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constructive margin




In plate tectonics, the boundary between two lithospheric plates (see lithosphere), which are moving apart and new crust is being formed. Constructive margins are associated with shallow-focus earthquakes, high heat flow and eruptions and injections of basalt. Characteristically they produce mid-ocean ridges, but Iceland is an example where a mid-ocean ridge has surfaced above sea-level. See also destructive margin.


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   • GEOLOGY AND PLANETARY SCIENCE