Which process generates a tarn when glacial ice melts within a cirque basin?

💡 Explanation

When glacial ice melts, an impermeable bedrock layer beneath the cirque basin prevents drainage because it restricts water percolation, promoting water pooling. Therefore, a tarn (small lake) forms, rather than increased depth from isostatic rebound, sediment accumulation, or enhanced erosion by chemical weathering which require alternative mechanisms and conditions.

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