Here's why:

* Glaciers are powerful agents of erosion: They carve out valleys, grind down mountains, and transport massive amounts of rock and sediment.

* Moraines are the result of this transported material: As glaciers melt, the debris they carry is deposited, creating various types of moraines:

* Terminal moraine: Forms at the furthest point of glacial advance.

* Lateral moraine: Forms along the sides of a glacier.

* Medial moraine: Forms when two glaciers merge.

* Ground moraine: Forms beneath a glacier as it retreats.

So, while glaciers are powerful eroders, the moraines themselves are created by the accumulation and deposition of the eroded material.