Continuous GPS data from Taal and Mayon volcanoes in the Philippines exhibit deformation patterns consistent with inflation and deflation of a point source centered approximately under their respective craters at depths of two to five km. These data, coupled with seismic and other ancillary data sets, are being used to investigate sizes, shapes and temporal evolution of the deformation sources. Both hydrothermal and magmatic fluid flux are expected to generate oscillatory inflation and deflation or "volcanic unrest" like that observed at Taal volcano [Lowry et al., 2001], so I am investigating whether space-time dependence of deformation can indicate source process as well as geometry of the source through time (in collaboration with Michael Hamburger and Beth Bartel at Indiana University [e.g., Bartel et al., 2003]).