Question 50

The cracking of a rock caused by the freezing and thawing of water is an example of physical weathering.

Physical weathering occurs when rocks break apart without changing their chemical structure. The process described in option A illustrates this concept as the repeated freezing and thawing causes physical stress on the rock, leading to its cracking.

A) The cracking of a rock caused by the freezing and thawing of water.

This option accurately exemplifies physical weathering, as it involves the mechanical breakdown of rock due to temperature fluctuations. The water seeps into cracks, freezes, expands, and then thaws, repeatedly stressing the rock until it fractures.

B) Sediments being transported in a stream.

While sediment transport is a significant geological process, it does not exemplify physical weathering. Instead, this option describes erosion, where already weathered materials are moved from one location to another, rather than the breakdown of rock itself.

C) A sandbar forming in a stream.

The formation of a sandbar is a result of sediment deposition and does not represent physical weathering. This process involves the accumulation of sediments transported by water, rather than the mechanical breakdown of solid rock.

D) Acid rain dissolving a statue.

This option refers to chemical weathering, not physical weathering. Acid rain chemically alters the minerals in the statue, leading to dissolution and changes in the rock's chemical structure, which is distinctly different from the mechanical processes involved in physical weathering.

Conclusion

The correct answer, option A, clearly defines an example of physical weathering as it involves the mechanical breakdown of rock due to freeze-thaw cycles. In contrast, options B, C, and D focus on processes related to erosion and chemical weathering, which do not fit the criteria for physical weathering. Thus, option A stands out as the only correct example in the context provided.