(a) What is weathering ? (b) Enumerate three processes involved in rock weathering (c) List and discuss briefly the agents of two of these processes

(a) Weathering is the process by which rocks and minerals are broken down into smaller pieces or dissolved by physical, chemical or biological processes, in response to the conditions of the environment in which they exist.

(b) The three processes involved in rock weathering are:

1. Mechanical or physical weathering: This process involves the physical breakdown of rocks into smaller pieces without changing their chemical composition. Examples of mechanical weathering include freeze-thaw cycles, root wedging, abrasion, and exfoliation.
2. Chemical weathering: This process involves the chemical breakdown of rocks and minerals by the action of water, air, and other chemicals. Examples of chemical weathering include oxidation, hydrolysis, carbonation, and acid rain.
3. Biological weathering: This process involves the breakdown of rocks and minerals by the action of living organisms such as plants, animals, and microorganisms. Examples of biological weathering include root penetration, burrowing by animals, and decay by microorganisms.

(c) The agents of mechanical weathering are physical forces such as temperature changes, wind, water, and ice. For example, freeze-thaw cycles occur when water freezes in rock crevices and then expands as it turns into ice, causing the rock to crack and break apart.

The agents of chemical weathering are chemical compounds such as water, oxygen, carbon dioxide, and acids. For example, carbon dioxide in the air combines with water to form carbonic acid, which can dissolve minerals in rocks such as limestone, leading to their erosion and breakdown over time. Another example is acid rain, which results from the combination of rainwater with pollutants such as sulfur dioxide and nitrogen oxides, leading to the corrosion and breakdown of rocks and other structures.