* Mountains:

* Convergent Boundaries: These are where plates collide. The immense pressure and force of the collision can cause one plate to buckle and fold, creating mountain ranges. The Himalayas, the Andes, and the Alps are all examples of mountain ranges formed at convergent boundaries.

* Transform Boundaries: While not as common as at convergent boundaries, mountains can also form at transform boundaries where plates slide past each other. The friction and stress along these boundaries can cause uplift and create mountain ranges. The San Andreas Fault in California is a good example.

* Volcanoes:

* Convergent Boundaries: Subduction zones (where one plate dives under another) are especially prone to volcanic activity. As the descending plate melts, magma rises to the surface, creating volcanoes. The Ring of Fire, a zone of intense volcanic activity around the Pacific Ocean, is a prime example.

* Divergent Boundaries: These are where plates pull apart. Magma rises to the surface to fill the gap, forming new crust and volcanoes. The Mid-Atlantic Ridge is a great example of a divergent boundary with underwater volcanoes.

In summary: Plate boundaries are zones of immense geological activity, and the forces involved lead to the formation of both mountains and volcanoes.