About 10 years ago, Jurgen Neuberg, a volcanologist at the University of Leeds, and his colleagues discovered a subtle oversight in the theory of seismic-wave propagation.1 Their calculations indicated that seismic waves traveling through a bubbly liquid should attenuate more quickly than anyone had imagined. As their thinking went, the oscillating pressure field of a passing wave should continually shift the thermodynamic equilibrium between the bubble and liquid phases: As pressure rises, gas molecules should diffuse from the bubbles to the liquid, and vice versa as pressure falls. The cyclical contraction and expansion of the bubbles would dissipate substantial seismic energy as heat.
Neuberg and his coworkers were trying to answer a specific question: How far can seismic waves travel inside the magma-filled chutes of a volcano? But the potential implications of their finding were broad. Geophysicists typically image Earth’s upper crust by detecting reflections of seismic waves in...
