The largest eruptions on Earth

摘要

Large igneous provinces, are, as their name suggests, large; in fact they can be very large. For example, the Ontong-Java, Hikurangi and Manihiki plateaus have a combined areal extent of 3.5 Mkm~2 (an area larger than the Indian subcontinent), a crustal thickness of up to 30 km and an estimated volume of between 59 and 77 Mkm~3. But how, and over what period of time, are such vast volumes of extrusive and intrusive rock emplaced? (Fig. 8a,b). One answer is that large igneous provinces are the sites of the largest volcanic eruptions on Earth, and Scott Bryan and colleagues provide a review of the magnitude and nature of eruptions within them (Earth Science Reviews, 2010, v.102, pp.207-229). Estimating the scale of individual eruptions is not easy, however, as the products of an individual eruption can cover very wide areas. As these once continuous deposits are eroded into, buried or tectonically fragmented, a range of geological factors are needed to prove that now isolated outcrops were originally joined. Another difficulty is that with large scale silicic eruptions, there will be ignimbrites close to source but between 30 and 80 per cent of the erupted material might form co-ignimbrite ash clouds that may be deposited >1000 km downwind of the site of the eruption.