Volcanic bipolar disorder explained

摘要

Super-eruptions are among the most arresting volcanic phenomena preserved in the geological record. Over periods lasting days to weeks, single eruptions discharge enough ash, pumice and aerosols into the atmosphere to bury a large city to a depth of a few kilometres, with potentially severe consequences for Earth’s climate and global ecology1,2. These rare events are outside human experience, recurring only every few hundred thousand to a million years. Recent dramatic examples of explosive volcanism, such as the 2010 Eyjafjallaj?kull eruption in Iceland, the 1991 eruption of Mount Pinatubo or the 1980 eruption of Mount Saint Helens, pale in comparison. These relatively frequent events expel typically around 0.1% of the volume of material of a super-eruption over a similar period of time. The distinction between super-eruptions and smaller events is, however, more profound than a simple difference in total volume or eruption rate. Rather, there seem to be fundamental differences in the processes that trigger the two types of eruption. Writing in Nature Geoscience, Malfait et al.3 and Caricchi et al.4 use experiments and numerical models, respectively, to show that whereas frequent Pinatubo-sized eruptions are driven as a result of the supply of magma into nascent upper-crustal magma chambers, super-volcanic events are ultimately initiated as a consequence of the buoyancy of these chambers once they grow very large.