What geological phenomenon is primarily associated with transform boundaries?

Transform boundaries occur where two tectonic plates slide past each other horizontally. This lateral movement can cause significant stress to build up along the faults, leading to sudden releases of energy that manifest as earthquakes. The earthquakes associated with transform boundaries can vary in intensity but are generally frequent due to the continuous movement of the plates.

In contrast, the formation of new mountains and ocean ridges is more closely associated with convergent and divergent boundaries, respectively. Similarly, rift valleys form where tectonic plates are moving apart, which is characteristic of divergent boundaries. Therefore, the primary geological phenomenon linked to transform boundaries is indeed the occurrence of frequent earthquakes, making this answer the most accurate.