The process of frost wedging can be best described as the expansion of water in cracks and crevices due to freezing and causing the rock to fragment.
The phrase "a physical weathering process caused by the expansion of water upon freezing" best describes frost wedging.
Frost wedging is a geological process in which water freezes and expands in cracks and crevices of rocks, exerting pressure that causes the rocks to fragment and break apart. This phrase best describes frost wedging: "The mechanical weathering of rocks due to the expansion of water upon freezing."
