Lips and Lips

It has been nearly 15 years since the term ‘large igneous province’ was introduced by Mike Coffin and Olaf Eldholm (1991, 1994). An umbrella term to include continental flood basalt provinces, oceanic plateaus, volcanic rifted margins and aseismic ridges, it rapidly entered common parlance even though it was, and remains, loosely defined. The key aspect of large igneous provinces (LIPs) is that they represent anomalously high magmatic fluxes. The magma is usually basaltic, but may be rhyolitic. They are large in area, covering many thousands if not millions of square kilometres, and they testify to unusual geological processes, involving large amounts of thermal energy. Where this energy comes from – deep within the Earth as a mantle plume, from a meteorite impact, or from sinking of dense roots from the base of the continental crust or lithosphere (‘delamination’) – is a matter of considerable debate. As will be seen from the papers in this issue of Elements, there is also debate about their environmental effects. Could the formation of such provinces cause the collapse of ecosystems, either by interrupting oceanic circulation systems or by releasing large masses of volcanic aerosols, and trigger mass extinctions? Certainly, the timing of LIPs and mass extinctions suggests some causality, but we do not, as yet, understand its nature.