1. Weathering & Erosion
Choose OK

2. What is weathering?
Weathering is a set of physical, chemical and biological processes that change the physical and chemical properties of rocks and soil at or near the earth's surface.

3. More about weathering
Definition – the breakdown of rock to form sediment [very small pieces of rock]
Weathering happens to rocks that are NOT MOVING
Weathering is part of the Rock Cycle

4. There are three types of weathering
Mechanical [sometimes called physical]
Chemical
Biological

5. Mechanical weathering breaks rocks down into smaller pieces.
Types of mechanical weathering include frost wedging, exfoliation, and thermal expansion.

6. Chemical weathering breaks rocks down chemically adding or removing chemical elements, and changes them into other materials.
Chemical weathering consists of chemical reactions, most of which involve water.

7. Biological weathering is the breakdown of rock caused by the action of living organisms, including plants, burrowing animals, and lichens.
A lichen is a combination of fungus and algae, living together in a symbiotic relationship.
Lichens can live on bare rock, and they break down rocks by secreting acids and other chemicals.

8. Let’s investigate mechanical weathering first.

9. In mechanical weathering, a rock is broken down into smaller pieces without changing its mineral composition.

10. There are several different processes that cause mechanical weathering.
View Website

11. Observe the effects of mechanical weathering
View Website
View Website 2
Website 3

12. Enchanted rock is a huge example of exfoliation mechanical weathering.

13. Discuss with your partner how exfoliation, abrasion and thermal expansion are examples of mechanical weathering

14. Now, let’s look at chemical weathering.

15. In chemical weathering, a rock is broken down by chemical reactions that change its mineral composition and physical and chemical properties

16. Chemical weathering happens when the minerals that make up a rock are changed, leading to the disintegration of the rock

17. The warm weather speeds up the reactions.
Chemical weathering happens quickly in warm, moist environments because water is needed for the chemical reactions.
The warm weather speeds up the reactions.

18. Not all minerals are prone to chemical weathering
Not all minerals are prone to chemical weathering. For example, feldspar and quartz, are common minerals in the rock granite, have very different levels of resistance to chemical weathering.
Quartz doesn’t weather very easily, but feldspar does. Over a long time, it chemically changes into clay minerals.

19. View the following websites to learn more about chemical weathering
1.) Feldspar to clay
2.) Examples of more chemical weathering

20. Biological weathering involves processes that can be either chemical or physical in nature. Biological weathering can be considered special types of mechanical or chemical weathering.

21. Biological weathering – What is it?

22. Some biological weathering processes are:
1. Rocks can break because of animal burrowing.
2. Tree roots grow into cracks and widen them, which helps physical weathering.
3. Bacteria, lichens and other organisms secrete acidic solutions, which helps chemical weathering.

23. Lichens on rocks cause biological weathering by secreting an acid that breaks down the rock.

24. Plants growing in rocks break the rocks apart.

25. Now let’s move on to EROSION

26. What is erosion?
Erosion is defined as the removal and movement of earth materials by natural agents.
Some of these agents include glaciers, wind, water, earthquakes, volcanoes, tornadoes, hurricanes, mud flows, and avalanches.

27. How are erosion & weathering different?
Weathering involves two processes
[mechanical, chemical]
that often work together to break down rocks. Both processes occur in place. No movement is involved in weathering.

28. Mass wasting is simply movement down slope due to gravity.
As soon as a rock particle (loosened by one of the two weathering processes) moves, we call it erosion or mass wasting.
Mass wasting is simply movement down slope due to gravity.
Rock falls, slumps, and debris flows are all examples of mass wasting. We call it erosion if the rock particle is moved by some flowing agent such as air, water or ice.

29. put, we call it weathering.
In a nutshell: if a particle is loosened, chemically or mechanically, but stays
put, we call it weathering.
Once the particle starts moving, we call it erosion.

30. What are the different types of erosion? View the website to find out.

31. Water is the most important erosional agent and erodes most often as running water in streams or rivers.

32. Water in all its forms is erosional
Water in all its forms is erosional. Raindrops create splash erosion that moves tiny particles of soil. Water collecting on the surface of the soil collects as it moves towards tiny streams and creates sheet erosion.

33. Observe river erosion causing waterfalls Visit this website

34. Erosion by wind is known as aeolian erosion (named after Aeolus, the Greek god of winds) and usually occurs in deserts. Aeolian erosion of sand in the desert is partially responsible for the formation of sand dunes.

35. Painted Desert National Monument

36. The erosive power of moving ice is actually a greater than the power of water. however since water is much more common, it is responsible for a greater amount of erosion on the earth's surface.

37. Glaciers cause erosion two ways - they pluck and abrade
Glaciers cause erosion two ways - they pluck and abrade. Plucking takes place by water entering cracks under the glacier, freezing, and breaking off pieces of rock that are then moved by the glacier. Abrasion cuts into the rock under the glacier, scooping rock up like a bulldozer and smoothing and polishing the rock surface.

38. Athabasca Glacier - Jasper, Canada

39. Waves in oceans and other large bodies of water cause coastal erosion.
The power of ocean waves is awesome; large storm waves can produce 2000 pounds of pressure per square foot. The pure energy of waves along with the chemical content of the water is what erodes the rock of the coastline.

40. Wave action in Calvert County Maryland

41. Watch wave erosion on this website

42. Observe landscapes formed by erosion click on the website

43. Let’s look at some more examples of erosion.
Website

44. Explore the formation of the Grand Canyon

45. Review weathering & erosion vocabulary with online flashcards
Review weathering & erosion vocabulary with online flashcards. Note: Some of the terms on the cards have not been covered during this lesson. Read them anyway; it never hurts to expand your vocabulary!

46. Double check your answers & turn them in!
The End!
Double check your answers & turn them in!

47. Unless otherwise noted, the source for all photographs in this presentation is