Striations

In glacial environments, rocks transported by ice can be grinded by friction with bedrock or other rocks. This physical abrasion can leave distinctive marks such as "facets" (flat, polished surfaces on clasts) and "striations" (linear grooves, typically parallel to the direction of ice flow). This faceted and striated boulder was photographed at Rocky Mountain National Park (CO), within glacial moraine deposits. Dashed line added to indicate main orientation of striations. Scale in 10 cm increments.

glaciation striations abrasion boulder