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Weathering

Discover the importance of rocks, weathering, and soil formation in creating a sustainable environment. Learn about the different types of weathering, including mechanical and chemical, and how they shape the Earth's surface. Explore the role of water, wind, and other geological processes in weathering, and understand how climate, organisms, topography, parent materials, and time influence soil formation. Join us in the Library tomorrow for an informative session on this fascinating topic!

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Weathering

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  1. You need your spiral. We will be meeting in the Library tomorrow. Weathering

  2. Why do we care about rocks…? • We can always take pointers from earth on how to be sustainable. • Rocks make soil • Why is soil important? • Organisms, mainly microorganisms, inhabit the soil & depend on it for shelter, food & water. • Plants anchor themselves into the soil, and get their nutrients and water. Terrestrial plants could not survive without soil, therefore, humans could not exist without soil either.

  3. Soil Formation Parent Material • The rock that has slowly broken down into smaller particles by biological, chemical, and physical weathering. • To form 2.5 cm (1 in.) it may take from 200-1000 years.

  4. Mechanical Weathering: no change in chemical composition--just disintegration into smaller pieces

  5. Mechanical Weathering Exfoliation: Rock breaks apart in layers that are parallel to the earth's surface; as rock is uncovered, it expands (due to the lower confining pressure) resulting in exfoliation.

  6. Sheet Joints(Exfoliation)

  7. Half Dome, Yosemite, CA Stone Mountain, GA

  8. Exfoliated Domes, Yosemite

  9. Stone Mountain, Georgia, showing the product of exfoliation due to unloading Stone Mountain, GA

  10. Frost Wedging: rock breakdown caused by expansion of ice in cracks and joints

  11. Shattered rocks are common in cold and alpine environments where repeated freeze-thaw cycles gradually pry rocks apart.

  12. Thermal expansion due to the extreme range of temperatures can shatter rocks in desert environments. Repeated swelling and shrinking of minerals with different expansion rates will also shatter rocks. Weathering

  13. Agents Water Wind Geological processes

  14. Role of Physical Weathering • Reduces rock material to smaller fragments that are easier to transport 2) Increases the exposed surface area of rock, making it more vulnerable to further physical and chemical weathering

  15. Surface Area and Weathering

  16. Chemical Weathering • A plant’s roots or animal cells undergo cell respiration and the CO2 produced diffuses into soil, reacts with H2O & forms carbonic acid (H2CO3). This eats parts of the rock away. CHANGES THE COMPOSITION

  17. Olivine/pyroxene to clay + H2CO3 (acid)

  18. Feldspars to clay + H2CO3 (acid)

  19. Quartz to quartz (!) + anything

  20. This photo of Lime Sink was taken on 20 July 1932, over a week after the drawdown, which occurred over the night of 9-10 July. ‘Karst’ landforms develop in areas underlain with limestone

  21. Five main factors that affect the rate of weathering. Climate: Soil forms faster in warm, wet climates, because heat and moisture speed most physical, chemical and biological processes. Organisms: Plants and decomposers add organic matter to soil over time Topography: Hills and valleys affect exposure to sun, wind and water and they influence how soil moves (erosion) Parent materials: Its attributes influence properties of the resulting soil. Time: soil formation can take decades, centuries or millennia.

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