Here's why:

* Cirques: These are bowl-shaped depressions carved out by glacial erosion.

* Erosion: As glaciers erode a mountain, they carve out cirques on different sides.

* Convergence: When three or more cirques erode towards each other, they leave a sharp, pointed peak called a horn.

Some famous examples of horns include the Matterhorn in the Alps and the Grand Teton in Wyoming.