Weathering. Weathering is the process by which natural forces break down rock.

Transcription

1 Weathering Weathering is the process by which natural forces break down rock.

2 Mechanical Weathering The breaking up of rocks by physical forces. Ice wedging Pressure release Plant root wedging Abrasion

3 Ice Wedging When water freezes in cracks of rocks the force of its expansion splits rocks apart.

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5 Pressure Release As pressure is released on a large area of rock, outer layers of the rock expand and break off.

6 Pressure Release

7 Plant Root Wedging Trees, bushes and other plants may take root in the cracks of rocks. As the roots grow, they apply enough pressure to split the rock.

8 Abrasion Wind, water, and ice carry rocks and sand that chip and grind the rocks they strike.

9 Examples of weathering by wind water and ice abrasion

10 Chemical Weathering The breakdown of rocks by chemical reactions that change the rocks makeup or composition.

11 Dissolving As water moves through the atmosphere carbon dioxide increases the waters acidity. This slightly acidic water can then fall as rain and dissolve rocks and minerals.

12 Stone statues dissolved by acid rain

13 Rusting Many rocks contain minerals with iron in them. When exposed to air and water these minerals change to rust.

14 Weathering Occurs at Different Rates Two different factors help determine how fast a rock will weather Surface area Rock composition

15 Surface area The more of a rocks surface that is exposed to air and water the faster it will weather.

16 Rock composition Rocks with greater strength or that are composed of minerals that do not easily dissolve, weather at a slower rate.

17 Soil Soil is a loose mixture of rock fragments, organic material, water, and air. Soil supports the growth of vegetation

18 Not All Soil Is the Same Scientist classify soil by its texture Soil texture is the quality of the soil that is based on the proportions of soil particles

19 There are three different sizes of soil particles. Sand 2mm-.05 mm Silt.05 mm-.002 mm Clay less than.002mm Soil Particles

20 Humus The dark, organic material formed in soil from the decayed remains of plants and animals.

21 Erosion and Deposition

22 Erosion Definition Erosion- The process in which weathered particles (sediment) are picked up and moved from one place to another.

23 Deposition Definition The process in which transported sediment is laid down.

24 Four Major Forces Of Erosion Gravity Water Wind Ice

25 Mass Wasting Mass wasting is the downhill movement of loose rock and soil. The force that causes mass wasting is gravity Mass wasting is usually triggered by water or earthquakes.

26 Types of Mass Wasting Rockslide Mudflow Slumps Creep

27 Rockslide A rockslide is a large mass of rock that slides down a slope as a unit. Rockslides can reach speeds up to 100 Km per hour.

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29 Mudflow A mudflow is the rapid movement of a large mass of mud. Mudslides are usually triggered by heavy rains.

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31 Slumps A slump is a slide of loose rock and soil that moves as a single unit. Moves at a much slower rate than rockslides or mudflows Usually triggered by heavy rain

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33 Creep Slowest form of mass wasting Rock and soil moves less than 1-10 mm per year.

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35 Water and Erosion Running water is the major force that shapes the land. Rain and melted ice and snow will either soak into the ground or flow on its surface

36 Stream Erosion Rivers and streams erode the rocks and soil they move across. The sediment that a stream carries is called the stream load. The steeper and faster moving the stream is, the faster it will erode.

37 Underground Water Water that soaks into the ground is called ground water. Ground water can be in the soil and in porous rock called an aquifer.

38 Ground Water Erosion and Weathering Ground water can chemically weather rock and remove the dissolved material causing caverns and sinkholes.

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40 Wind Erosion and Deposition Strong wind will pick up and move sand and dust particles. When the wind dies down it deposits the sand and dust.

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42 Erosion and Deposition by Ice Glaciers form where more snow falls than melts each year.

43 Glacial erosion Glaciers abrade rock and then transport the sediment as the glacier moves down hill.

44 Glacial deposits As glaciers retreat they leave behind sediment called till. Large deposits of till are called moraines.