Image from: NASA’s Galileo spacecraft
No signs of tectonism have been seen on the surface of Callisto. The surface of Callisto was carefully examined for types of faulting and fracture. These would have provided evidence of the kind of stress (pushing and shoving) which the crust of Callisto has undergone through time.
Examination of the surface of Callisto shows only that there has been gradual slumping, or “relaxation” of the craters, and what is termed “sublimation-erosion” of the surface.
This type of surface is perhaps unique in the solar system. It is certainly a different type of surface that either that of Ganymede or Europa. (The other major moon of Jupiter, Io has a more conventional form of volcanism.) The difference has to do with the lack of processes in the interior of Callisto.