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Weathering and Soil Formation

Weathering and Soil Formation. The Effects of Weathering. Weathering is the process that breaks down rock and other substances at Earth's surface. What contributes to weathering? Heat Cold Water Ice all contribute to weathering. The Effects of Weathering.

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Weathering and Soil Formation

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  1. Weathering and Soil Formation

  2. The Effects of Weathering • Weathering is the process that breaks down rock and other substances at Earth's surface. • What contributes to weathering? • Heat • Cold • Water • Ice • all contribute to weathering.

  3. The Effects of Weathering • Forces of weathering break rock into smaller and smaller pieces. • Forces of erosion carry the pieces away. • Erosion is the movement of rock particles by wind, water, ice, or gravity • There are two kinds of weathering: • Mechanical weathering • Chemical weathering

  4. Mechanical Weathering • Weathering in which rock is physically broken into smaller pieces is called mechanical weathering. • smaller pieces have same composition as the original rock • Mechanical weathering breaks rock by • Freezing and thawing • Release of pressure • Growth of plants • Actions of animals • Abrasion • Abrasion refers to the grinding away of rock, by rock particles carried by water, ice, wind, or gravity.

  5. Mechanical Weathering

  6. Chemical Weathering • Chemical weathering is the process that breaks down rock through chemical changes. • The agents of chemical weathering include • Water • Oxygen • Carbon dioxide • Living organisms • Acid rain • Chemical weathering produces rock particles that have a different mineral makeup from the rock they came from.

  7. Chemical Weathering

  8. Chemical and Mechanical Weathering • Chemical and mechanical weathering often work together. • As mechanical weathering breaks rock into pieces, more surface area becomes exposed to chemical weathering.

  9. Water • How does water contribute to weathering? • Water is the most important agent of chemical weathering. • Water weathers rock by dissolving it. • When a rock or other substance dissolves in water, it mixes throughout the water to make a solution. • Over time, many rocks will dissolve in water. • Water can also freeze, expand in rock and break it apart. (Ice wedging)

  10. Oxygen • How does oxygen contribute to weathering? • The oxygen gas in air is an important cause of chemical weathering. • Bicycle or metal tool outside in the rain • Iron combines with oxygen in the presence of water in a process called oxidation. • The product of oxidation is rust. • Rust makes rock soft and crumbly

  11. Living Organisms   • How do living organisms contribute to weathering? • Weak acids that slowly dissolve rock around the roots. • Plantlike organisms that grow on rocks—also produce weak acids that chemically weather rock.

  12. Acid Rain   • How does acid rain contribute to weathering? • Over the past 150 years, people have been burning large amounts of coal, oil, and gas for energy. • Burning these fuels can pollute the air with sulfur, carbon, and nitrogen compounds. • Such compounds react chemically with the water vapor in clouds, forming acids. • These acids mix with raindrops and fall as acid rain. • Acid rain causes very rapid chemical weathering

  13. Rate of Weathering • The most important factors that determine the rate at which weathering occurs • Type of rock • Climate

  14. Permeable Rocks • Some rock weathers easily because it is permeable. • Permeable means that a material is full of tiny, connected air spaces that allow water to seep through it. • Permeable rock weathers chemically at a fast rate

  15. Climate • How does climate contribute to weathering? • Climate refers to the average weather conditions in an area. • Both chemical and mechanical weathering occur faster in wet climates. • Chemical reactions occur faster at higher temperatures.

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