Question
Physical weathering breaks intact rock into unconnected clasts (grains or chunks), collectively called debris or detritus. Each size range of clasts has a name. Many different phenomena contribute to physical weathering. State at least two phenomena and explain briefly
Answers
GPT-4o mini
Two phenomena that contribute to physical weathering are **freeze-thaw cycles** and **thermal expansion and contraction**.
1. **Freeze-Thaw Cycles**: This process occurs in climates where temperatures fluctuate around the freezing point. Water infiltrates cracks and pores in rocks, and when temperatures drop and the water freezes, it expands by about 9%. This expansion exerts pressure on the surrounding rock, causing it to fracture and break apart over time. When temperatures rise again and the ice thaws, the process can repeat, leading to further disintegration of the rock.
2. **Thermal Expansion and Contraction**: Rocks can be subjected to significant temperature variations, especially in desert environments. During the day, the sun heats the rock surface, causing it to expand. At night, cooler temperatures cause the rocks to contract. This repeated process creates stress within the rock material, leading to the development of micro-cracks. Over time, the accumulation of these stresses can result in the physical breakdown of the rock into smaller clasts.
Both of these processes illustrate how physical weathering can fragment rocks without the involvement of chemical changes.
1. **Freeze-Thaw Cycles**: This process occurs in climates where temperatures fluctuate around the freezing point. Water infiltrates cracks and pores in rocks, and when temperatures drop and the water freezes, it expands by about 9%. This expansion exerts pressure on the surrounding rock, causing it to fracture and break apart over time. When temperatures rise again and the ice thaws, the process can repeat, leading to further disintegration of the rock.
2. **Thermal Expansion and Contraction**: Rocks can be subjected to significant temperature variations, especially in desert environments. During the day, the sun heats the rock surface, causing it to expand. At night, cooler temperatures cause the rocks to contract. This repeated process creates stress within the rock material, leading to the development of micro-cracks. Over time, the accumulation of these stresses can result in the physical breakdown of the rock into smaller clasts.
Both of these processes illustrate how physical weathering can fragment rocks without the involvement of chemical changes.