What must be present on a rock that undergoes frost wedging?
A rock that undergoes frost wedging must have certain characteristics or properties. These include:
1. Porosity: The rock must have open spaces or cracks that can be filled with water.
2. Permeability: The rock must have the ability to allow water to enter its pores or cracks.
3. Freeze-thaw susceptibility: The rock must be susceptible to freezing and subsequent expansion of water when it freezes.
These properties allow for the occurrence of frost wedging, a process that occurs mainly in colder climates and involves the following steps:
1. Water enters the pores or cracks of the rock.
2. The temperature drops below freezing, causing the water to freeze and expand.
3. As water freezes and expands, the pressure exerted by the ice pushes against the sides of the rock, exerting force and eventually causing cracks or fractures.
4. When the ice melts, the water seeps deeper into the cracks, and the cycle repeats, widening and deepening the cracks over time.
Therefore, for frost wedging to occur, a rock must have porosity, permeability, and freeze-thaw susceptibility to allow the entry and expansion of water through its cracks and pores.