Over the past decade, shipboard surveys of the Easter and Juan Fernandez microplates along the East Pacific Rise have revealed the complex bathymetric and magnetic seafloor fabrics that characterize the interiors and boundaries of oceanic microplates (Fig. 2). Detailed kinematic studies of both of these plates suggest that their distinctive patterns of magnetic anomalies and bathymetry result from rapid rotation of the microplates about nearby vertical axes (e.g. Naar and Hey, 1991; Larson et al., 1992; Rusby, 1992). The recently proposed roller-bearing model for the kinematic evolution of oceanic microplates has drawn the various observational and kinematic studies of the Easter, Juan Fernandez, and other microplates into a promising conceptual framework [ Schouten et al., 1993]. In this model, a microplate behaves as a rigid or nearly rigid roller bearing whose rotation is directly proportional to its size and is caused by shear tractions imposed by the adjacent major plates (Fig. 2). The predicted rotation rate is twice that required by floating block models, in which basal shear drives the rotation. Larson et al. [1992] and Schouten et al. [1993] demonstrate that microplate rotation rates measured from magnetic anomalies created along the boundaries of the Juan Fernandez and Easter microplates agree well with those predicted by the roller-bearing model, allowing basal shear models to be excluded at a high confidence level. Whether such a model applies to rotating crustal blocks in zones of continental deformation is unknown. Unlike oceanic crust, which has numerous space-time markers ( e.g. magnetic lineations) that record total rotations, continental block rotations must be inferred from sparse and often less precise paleomagnetic and seismologic observations. Work to date [e.g. Jackson and Molnar, 1990; England and Wells, 1991] supports basal shear models more so than edge-driven models; however, improved observational constraints such as high precision space geodetic measurements are essential for further progress.