Answer:
Continental ice sheets press down the Earth's crust.
Glaciers carve valleys out of the rock.
Explanation:
Glaciers and ice sheets are both bodies of ice and are part of the cryosphere. They interact with Earth's crust as they are forming over it. The interaction results in the creation of numerous different types of land-forms on the crust, as well as some processes that influence the elevation of the crust for example.
The continental ice sheets are enormous and they can be spread out over whole regions or when there is an ice age they can occupy big portions of the continents. They are also very thick, so their weight is enormous and they manage to actually push down the cru, thus the crust losses on elevation. Glaciers, on the other hand, are much smaller, and in many ways, they can be considered as very slow-moving rivers of ice. Because they move on top of the crust, the pressure they create manages to easily erode the rock surface, creating U-shaped valleys.
