. |last3=Krawczynski |first3=Michael J. |date=8 March 2012 |title=The Role of H2O in Subduction Zone Magmatism |url=https://www.researchgate.net/publication/235935490 |journal=[[Annual Review of Earth and Planetary Sciences]] |volume=40 |issue=1 |pages=413–39 |bibcode=2012AREPS..40..413G |doi=10.1146/annurev-earth-042711-105310 |access-date=14 January 2016}}</ref> 
:At zones of ocean-to-ocean subduction a deep trench forms in an arc shape. The upper mantle of the subducted plate then heats and magma rises to form curving chains of volcanic islands e.g. the [[Aleutian Islands]], the [[Mariana Islands]], the [[Japan]]ese [[island arc]]. 
:At zones of ocean-to-continent subduction mountain ranges form, e.g. the [[Andes]], the [[Cascade Range]].
:At continental collision zones there are two masses of continental lithosphere converging. Since they are of similar density, neither is subducted. The plate edges are compressed, folded, and uplifted forming mountain ranges, e.g. [[Himalayas]] and [[Alps]]. Closure of ocean basins can occur at continent-to-continent boundaries.

[[File:Continental-continental conservative plate boundary opposite directions.svg|thumb|upright=1.15|Transform boundary]]
* ''[[Transform fault|Transform boundaries]]'' (''conservative boundaries'' or '' strike-slip boundaries'') occur where plates are neither created nor destroyed. Instead, two plates slide, or perhaps more accurately grind past each other, along [[transform fault]]s.  The relative motion of the two plates is either [[sinistral and dextral|sinistral]] (left side toward the observer) or [[sinistral and dextral|dextral]] (right side toward the observer). Transform faults occur across a spreading center. Strong earthquakes can occur along a fault. The [[San Andreas Fault]] in California is an example of a transform boundary exhibiting dextral motion.
* Other ''plate boundary zones'' occur where the effects of the interactions are unclear, and the boundaries, usually occurring along a broad belt, are not well defined and may show various types of movements in different episodes.