The vigor and size of volcanic eruptions depend on what happens in magma reservoirs in the Earth’s crust. When magmatic activity occurs within continental areas, large reservoirs of viscous, gas-rich magma can be generated and cataclysmically discharged into the atmosphere during explosive supereruptions. As currently understood, large pools of explosive magma are produced by extracting interstitial liquid from long-lived “crystal mushes” (magmatic sponges containing >50 vol% of crystals) and collecting it in unstable liquid-dominated lenses.