2.3c weathering and erosion
- 1. 17.4 Weathering and Erosion To do: • Class reading: page 583 – 588. • Individual Silent Work: Vocabulary starting page 583
- 2. 17.4 Weathering and Erosion Weathering – The change in the physical form or chemical composition 0f rock materials exposed at Earth’s surface. Two types of the Weathering process: 1. Physical or mechanical – it is a kind of weathering that breaks rocks into smaller pieces but does not alter the rocks’ chemical composition.
- 3. 17.4 Weathering and Erosion Two types of the Weathering process: 1. Physical or mechanical – it is a kind of weathering that breaks rocks into smaller pieces but does not alter the rocks’ chemical composition. a. Ice (frost wedging) – occurs when water seeps into cracks or joints in rocks and then freezes. When water freezes, its volume increase by about 10% pushing the rock apart.
- 4. 17.4 Weathering and Erosion a. Ice (frost wedging) – occurs when water seeps into cracks or joints in rocks and then freezes. When water freezes, its volume increase by about 10% pushing the rock apart. b. Plants (plant wedging) – occurs when roots grow into cracks in the rocks. As the plant grows, the roots exert a constant pressure on the rock. The crack continues to deepen and widen, eventually causing a piece of the rock to break off.
- 5. 17.4 Weathering and Erosion b. Plants (plant wedging) – occurs when roots grow into cracks in the rocks. As the plant grows, the roots exert a constant pressure on the rock. The crack continues to deepen and widen, eventually causing a piece of the rock to break off. 2. Chemical Weathering- kind of weathering that breaks down rocks by changing its chemical composition.
- 6. 17.4 Weathering and Erosion 2. Chemical Weathering- kind of weathering that breaks down rocks by changing its chemical composition. a. Oxidation – When certain elements, specially metals, react with oxygen, they become oxides and their properties change.
- 7. 17.4 Weathering and Erosion a. Oxidation – When certain elements, specially metals, react with oxygen, they become oxides and their properties change. - Oxidation in minerals causes minerals to decompose or form new minerals causing both chemical and physical appearance of the rock to change. b. Carbon dioxide – carbon dioxide in the air dissolves in rainwater resulting to a carbonic acid.
- 8. 17.4 Weathering and Erosion b. Carbon dioxide – carbon dioxide in the air dissolves in rainwater resulting to a carbonic acid. - Although carbonic acid is a weak acid, it reacts with minerals, seeps into the ground and weather rocks underground. - Acid rain – slowly dissolves minerals caused burning fossil fuels in cars, power stations, factories
- 9. 17.4 Weathering and Erosion - Although carbonic acid is a weak acid, it reacts with minerals, seeps into the ground and weather rocks underground. - Acid rain – slowly dissolves minerals caused burning fossil fuels in cars, power stations, factories. - Acid rain damages both living organisms and non-living matter.
- 10. 17.4 Weathering and Erosion - Acid rain damages both living organisms and non-living matter. How does pollution contribute to acid rain? - Coal, oil and gasoline – release gases including sulfur dioxide reacting with water in the air and clouds to form nitric acid or nitrous acid and sulfuric acid.
- 11. 17.4 Weathering and Erosion How does pollution contribute to acid rain? - Coal, oil and gasoline – release gases including sulfur dioxide reacting with water in the air and clouds to form nitric acid or nitrous acid and sulfuric acid. - US Act of 1970 (Clean Air Act) – reduced the release of chemicals that cause acid rains. Acidity of rain is greatly reduced.
- 12. 17.4 Weathering and Erosion - US Act of 1970 (Clean Air Act) – reduced the release of chemicals that cause acid rains. Acidity of rain is greatly reduced. Erosion – removal and transportation of weathered and non-weathered materials by agents of erosion. Agents of Erosion: • running water • Wind
- 13. 17.4 Weathering and Erosion Erosion – removal and transportation of weathered and non-weathered materials by agents of erosion. Agents of Erosion: • running water • Wind • Waves • Ice • underground water • gravity.
- 14. 17.4 Weathering and Erosion • Ice • underground water • gravity. Notes on Erosion: • Water erosion shapes Earth’s surface • Water is by far the most effective physical weathering agent.
- 15. 17.4 Weathering and Erosion Notes on Erosion: • Water erosion shapes Earth’s surface • Water is by far the most effective physical weathering agent. • Rivers carry sediments that scrapes and scratch rocks and soil in riverbanks and river bottom • Deposition – the process of depositing sediments on the floor of calmer portions of rivers, lakes and sea.
- 16. 17.4 Weathering and Erosion Notes on Erosion: • Rivers carry sediments that scrapes and scratch rocks and soil in riverbanks and river bottom • Deposition – the process of depositing sediments on the floor of calmer portions of rivers, lakes and sea. • Glaciers erode mountains • Wind also shape landscapes
- 17. 17.4 Weathering and Erosion Poster: figure 17-35 on page 588