Question

Soil formed by intensive leaching is _____.
A) Alluvial Soil
B) Red Soil
C) Laterite Soil
D) Desert Soil

Answer 1

Hint: This type of soil has high iron content. Its formation is due to the tropical weathering and the soil is also named after this phenomenon.

Complete answer:
The laterite soil is formed from the leaching of a parent sedimentary rock (sandstones, clay, limestones), metamorphic rocks, igneous rocks and mineralized proto-ores. In the mechanism of leaching, the host mineral lattice is dissolved by acidic actions, which is followed by the hydrolysis and precipitation of insoluble oxides and sulfates of iron, aluminum and silica under the high temperatures of sub-tropical monsoons.

The repetition of wet and dry climates is an important condition required for the formation of laterite soil. The process of tropical weathering that leads to the formation of this soil is also called lateralization. Since it is the tropical condition that enhances the formation of laterite soil, this type of soil is majorly found between the Tropic of Cancer and the Tropic of Capricorn.

The chemical composition of the soil is highly dependent on its parent rock, but it mainly consists of quartz, zircon, oxides of titanium, iron, tin, aluminum, and manganese. They have high clay content and hence a higher water holding capacity. Thus, laterite soil is good for cultivating oil palm, tea, coffee and cashew nuts.

Now let us analyze the given options:
Option (A) Alluvial soil - is formed by the deposition of silt by the rivers. This silt is in turn formed by the weathering of mountain rocks by the water current.
Option (B) Red soil - is formed by the weathering of crystalline and metamorphic rocks, and no leaching is involved in its formation. It is rich in potassium.
Option (D) Desert soil - is only formed in places where the rate of evaporation is five times the rate of precipitation in a year. It is formed from the windblown sediments (eolian) or from ancient rivers and lakes (which might not be present currently, but its deposits are).

Thus, the correct answer is Option (C) Laterite soil.


Note:
- Francis Buchanan Hamilton described and named the first laterite formation in Angadipuram, Kerala in 1807.
- To commemorate this event, a monument of laterite brickstones was set up at Angadipuram.
- In India, laterite soil covers around 10% of the total geographical area.