Galapagos shield volcanoes are some of the most active volcanoes in the world and constitute one of the most widespread volcano types in the ocean basins and on other planets. The internal plumbing, the mechanisms of magma migration, and the role of deformation in the evolution of Galapagos-type shield volcanoes are all poorly known, particularly in their type locality. The state of strain within the volcanoes and the emplacement of magma will be monitored through GPS geodetic and microgravity surveys at 51 stations at Fernandina and Sierra Negra volcanoes. After the initial deployment, the GPS networks will be reoccupied annually for two years to measure surface response to active subsurface processes and any eruptive activity. Microgravity measurements will also be carried out at the same stations each year, in order to detect changes in the gravity signal related to internal mass redistribution. This integrated investigation will address: 1) the origin of the characteristic morphology of Galapagos-type shields, 2) the mechanisms of caldera collapse, 3) the strain associated with emplacement of magma, 4) the long-term space accommodation from repeated dike intrusions, and 5) the geometry of magmatic intrusions underlying calderas. The results from this study should provide data useful in distinguishing between competing and poorly-constrained models of volcano evolution, and will greatly increase our understanding of the internal structure and active processes associated with morphologic and eruptive styles of Galapagos volcanism
