What happens when two tectonic plates slide past each other?

When two tectonic plates slide past each other, the primary geological phenomenon that occurs is the generation of earthquakes. This motion happens along faults, which are fractures in the Earth's crust where the plates interact. The friction between the sliding plates can cause stress to build up, and when this stress exceeds the frictional force, it is released in the form of seismic waves, resulting in an earthquake.

This process is characteristic of transform boundaries, where the lateral movement of the plates occurs. Although the sliding can lead to displacement and other geological impacts, the immediate and most significant effect is the seismic activity that can arise from the sudden release of energy as the plates move.

The other options mention processes associated with different plate interactions. For instance, mountains are typically formed at convergent boundaries where plates collide and mountain-building processes occur. Volcanic eruptions are primarily caused by subduction where one plate is forced below another, leading to the melting of mantle material. New oceanic crust is formed at divergent boundaries where plates are moving apart, allowing magma to rise and solidify. Thus, the action of sliding past each other is directly linked to the occurrence of earthquakes, making it the correct response to the question.