From some of the first analyses of Pioneer Venus data, volcanic rises such as Beta Regio were recognized for their domal topography, extensional tectonics, volcanic constructs, and gravity anomalies suggestive of sub-lithospheric compensation [ McGill et al., 1981; Esposito et al., 1982]. Noting that such rises were common features of Venus, Morgan and Phillips [1983] showed that over 90% of Venus' surface could be explained by topographic variations due to thinning or thickening of the thermal lithosphere, and suggested that topography and tectonics on Venus were primarily related to plume-like regions of upwelling in the deep mantle. Although questions such as to the details of buoyancy forces supporting rise topography remain to be fully answered, there is a general consensus that volcanic rises are the result of deep-seated upwellings in the mantle of Venus. The more relevant questions relate to the present degree of activity of volcanic rises and the mantle beneath them.