What must be present on a rock that undergoes frost wedging?
A. a crack
B. sharp edges
C. holes around it
D. round shape
A. a crack
A. a crack
To undergo frost wedging, a rock must have a crack present. During frost wedging, water enters the crack and expands when it freezes, exerting pressure on the rock and causing it to break apart.
To determine what must be present on a rock that undergoes frost wedging, we need to understand what frost wedging is. Frost wedging is a type of physical weathering that occurs when water freezes and expands within cracks or other openings in rocks. The expansion of the frozen water exerts pressure on the surrounding rock, causing it to crack or break apart.
Therefore, the correct answer is A. a crack. In order for frost wedging to occur, there must be pre-existing cracks or fractures in the rock where water can penetrate and freeze. The expansion of the freezing water will then wedge the rock apart, eventually leading to its breakdown.
The other options, B. sharp edges, C. holes around it, and D. round shape, are not necessarily related to frost wedging. They may be characteristic features of rocks but do not directly influence the occurrence of frost wedging.