Weathering Weathering n Weathering is the process that

Weathering

Weathering n Weathering is the process that breaks down rock and other substances at the Earth’s surface. n There are 2 types of weathering: mechanical and chemical.

Mechanical Weathering n n Mechanical weathering is where rock is physically broken down into smaller pieces. There are 5 agents for this type of weathering: n n n Abrasion Freezing & thawing Heating & cooling Plant growth Animal activity

1. Abrasion is the grinding away of rock by rock particles carried by water, ice, wind or gravity. 2. Freezing & thawing-as water freezes and thaws in cracks of rocks, it causes the cracks to widen and deepen (ice wedging). 3. Heating & cooling-sun, forest fire and rain can heat and cool a rock causing it to break. 4. Plant growth- roots of plants enter cracks in rocks, as roots grow, they force the cracks farther apart. 5. Animal activity-animals that burrow loosen and break apart rocks and soil.

Chemical Weathering n n Chemical weathering is when rock is broken down through chemical changes. There are 5 agents for chemical weathering: n n n Water Oxygen Carbon dioxide Living organisms Acid rain

1. Water- dissolves rock 2. Oxygen- causes rocks that contain iron to rust (oxidation). 3. Carbon Dioxide- forms carbonic acid with rain that weathers marble and limestone. 4. Living Organisms- plant roots and lichens produce weak acids that weather rock. 5. Acid rain- pollutants in the air react with water vapor.

The rate of weathering is how fast weathering takes place. It is determined by the type of rock and climate. n n A stable rock is one that has minerals that are resistant to chemical weathering. The more moisture there is in an area, the more quickly the rock will weather.

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