Glacial polish is a characteristic of rock surfaces where glaciers have passed over bedrock, typically granite or other hard igneous or metamorphic rock. Moving ice will carry pebbles and sand grains removed from upper levels which in turn grind a smooth or grooved surface upon the underlying rock.^[1] The presence of such polish indicates that the glaciation was relatively recent (in geologic time scale) or was subsequently protected by deposition, as such polish will be subsequently lost due to weathering processes (such as exfoliation).

Considering some samples of glacial polish from sites such as Yosemite National Park, scientists have discovered that they developed thin coatings composed of tiny rock particles rather than rocks just being worn down solely from the movement of the glaciers.^[2] Over time, this coating contributes to the smoothness of the rocks. This coating also helps protect the polished rocks from natural processes such as weathering and erosion. This discovery has altered how scientists consider glaciers’ effect on land.

• Glacial striation
• Sierra Nevada