Calderas are huge topographic depressions formed by large volcanic eruptions. They sometimes experience an inflation of their floor of up to a kilometer, caused by magma injection. This process, dubbed ‘caldera resurgence,’ remains one of the least understood in volcanology. Researchers now show that non-erupted magma left after the caldera-forming eruption behaves as a ‘rubber sheet’ that inhibits the rise of the newly injected magma.