Weathering: Breakdown of Rocks into Soil

Weathering

• Weathering is the gradual breakdown of rocks in situ (stationary) to form soil.
• External forces such as rain, sunshine, wind, and temperature move and break down rocks.

Types of Weathering

• There are three types of weathering: physical/mechanical, chemical, and biotic.

Physical/Mechanical Weathering

• Physical weathering involves the disintegration or break down of rocks into smaller pieces.
• No chemical change occurs in the rock compound.
• Types of physical weathering include exfoliation and frost action.

Exfoliation

• Exfoliation occurs in arid regions such as deserts, where extreme daily temperature variations cause rocks to expand and contract.
• Continuous expansion and contraction of the rock lead to a significant breakdown in the rock's physical structure.
• The process of exfoliation results in the rock flaking off in layers, with small rock pieces broken off from the main rock known as scree.

Frost Action

• Frost action is caused by the alternate and repeated freezing and thawing of water in porous rocks, joints, cracks, and fissures.
• Water enters the rock, freezes, and expands by 10% in volume, exerting pressure and widening the fissure.
• Continuous freezing and thawing create stress on the rock structure, eventually breaking it down into smaller particles.
• Frost action mostly occurs in limestone rocks such as shale, sandstone, and limestone.

Chemical Weathering

• Chemical weathering occurs when rainwater filters down through rocks, destroying original minerals and forming new ones.
• The new material changes the mineral components, creating an adverse effect that breaks down the rock structure.
• Chemical weathering occurs in hot and humid regions, with types including carbonation and oxidation.