Large igneous province

In geology, a large igneous province (LIP) is an extremely large accumulation of igneous rocks, including plutonic rocks (intrusive) or volcanic rock formations (extrusive), arising when hot magma extrudes from inside the Earth and flows out. The source of many or all LIPs is variously attributed to mantle plumes or to processes associated with plate tectonics. Types of LIPs can include large volcanic provinces (LVP), created through flood basalt, and large plutonic provinces (LPP). Rampino and Stothers (1988) cite eleven distinct flood-basalt episodes - occurring in the past 250 million years - which created volcanic provinces and plateaus and coincided with mass extinctions. However, more flood basalts have been recognized, such as the large Ontong Java Plateau, and the medium-sized Chilcotin Group, though the latter may be linked to the Columbia River Basalt Group. Formation depends on a range of factors, such as continental configuration, latitude, volume, rate, duration of eruption, style and setting (continental vs. oceanic), the pre-existing climate state, and the biota resilience to change.

In 1992 researchers first used the term large igneous province to describe very large accumulations—areas greater than 100,000 square kilometers (approximately the area of Iceland)—of mafic igneous rocks that were erupted or emplaced at depth within an extremely short geological time interval: a few million years or less. Mafic, basalt sea floors and other geological products of 'normal' plate tectonics were not included in the definition.

The definition of LIP has been expanded and refined, and is still a work in progress. LIP is now frequently also used to describe voluminous areas of, not just mafic, but all types of igneous rocks. Sub-categorization of LIPs into large volcanic provinces (LVP) and large plutonic provinces (LPP), and including rocks produced by normal plate tectonic processes, has been proposed.

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