Tree-ring (super 14) C links seismic swarm to CO (sub 2) spike at Yellowstone, USA

Mechanisms to explain swarms of shallow seismicity and inflation-deflation cycles at Yellowstone caldera (western United States) commonly invoke episodic escape of magma-derived brines or gases from the ductile zone, but no correlative changes in the surface efflux of magmatic constituents have ever been documented. Our analysis of individual growth rings in a tree core from the Mud Volcano thermal area within the caldera links a sharp approximately 25% drop in (super 14) C to a local seismic swarm in 1978. The implied fivefold increase in CO (sub 2) emissions clearly associates swarm seismicity with upflow of magma-derived fluid and shows that pulses of magmatic CO (sub 2) can rapidly traverse the 5-km-thick brittle zone, even through Yellowstone's enormous hydrothermal reservoir. The 1978 event predates annual deformation surveys, but recognized connections between subsequent seismic swarms and changes in deformation suggest that CO (sub 2) might drive both processes.