Before revision: Though often hemmed-in by sheer cliff walls, couloirs may also be less well-defined, often simply being a line of broken talus or scree ascending the mountainside and bordered by trees or other natural features.
After revision: Though often hemmed in by sheer cliff walls, couloirs may also be less well-defined, and often simply a line of broken talus or scree ascending the mountainside and bordered by trees or other natural features.