Weathering Charity I. Mulig. Weathering is the … physical breakdown (disintegration) and chemical...
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Transcript of Weathering Charity I. Mulig. Weathering is the … physical breakdown (disintegration) and chemical...
![Page 1: Weathering Charity I. Mulig. Weathering is the … physical breakdown (disintegration) and chemical alteration (decomposition) of rocks at or near the Earth’s.](https://reader035.fdocuments.us/reader035/viewer/2022062308/56649eaa5503460f94baeff2/html5/thumbnails/1.jpg)
Weathering
Charity I. Mulig
![Page 2: Weathering Charity I. Mulig. Weathering is the … physical breakdown (disintegration) and chemical alteration (decomposition) of rocks at or near the Earth’s.](https://reader035.fdocuments.us/reader035/viewer/2022062308/56649eaa5503460f94baeff2/html5/thumbnails/2.jpg)
Weathering is the …
physical breakdown (disintegration) and chemical alteration (decomposition) of rocks at or near the Earth’s surface.
![Page 3: Weathering Charity I. Mulig. Weathering is the … physical breakdown (disintegration) and chemical alteration (decomposition) of rocks at or near the Earth’s.](https://reader035.fdocuments.us/reader035/viewer/2022062308/56649eaa5503460f94baeff2/html5/thumbnails/3.jpg)
Types of Weathering
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Mechanical Weathering
Accomplished by physical forces that break rock into smaller pieces without changing its mineral composition
![Page 5: Weathering Charity I. Mulig. Weathering is the … physical breakdown (disintegration) and chemical alteration (decomposition) of rocks at or near the Earth’s.](https://reader035.fdocuments.us/reader035/viewer/2022062308/56649eaa5503460f94baeff2/html5/thumbnails/5.jpg)
Examples of Mechanical Weathering
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Frost Wedging
• Caused by repeated freesing and thawing of water
Talus Slopes- Result of frost wedging.- Accumulated rocks
usually piles at the base of steep rocky cliffs
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Unloading
• Reduced pressure on igneous rock causes it to expand and allows slabs of outer rock to break off in layers in a process called exfoliation.
Sheeting is the process of exfoliation.
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Biological Activity
• organisms, including plants, burrowing animals, and humans, can cause mechanical weathering
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Examples of Chemical Weathering
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Chemical Weathering
• The original rock decomposes into substances (mineral/compounds) that are stable in the surface environment.
• Products of chemical weathering will remain essentially unchanged as long as they remain in an environment similar to the one in which they formed.
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Chemical Weathering
• “water is the most important agent of chemical weathering”
• Water tend to:– Dissolve oxygen which then oxidizes minerals– Combine with carbon dioxide and form carbonic
acid which acts on rocks
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Chemical Weathering…of Granite …of Silicate
• produces clay minerals, soluble salt (potassium bicarbonate), and silica in solution
•quartz remains substantially unaltered
• produces insoluble iron oxides and clay minerals
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Chemical Weathering
• Spheroidal Weathering– Process which leads to
rocks taking a more rounded shape
– May lead to spalling
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Factors Affecting Rates of Weathering
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Mechanical Weathering
Increases the surface area available for chemical attack
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Rock Characteristics
• Encompasses all the chemical traits of rocks including mineral composition, solubility and physical features such as joints or cracks.
– Silicates are relatively more resistant to chemical weathering than calcites
– Silicates weather in the same sequence as their order of crystallization.
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Climate
• Temperature and moisture are the most crucial factors.
• Chemical weathering is most effective in areas with high temperatures and abundant moisture.
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Rate of Weathering
• Differential Weathering–Masses of rock do not weather
uniformly–Caused by variations in composition–May create spectacular rock
formations and landforms
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Other Links
• http://geology.about.com/od/geoprocesses/ig/chemweathering/basaltrind.htm