When most people think about volcanoes, they probably envision a cone-shaped mountain with ash and gas emitted from its summit like Semeru (Java) and Fuego (Guatemala) volcanoes, or the rivers of lava extruded from Hawaiian or Icelandic eruptions. However, the largest explosive volcanic eruptions (LEVEs) known on Earth are very different from those fairly common ones. Such LEVEs erupt massive amounts of fragmented magma (not lava), form gigantic craters (calderas) instead of mountains, generate fast-moving lethal ‘flows’ of incandescent material, drastically modify the landscape over extensive areas, have devastating local and regional impacts, and could possibly even affect hemispheric or global climate.