Here's how it works:
* Glacial Erosion: Glaciers are powerful agents of erosion. As they move slowly downhill, they pick up rocks and debris, which act like sandpaper, grinding away at the underlying rock.
* Plucking: One important process is "plucking," where meltwater seeps into cracks in the rock, freezes, and expands, breaking off pieces of rock. This process is especially effective in areas where the rock is already fractured.
* Abrasion: The rocks and debris embedded in the ice also scrape and polish the bedrock, a process known as abrasion.
* Cirque Formation: Over time, this erosive action by the glacier carves out a bowl-shaped depression at the head of a valley, known as a cirque. The steep headwalls of a cirque are often formed by the plucking process, while the smooth, polished floor is a result of abrasion.
So, cirques are a direct result of glacial erosion.
