Weathering

1. Weathering Do Now: 1. How does the sun play a role in weathering? 2. Describe the similarity between the ways tree roots and ice mechanically weather rock. EQ- How do rocks and minerals break down?

2. Weathering EQ- How do rocks and minerals break down?

3. Weathering http://safari.glynn.k12.ga.us/?a=6856&d=02323AA • Mountains wear down over time. • Due to the Sun’s energy, wind, and water, mountains begin to crumble as soon as they are formed.

4. Weathering • The Smokey Mountains are much older than the Rocky Mountains.

5. Weathering • At one time, the Smokies were as tall as the Rockies and also had sharp peaks.

6. Weathering • Weatheringis simply the chemical and/or physical breakdown of a rock material--weathering involves specific processes acting on rock materials at or near the surface of the Earth

7. Weathering • In other rocks, minerals may slowly dissolve. • Eventually the surface of ALL rocks crumbles, or weathers.

8. Types of Weathering • Mechanical Weathering(physical) • Takes place when rock is split or broken into smaller pieces of the same material without changing its composition. Example: Breaking of a rock cliff into boulders and pebbles

9. WeatheringMechanical • Common weathering processes: • Frost action • Wetting and drying/Wind • Action of plants and animals • Loss of overlying rock and soil

10. Rate of Weathering • The type of rock and climate determine how fast a rock will weather.

11. Types of Weathering • Chemical (decomposition) • takes place when the rock’s minerals are changed into different substances. • Water and water vapor are important agents of chemical weathering. Example: Formation of clay minerals from feldspar

12. Types of Weathering • The two processes of weathering, mechanical and chemical seldom occur alone! • Since water vapor is present in the air everywhere means that chemical weathering occurs everywhere. • Changing conditions of wetness and dryness cause rocks and minerals to break down. • Weathering occurs quickly when running water knocks rocks against each other.

13. Types of Mechanical Weathering • Frost action or Ice Wedging: • Water takes up about 10% more space when it freezes. • This expansion puts great pressure on the walls of a container. • Water held in the cracks of rocks wedges the rock apart when it freezes. • Often occurs in places where temperatures vary from below the freezing point of water to above the freezing point.

14. Types of Mechanical Weathering • Frost action or Ice Wedging con’t • Occurs mostly in porous rocks and rocks with cracks in them • Bare mountaintops are especially subject to ice wedging.

15. Types of Mechanical Weathering Repeated wetted and drying • Especially effective at breaking up rocks that contain clay. • Clays swell up when wet and shrink when dry. • Causes rocks that contain clay, such as shale, to fall apart. • Changing conditions of wetness and dryness cause rocks and minerals to break down. • Weathering occurs quickly when running water knocks rocks against each other.

16. Types of Mechanical Weathering • Plants cause weathering when their roots grow into small cracks in a rock. • Animals cause weathering when they dig into soil or burrow underground. • Action of plants and animals: • Lichens and mosses grow on rocks • They wedge their tiny roots into spores and crevices. • When the roots grow, the rock splits.

17. Types of Mechanical Weathering

18. Types of Mechanical Weathering • Action of plants and animals: • Larger trees and shrubs may grow in the cracks of boulders. • Ants, earthworms, rabbits, woodchucks, and other animals dig holes in the soil. • These holes allow air and water to reach the bedrock and weather it.

19. Types of Mechanical Weathering Exfoliation • Loss of Overlying Rock and Soil • Sheet jointing on a granite outcrop produces cracks in the rock, thereby exposing more of the rock surface to weathering. • Exfoliation is a weathering process that results in rock layers peeling away as they expand or contract.

20. Types of Chemical Weathering • Chemical weathering is the chemical breakdown of rocks. Results mainly from the action of rainwater, oxygen, carbon dioxide, and acids of plant decay. • Moss and lichens on rocks will eventually cause them to break down because of chemicals they release.

21. Agents of Chemical Weathering Oxidation • The chemical reaction of oxygen with other substances is called oxidation. • Oxidation is when the element iron combines with oxygen and water to make rust.

22. Agents of Chemical Weathering Acid Precipitation • Carbon dioxide dissolves easily in water. • It forms a weak acid called carbonic acid • This is the same compound that is in carbonated drinks. • Attacks many common minerals such as feldspar, hornblende, augite and biotite mica. • The original mineral is changed into a clay mineral.

23. Agents of Chemical Weathering • Hollows out great caverns in limestone bedrock.

24. Agents of Chemical Weathering • Acids are formed from the decay of plants and animals. • These acids are dissolved by rainwater and carried through the ground to the bedrock.

25. Agents of Chemical Weathering • Carbon dioxide and sulfur compounds released by industries unite with water in the atmosphere to form acid rain. • Increasing amounts of acid rain in the environment increase the rate of chemical weathering.

26. Factors that affect weathering • Weathering is slowest in dry, cold climates. • Running water speeds up mechanical weathering and chemical weathering. • The kind of minerals found in a rock also affects how fast it weathers. • The greater the surface area of a rock or mineral compared to its volume, the faster it will weather.

27. Weathering The process of breaking down rock. Chemical Weathering Mechanical Weathering exfoliation changes in rock minerals frost wedging root wedging rust wind rock fall running water

28. Activity: Imagine that you are a tin can-shiny, new, and clean. But something happens, and you don’t make it to a recycling bin. Instead, you are left outside at the mercy of the elements. In light of what you have learned about physical and chemical weathering, write a story about what happens to you over a long period of time. What is your ultimate fate?

29. Erosion Do Now: Define chemical weathering and describe its causes. EQ- How do rocks and minerals break down?

30. Chemical weathering occurs when chemical reactions dissolve the minerals in rocks or change them into different minerals. This type of weathering changes the chemical composition of the rock, which can weaken the rock.

31. Erosion EQ- How do rocks and minerals break down?

32. Erosion • Erosion is the process of moving pieces of rock and sediment by wind, water, ice, or gravity.

33. Erosion Moving Sediment • Weathering breaks rock into bits and pieces called sediment. How does sediment get from a mountain peak to a beach?

34. Erosion • Weathering breaks rock into bits and pieces called sediment. • Wind erodes mountains and moves sediment, but not as well as flowing water.

35. Erosion • Running water, wind and ice are all involved in moving sediment. Sediment generally moves downhill because of the force of gravity. • Running water- like that found in rivers, streams, and waterfalls carries sediment. - a river is a large, flowing body of water -a stream is a small river. -a channel is the path that a river or stream follows

36. Erosion Running water moves sediment • The process of depositing sediment after it has been • moved by water, wind, or ice is called deposition. • The amount of sediment carried and deposited by • water depends on many factors: • the volume of water, • the slope of the land, • how rocky or smooth the land is.

37. Erosion Volume: The volume of running water affects how much sediment can be carried. When the volume of flowing rainwater is small, some sediment is moved. After a heavy rainfall, the greater volume of water can move a lot of soil or sediment from yards. Slope: Slope refers to how steep the land is, another word for slope is gradient. The steeper the slope, the faster the water and sediment will move over land. Faster water means that larger particles can be moved and more particles can be moved at one time. Rocky vs. Smooth: Rocky landscapes can trap sediment causing the sediment not to travel far. A smooth landscape or river bed might mean that sediment can be carried a long way.

38. Erosion • A stream table can model how water flows over the land. • The steeper the slope, the faster the water and sediment will move over land.

39. Erosion Sorting sediment: How fast water moves is directly related to how much energy it has. Both the speed of water and its energy are directly related to how big a piece of rock can be moved. Fast, high energy water can move big pieces of rock. Slow-moving water can only move fine sediment. • You can tell the speed of flowing water by the size of the rock pieces found on a stream bottom. • The grains settle in order, making a pattern called graded bedding.

40. Erosion

41. Erosion Interpreting layers of sediment: • Sedimentary rocks hold clues to their past. • If you know the up direction, you know the direction of younging —this is the directions of younger layers.

42. Erosion When sediment is carried by the wind or running water, it often forms a pattern of alternating beds where it is deposited, this pattern is cross bedding. • Cross bedding, is easy to recognize in sedimentary rocks where one layer ends and another layer passed over it.

43. Erosion Moving sediment by ice: • Particles that are trapped in ice or suspended in water can cause weathering. • As the ice of a glacier flows down a valley, it grinds the valley floor with pieces of rock caught up in the ice.

45. As the ice of a glacier flows down a valley, it grinds the valley floor with pieces of rock caught up in the ice.

46. Glaciers are formed from accumulation of snow over hundreds or thousands of years. • As snow piles up and pressure increases, it changes into ice.

47. The fine rock powder that results from glaciers is called “rock flour.” • Rock flour can be washed into lakes and make them a milky blue color.

48. Types of glaciers • Alpine Glaciers (Valley Glaciers) • - small to medium glaciers formed in mountains where the temperature is low enough to prevent snow from melting during the summer. • - Flow slowly down mountain slopes and valleys eroding as they go.

49. U-shaped Valleys Alpine glaciers typically follow a river bed and cut the deep V into a smoother but larger U-shape as they move down the mountain. The sides of the U-shaped valleys are much steeper and rugged than when they were shaped by a river. The ice in a glacier is much more destructive to the land than the running water in rivers.

50. Continental Glaciers • Huge continuous masses of ice that form from layers of snow that compact and freeze into ice.