Here's why:

* Frozen Water: Glaciers are massive bodies of ice formed from compacted snow.

* Move Rocks and Boulders: Glaciers slowly flow downhill, carrying rocks and boulders embedded within them. This process is called glacial erosion.

* Great Changes on Earth: Glaciers carve out valleys, create U-shaped valleys, deposit sediment to form moraines, and contribute to the formation of lakes and other landforms. These changes are significant and can be seen across the Earth.

Let me know if you'd like to know more about glaciers!