The spatio-temporal evolution of a propagating magma-filled crack was estimated from inversion of Global Positioning System (GPS) data, tiltmeters, and leveling. The dike opened at a maximum rate of 50 millimeters per day and had a peak magma flux of 2 x 10(6) cubic meters per day. Although the spatial resolution was limited, slow upward propagation was resolved during the 9-day-long intrusion. In contrast, the earthquakes migrated rapidly upward during the first 12 hours of the swarm, and nearly all of the seismic energy was released in the first 2 days. Comparison of inversion results with accurate hypocenter locations will lead to improved understanding of magma transport through the brittle crust and of the causes of volcanic seismicity.