Here's why:

* Erosion: Erosion is the process of wearing away and transporting material by natural forces like wind, water, and ice.

* Deposition: Deposition is the process of dropping or settling of sediments, rocks, and other materials that have been transported by natural forces.

How terminal moraines form:

1. Glacier movement: Glaciers, massive sheets of ice, move slowly over the land.

2. Plucking and abrasion: As the glacier moves, it erodes the underlying rock and soil through plucking (picking up rocks) and abrasion (grinding).

3. Transportation: These eroded materials are carried along within the glacier.

4. Deposition at the glacier's edge: When the glacier reaches its furthest point and begins to melt, it loses its ability to carry the sediment. This sediment is then deposited at the glacier's edge, forming a terminal moraine.

In summary: Terminal moraines are created by the deposition of material eroded by the glacier, not by the erosive forces of the glacier itself.