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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.
Coastal notch
Coastal notches are erosional features characterized by subhorizontal indentations formed at the base of resistant coastal cliffs. Their height and depth can range from a few centimeters to several meters, depending on tidal range, wave energy, rock strength, and other factors. Because they develop through processes such as abrasion, weathering, dissolution, and bioerosion occurring near the high tidal level, they are considered reliable indicators of past sea levels when observed along submerged…