Friction is commonly thought to be controlled by processes in small asperities between two sliding surfaces. These asperities hold a large fraction of the mating surfaces apart and therefore dramatically increase the local contact stresses. In this study, a special two-axis nanoindentation system was used to examine the mechanics of deformation of micron-scale asperity contacts by sliding a spherical diamond indenter with a radius of ~2 um over a flat plate of fused silica under a combination of normal and transverse loading. The nanoindentation system is comprised of two independently controlled nanoindentation actuators oriented transverse to each other in such a way that the forces and displacements of each could be independently controlled and monitored. The two actuators could also be operated in continuous stiffness mode (CSM) to measure both the normal and transverse stiffnesses and the degree of energy dissipation during sliding through the phase shift of the CSM load and displacement oscillations. Tests were conducted by holding the normal force on the spherical indenter constant and ramping the lateral force at a constant rate. The extent of plasticity during sliding was varied by controlling the magnitude of the normal load so as to produce either a perfectly elastic contact or a combination of elastic and plastic deformation. Atomic force microscopy (AFM) was used to image the scratch tracks and confirm some of the observations from the nanoindentation data. Results are presented and discussed in terms of prevailing ideas on the mechanistic processes that control friction in single asperity contacts, with special emphasis on differences between purely elastic contact and contact that involves both elastic and plastic deformation.