Large igneous province

A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive (sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about the causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems. 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 but are not generally accepted. Some LIPs are geographically intact, such the basaltic Deccan Traps in India, while others have been fragmented and separated by plate movements, like the Central Atlantic Magmatic Province (CAMP)—parts of which are found in Brazil, eastern North America, and north-western Africa.