What condition is likely to occur at a transform fault boundary?

At a transform fault boundary, the primary geological activity that occurs is the movement of tectonic plates sliding past each other laterally. This friction between the plates can cause significant stress to build up over time, which is eventually released in the form of seismic energy, resulting in earthquakes. These earthquakes can vary in intensity and frequency, depending on the nature of the fault and the movement of the plates.

In contrast, volcanic eruptions are more characteristic of divergent boundaries or convergent boundaries where subduction occurs. Mountain building, while it can happen at convergent boundaries where plates collide, is not typical at transform boundaries where the motion does not generally result in significant vertical uplift. Seafloor spreading occurs at divergent boundaries where new oceanic crust is formed, which is different from the lateral movement associated with transform faults. Thus, earthquakes are indeed the most likely condition to occur at transform fault boundaries.