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Weathering This week we write it down if its in ORANGE. Photo: Grand Canyon, National Park Service.

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Presentation on theme: "Weathering This week we write it down if its in ORANGE. Photo: Grand Canyon, National Park Service."— Presentation transcript:

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2 Weathering This week we write it down if its in ORANGE. Photo: Grand Canyon, National Park Service

3 What do you think made the hole in this rock? Wind blows sand and other sediment against rocks. Little by little, it wears away the rock! This is an example of mechanical weathering.

4 What do you think made the notch where the waterfall starts? Water from the river wears away the rock, over thousands of years. This is another example of weathering. Photo: Yosemite Falls, National Park Service webcam

5 Weathering is the process that breaks down rock and other substances on Earths surface.

6 Part 1: Mechanical Weathering

7 Mechanical Weathering Force of Mechanical Weathering How it Works Abrasion Plant Growth Animal Actions Freezing and Thawing Release of Pressure

8 Abrasion: Sand and other rock particles carried by wind and water grind away rock like sandpaper on wood. Here we go again with wind and rock particles sculpting rock! Photo: Delicate Arch, Arches National Park, National Park Service.

9 Plant Growth: Roots of trees and other plants grow in the cracks of rocks and pry them apart. Perhaps you have seen this on sidewalks? Photo source: Morguefile.com

10 Animal Actions: Animals dig in the soil and loosen and break apart rocks. Photo source: Morguefile.com

11 Ice Wedging: When water freezes it expands. Ice in the crack of a rock expands and makes the crack larger. Perhaps you have seen a frozen bottle get cracked? Or cracks in the road? Why does that happen?

12 Whiteboard Question CHECK YOUR UNDERSTANDING! Mechanical weathering in which rock is worn away by the grinding action of other rock particles is called A. erosion. B. abrasion. C. ice wedging. B. abrasion

13 Release of Pressure: When rocks reach Earths surface, reduced pressure can cause cracks and flakes in the rock.

14 Mechanical Weathering Force of Mechanical Weathering How it Works AbrasionSand and other rock particles carried by wind and water grind away rock like sandpaper on wood. Plant GrowthRoots of trees and other plants grow in the cracks of rocks and pry them apart. Animal ActionsAnimals dig in the soil and loosen and break apart rocks. Freezing and Thawing When water freezes it expands. Ice in the crack of a rock expands and makes the crack larger. Release of PressureWhen rocks reach Earths surface, reduced pressure can cause cracks and flakes in the rock. Your completed chart should look like this!

15 Whiteboard Question CHECK YOUR UNDERSTANDING! Ice wedging causes mechanical weathering of rock by means of: A. plant growth. B. animal actions. C. freezing and thawing of water. C. freezing and thawing of water

16 Chemical Weathering Write it down if its in ORANGE.

17 Chemical weathering is the process that slowly breaks down rock with chemical changes, including changes in the minerals. This rusty color is caused by oxidation in a wet climate.

18 Whiteboard Question CHECK YOUR UNDERSTANDING! What kind of weathering causes the mineral composition of rocks to change? A. Chemical weathering. B. Mechanical weathering. C. General weathering. A. Chemical weathering

19 Part 2: Chemical Weathering

20 Chemical Weathering Chemical weathering is____________________________________________ _______________________________________________________________ Force of Chemical Weathering How it Works Water Oxygen Carbon Dioxide Living Organisms Acid Rain

21 Water: Water is the most important cause of chemical weathering. When a rock dissolves in water, it mixes completely with the water. This limestone cave was created by water dissolving the stone. Photo source: Morguefile.com

22 What made this old truck rusty? Photo source: Morguefile.com

23 Oxygen: Iron combines with oxygen and water in a process called oxidation. The result is rust. Oxidation of a rock makes it soft, crumbly and red or brown. Rust happens to old vehicles, and to rocks. Photo source: Morguefile.com

24 Carbon dioxide: Carbon dioxide in the air dissolves in rainwater, becoming a weak acid called carbolic acid. Acids weather rocks such as limestone and marble. Limestone.

25 Living organisms: Plants, and other living organisms such as lichen, release weak acids that slowly dissolve rocks. Lichen growing on a rock will weather it. Photo source: Morguefile.com

26 Acid rain: Burning coal, oil, and gas for energy produces pollution. This pollution combines with air and water, to create acid rain, and fast chemical weathering. Photo source: Morguefile.com

27 Whiteboard Question CHECK YOUR UNDERSTANDING! A rock containing iron becomes soft and crumbly and reddish-brown in color. It probably has been weathered by: A. abrasion B. oxygen. C. acid rain. B. oxygen

28 Chemical Weathering Chemical weathering is____________________________________________ _______________________________________________________________ Force of Chemical Weathering How it Works Water Water is the most important cause of chemical weathering. When a rock dissolves in water, it mixes completely with the water. Oxygen A rock containing iron becomes soft and crumbly and reddish-brown in color. It probably has been weathered by Carbon Dioxide Carbon dioxide in the air dissolves in rainwater, becoming a weak acid called carbolic acid. Acids weather rocks such as limestone and marble. Living Organisms Plants, and other living organisms such as lichen, release weak acids that slowly dissolve rocks. Acid Rain Burning coal, oil, and gas for energy produces pollution. This pollution combines with air and water, to create acid rain, and fast chemical weathering. Your completed chart should look like this!

29 Is it Chemical or Mechanical Weathering? Final Whiteboard Questions Abrasion of a rock by blowing sand is an example of __________________ weathering. Acid rain washing away the face of a statue is an example of __________________ weathering. True or False? Living things can cause both chemical and mechanical weathering. A trees roots growing through cracks in a rock is an example of _________________ weathering. mechanical True chemical mechanical

30 Part 3: Rates of Weathering What makes a rock weather fastest? Photo source: Morguefile.com

31 The most important factors for the rate (speed) of weathering are 1. rock type; and 2. climate. Rate of Weathering Photo source: Morguefile.com

32 Mechanical and Chemical Weathering Work Together Mechanical weathering increases the surface area available for chemical weathering. Increased surface area usually results in faster chemical reactions (chemical weathering). Photo source: Morguefile.com

33 Mechanical and Chemical Weathering Work Together A permeable rock weathers easily because it contains many small, connected air spaces Which rock do you think will weather faster?

34 Whiteboard Question CHECK YOUR UNDERSTANDING! A permeable rock weathers easily because it: A. is made up of small particles. B. contains many small, connected air spaces. C. is made up of many minerals. B. contains many small, connected air spaces.

35 Which of these places would have faster weathering of rock? Why? How Does Weather Affect Weathering? Photo source: Morguefile.com

36 Rainforests have warm, wet weather. Wet climates with high temperatures speed up both mechanical and chemical weathering. Photo source: Morguefile.com

37 Whiteboard Question CHECK YOUR UNDERSTANDING! Granite lasts a long time when it is used for building in areas where the climate: A. is cool. B. has lots of acid rain. C. is hot and rainy. A. is cool

38 Whiteboard Question CHECK YOUR UNDERSTANDING! The most important factors in determining the rate of weathering are: A. carbon dioxide and acid rain. B. animal actions and oxygen. C. rock type and climate. D. abrasion and acids from root plants. C. rock type and climate


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