SS3 Second Term Geography Lesson Note – Weathering II

The content is just an excerpt from the complete note for SS3 Second Term Geography Lesson Note – Weathering II. Check below to download the complete DOCUMENT

WEEK 2   

TOPIC: WEATHERING

CONTENT:

1. CHEMICAL WEATHERING
2. Solution
3. Oxidation
4. Hydration
5. Carbonation
6. BIOLOGICAL WEATHERING

Plants, animals, burrowing and human activities

SUB-TOPIC 1: CHEMICAL WEATHERING

Chemical weathering is the gradual disintegration of rocks due to their exposure air and water. The processes are enhanced by high temperature and abundance of water supply, and are most intense at the base of steep slope where there is high moisture status due to fluctuating water table. It is common in hot-wet climate or humid regions with high temperature.

The major processes involved in chemical weathering include:

1. SOLUTION: Rain water attacks and dissolves rock salt to form solution. For instance, rain water dissolves calcium carbonate (CaCo₂) of limestone, thereby widening cracks and joints in the rocks.
2. OXIDATION: This process is the reaction of oxygen in air or water with minerals in rock. Most rocks contain a certain amount of iron in reduced form. The reduced iron is oxidized when it comes in contact with oxygen. The oxidized iron is stable because it is only soluble under extreme acid conditions. The stable iron oxidizes are readily precipitated. This causes the loosening of the overall structure of the rocks and accounts for the accumulation of oxidized iron and the formation of laterite in the tropics.
3. HYDRATION: This is the process whereby certain minerals within rocks absorbs water and are chemically altered. This process leads to the formation of hydroxides. The action weakens the rocks which may eventually disintegrate.
4. CARBONATION: This process of chemical weathering is often called carbon dioxide in the air and turns into a weak acid called carbonic acid. As water from rain enters into the ground, the acid reacts with the rocks that are rich in calcium carbonate like limestone and alters the calcium carbonate to calcium bicarbonate. The weak acid water dissolves and removes the calcium bicarbonate. This carbonation is most active in the decomposition of calcareous rocks, especially limestone and dolomite.
5. HYDROLISIS: This is the chemical reaction between rock minerals and water, usually with hydrogen as catalyst. It occurs frequently in the weathering of feldspars and micas whereby clay minerals are formed.

To gain full access to the note: DOWNLOAD FILE