Here's why:

* Plate Tectonics: The Andes formed due to the convergent boundary between the Nazca Plate (oceanic) and the South American Plate (continental). The denser Nazca Plate subducts (slides) beneath the South American Plate.

* Folding: As the Nazca Plate descends, it drags the edge of the South American Plate downwards, causing the overlying rock layers to buckle, fold, and uplift. This process creates the towering peaks and valleys characteristic of folded mountain ranges.

Other types of mountains and their formation processes:

* Fault-block mountains: Formed by the movement of large blocks of rock along faults.

* Volcanic mountains: Formed by the accumulation of lava and ash from volcanic eruptions.

* Dome mountains: Formed by the uplift of a large area of rock.

* Plateau mountains: Formed by the erosion of a plateau.

The Andes are a prime example of how plate tectonics can shape the Earth's surface, creating majestic mountain ranges like the Andes.