Giant volcanic eruptions could be triggered by the buoyancy of magma alone, report two independent studies published online this week in Nature Geoscience. Although smaller, more frequent eruptions are known to often be triggered by the injection of new magma into a magma chamber, the trigger for larger eruptions has remained enigmatic.

Magma is buoyant because it is hot compared with the Earth’s cool crust that hosts the magma chamber beneath a volcano. Luca Caricchi and colleagues and Wim Malfait and colleagues used computer models and laboratory experiments, respectively, to show that the pressure placed on magma chamber walls within a volcano by buoyant magma can be sufficient to trigger a giant eruption. Specifically, if magma is gradually added to a large magma chamber over a period of hundreds of thousands to millions of years, the build-up of pressure can cause the magma chamber roof to collapse, generating a giant eruption similar to those that have previously occurred at Yellowstone, USA.

In an accompanying News and Views article, Mark Jellinek writes that the results imply that “rare, giant super-eruptions and smaller, more frequent events reflect a transition in the essential driving forces for volcanism.”