Which process initiates headwall erosion resulting to expansion of mountain cirques?

💡 Explanation

When snow accumulates in a mountain hollow, nivation weathering and freeze-thaw cycles occur because cycles weaken surface rocks via ice expansion, amplifying slope instability and subsequent mechanical removal which increases the steepness of the cirque headwall. Therefore headwall erosion results, rather than sediment flow, wind abrasion, or root wedging which require fundamentally different material characteristics and conditions.

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