Weathering

Chapter 6, Section 1

Weathering and Its Effects

Weathering Surface processes that break down rock. Rock breaks down into sediment. Sediment breaks down into soil.

2 Types Mechanical Weathering Chemical Weathering

Mechanical Weathering

Mechanical Weathering

Occurs when rocks are broken apart by physical processes.

Mechanical weathering increases the exposed surface area of the rock.

Mechanical Weathering

Examples of mechanical weathering:

1. Plants

2. Burrowing animals

3. Ice Wedging1. Water enter cracks in rock.

2. Water freezes and expands.

3. Force of expansion breaks the rock apart.

Chemical Weathering

Chemical Weathering

Occurs when chemical reactions dissolve or change the minerals in the rock.

May weaken the rock.

Chemical Weathering

Examples of Chemical Weathering

1. Natural Acids1. Water mixes with carbon dioxide

in the air or soil to form carbonic acid.

2. Carbonic acid reacts with calcite and dissolves limestone.

3. Over time, caves are formed.

Chemical Weathering

Examples of Chemical Weathering:

2. Natural Acids Over time acids can react with

feldspar (found in granite and sandstone) to form the clay kaolinite.

Chemical Weathering

Examples of Chemical Weathering:

3. Plant Acids Acids in roots or acids formed by

decaying plants can dissolve the mineral in the rock.

Chemical Weathering

Examples of Chemical Weathering

4. Oxidation Exposure of metallic minerals to

air and water causes them to “rust”. Ex: Magnetite into limonite.

Effects of Climate

Mechanical weathering

Chemical weathering

Increases in areas with frequent freezing and thawing.

Is most rapid in warm, humid areas.

Effects of Weathering

Effect of Rock Type:

Marble weathers more rapidly than granite in humid climates.