Understanding Weathering and Erosion in Earth's Formation

1. How do weathering & erosion work together to change the shape of Earth’s surface?

2. Erosion • The movement of rock particles by wind, water, ice, or gravity

3. Weathering • The process that breaks down rock & other substances on Earth’s surface

4. 2 types of weathering: • Mechanical • Chemical

5. Mechanical Weathering • Rock is physically broken into smaller pieces • By the process of: • Freezing & thawing • Release of pressure • Growth of plants • Actions of animals • Abrasion

6. Mechanical weathering can wear away more than whole rock…

7. New mechanical weathering terms: • Abrasion: grinding away of rock by rock particles carried by water, ice, wind, or gravity • Ice wedging: wedges of ice in rocks widen & deepen cracks

8. Chemical Weathering • Breaks rocks down through chemical changes • By the process of: • Water • Oxygen • CO2 • Living organisms • Acid Rain

9. Water… • The most important chemical agent • Water weathers rock by dissolving it

10. How does water assist in weathering & erosion? • Runoff: all the remaining water that moves over Earth’s surface • It picks up soil particles as it moves across the land

11. Rills • Tiny grooves in the soil caused from runoff

12. Gullies • Large grooves, or channel, in the soil the carries runoff after a storm • They flow only after it rains

13. Stream • Channel in which water flows in constantly

14. Tributary • A stream that flows into a larger stream

15. River • A large stream • Rivers erosion creates: • valleys • waterfalls • flood plain • meanders • oxbow lakes

16. Valley

17. Waterfalls

18. Flood Plain • Flat, wide area of land that runs along side a river

19. Meander • Looplike bend in the course of a river

20. Oxbow Lake • A meander that has been cut off from the river

21. River Deposits • Water moves sediments & rocks with it depositing them elsewhere • River deposits create landforms like: • Alluvial fans • Deltas • Soil on a flood plains

22. Alluvial Fan • Wide, sloping deposit of sediment formed where a stream leaves a mountain range

23. Delta • Sediment deposited where a river flows into an ocean • Can be shaped like an arc, triangular, bird’s foot

24. How do sediments enter rivers & streams? • Most washes or falls into the river as a result of mass movement or runoff • Other sediments erode from the bottom or sides of the river

25. Abrasion • Wearing away of rock by a grinding action • Boulders become smaller and smaller as they move down a streambed

26. How much sediment can a river carry? • A load! • Load: the amount of sediment that a river carries

27. Groundwater can create erosion too! • Groundwater: underground water • Stalactite: a calcite deposit that hangs like an icicle from the roof of a cave • Stalagmite: cone shaped calcite deposit growing up from the cave floor

28. What does the amount of runoff depend on? • 5 factors determine the amount of runoff an area receives: • Amount of rainfall • Vegetation • Type of soil • Shape of land • How people use land

29. How does ice change the shape of the land? • Glaciers: large mass of ice that moves slowly over land • 2 kinds: • Valley • continental

30. Valley Glacier • Long, narrow glacier that forms when snow & ice build up high in a mountain valley

31. Continental Glaciers • Glacier that covers much of a continent or island • Much larger than valley glaciers • They cover @ 10% of Earth

32. How do glaciers form? • They form in areas where more snow falls than melts • Snow builds up over time • The pressure compacts the snow into ice

33. How do glaciers move? • Gravity! • Valley glaciers flow a few cm-a few meters each day • Continental glaciers flow in all directions

34. How do glaciers change the land? • Glaciers erode the land through 2 processes called plucking & abrasion

35. Plucking • When a glacier flows over land, it picks up rocks in the process • Rock fragments freeze to the bottom of the glacier

36. Abrasion • As the glacier drags the rocks across the land it gouges & scratches the bedrock

37. What is glacial deposition? • When the glacier melts, it deposits the sediment it eroded from the land creating various landforms • Moraine • Prairie pothole • Kettle Lake

38. Moraine • A ridge formed by the till deposited at the edge of a glacier

39. Kettle • A small depression that forms when a chunk of ice is left in glacial till

40. Wave Erosion

41. Wind Erosion

42. How does gravity assist in weathering & erosion? • Gravity: a force that moves rocks & other materials downhill • Gravity causes mass movement • Mass Movement: any type of process that moves sediment downhill • Ex: landslides, slump, mudflows, creep

43. Landslides • Most destructive kind • Occurs when rock & soil slide quickly down a steep slope • Caused by earthquakes, roadwork

44. Slump • A mass of rock& soil that suddenly slips down a slope

45. Mudflows • Rapid, downhill movement of a mixture of water, rock, & soil • Amount of water can be as much as 60% • Can occur during heavy rains or earthquakes

46. Creep • Very slow downhill movement of rock & soil • It’s barely noticeable • It can tilt telephone poles, fenceposts, or gravestones in weird ways

47. At what rate does rock weather? • Depends on type of rock & climate

48. Type of rock • Permeable: material is full of tiny, connected air space that allow water to seep through it

49. Climate • Average weather conditions in an area • Chemical & Mechanical weathering occurs faster in wet climates • Chemical reactions occur faster in higher temperatures

50. What is soil? • Soil is loose, weathered material on Earth’s surface