Question 44

Oxygen reacts with iron in rocks to form rust.

This scenario illustrates chemical weathering as it involves a chemical reaction where oxygen interacts with iron in rocks, resulting in the formation of rust. This process alters the mineral composition of the rock, which is a key characteristic of chemical weathering.

A) Oxygen reacts with iron in rocks to form rust.

This option is correct because it specifically describes a chemical reaction that alters the mineral structure of rocks. The process of oxidation, where oxygen reacts with iron, leads to the creation of iron oxides or rust, demonstrating a fundamental aspect of chemical weathering.

B) Blown sand grinds down exposed rocks in a desert.

This option is incorrect as it describes mechanical weathering, not chemical weathering. The action of sand particles physically wearing away rock surfaces does not involve any chemical change to the minerals in the rocks.

C) Tree roots crack rocks as they grow into cracks.

This option is also incorrect because it illustrates physical or mechanical weathering. The physical force exerted by growing tree roots can break rocks apart, but it does not involve any chemical alteration of the rock's composition.

D) Cycles of hot and cold temperature form cracks in rocks.

This option is incorrect as it refers to physical weathering processes. The expansion and contraction of rocks due to temperature changes may cause cracking, but it does not change the chemical composition of the rocks involved.

Conclusion

The correct answer, which describes the reaction of oxygen with iron in rocks to form rust, is a clear example of chemical weathering. Other options fail to demonstrate chemical processes, instead focusing on physical changes that do not alter the internal structure of the rocks. Understanding these distinctions is crucial in identifying the types of weathering that shape our geological landscape.