Understanding Weathering: Physical and Chemical Processes Explained

1. Lesson 1 Weathering

2. Types of Weathering… 1. Physical weathering … rocks & minerals break down into smaller pieces. http://www.kidsgeo.com/geology-for-kids/0066-mechanical-weathering.php

3. Physical Weathering… a. Frost wedging … water in cracks expands as it freezes, wedging the rock apart & splitting it! http://mail.colonial.net/~hkaiter/wxerosglacier.html http://www.gly.uga.edu/railsback/FieldImages/ClavaWeathering.jpeg

4. Physical Weathering… • Exfoliation… overlaying rocks removed by erosion, pressure reduced, outer layers crack & are stripped away. • This can also occur due to land rebound after a glacier melts. http://hays.outcrop.org/GSCI320/lecture3.html

5. Chemical Weathering 2. Chemical weathering is the process by which… rocks / minerals undergo changes in composition as result of chemical reactions. (change chemically) Water is a major factor in weathering. http://i.ehow.co.uk/images/a05/ne/08/factors-affect-chemical-weathering-1.1-800X800.jpg

6. Chemical Weathering: Water a. Water… It dissolves minerals and rocks. This results in the formation of clayminerals. kaolinite Clay comes from felsic rocks and can be molded and heated into pottery.

7. Chemical Weathering: Oxygen b. Oxygen in atmosphere combines with iron in rocks & minerals.This results in rust (red rocks).

8. Chemical Weathering: Carbon Dioxide Carbon Dioxide… It combines with water (H2O) in atmosphere or soil forming weak carbonic acid. This results in clay or caves.

9. Chemical Weathering: Acid Precipitation • Acid precipitation … rain, snow, sleet mixed with gases in the atmosphere that turn these forms of water into a weak acid (pH < 5.0). • sulfur dioxide and nitrogen oxide • The most common source – coal-fired power plants • It is also known as acid rain, • It causes lakes to become more acidic than living things can handle. AND… It chemically weathers nonliving things like statues and buildings See next slide…

10. Factors That Affect Weathering…Climate • Chemical weathering occurs most rapidly in climates that are… warm & humid. Places such as Central America and S.E. Asia (tropical places). Note the intensely weathered soil. http://www.geotimes.org/july08/trends1.jpg

11. A. Factors That Affect Weathering…Climate • Physical weathering occurs readily in climates that can get cold. In the winter places such as the Appalachian Mountains experience frost wedging.

12. http://www.travelpod.com/travel-blog-entries/gensphoto/1/1280057679/tpod.htmlhttp://www.travelpod.com/travel-blog-entries/gensphoto/1/1280057679/tpod.html B. Factors That Affect Weathering…Rock Type and Composition • Sedimentary rocks are more easily weathered than… • …harder igneous and metamorphic rocks. • The fall line is created by harder, erosion-resistant rock gives way to easily-eroded rock of coastal plains.

13. C. Factors That Affect Weathering… Surface Area • As pieces of minerals & rocks get smaller, their surface area increases. • This speeds chemical weathering b/c more total surface area is available for chemical weathering. • Draw p. 162. http://www.mrsciguy.com/sciimages/surfacearea.jpg

14. D. Factors That Affect Weathering… Topography http://www.geoproducts.org/App-SlopeErosionControl.aspx • Materials on level (flat) areas are likely to remain in place as they undergo changes. • Material on slopes have a greater tendency to move as a result of gravity. Controlling weathering/erosion on slopes can be big business!

15. Lesson 2 Erosion by Running Water

16. Introduction… 1. What is erosion? • process that transports Earth’s materials from one place to another 2. Why is gravity associated with many agents of erosion? • It pulls all materials down slope! Five forces or agents of erosion include: running water, glaciers, wind, gravity, and human activity. http://www.awi.de/en/news/press_releases/detail/item/scientists_expect_increased_melting_of_mountain_glaciers/?cHash=10a73716ccb3df05543dca09d1f65e50

17. Erosion By Running Water… 1.Water has more power than wind to move large objects. • Rill erosion… small channels carved by water form on the side of a slope. • Gully erosion… a rill becomes deep and wide. http://www.soils.umn.edu/academics/classes/soil2125/img/10riller.jpg Gully Erosion http://plantandsoil.unl.edu/croptechnology

18. Erosion by Running Water… http://www.learner.org/courses/envsci/visual/visual.php?shortname=gully_erosion 4. Gully erosion is usually caused when too much vegetation is removed.

19. Erosion by Running Water… • Rocks exposed to their surrounding environments are slowly weathered away then… streams andrivers carry these sediments to coastal areas. The Nile River http://earthasart.gsfc.nasa.gov/mississippi.html http://www.sciencekids.co.nz/pictures/earth/nileriverdelta.html

20. 6. Canyon Erosion in Canyonlands National Park, UT

21. Waves erode rocky coastlines…

22. Deposition by Running Water… http://farm1.static.flickr.com/121/259022625_5073e03db2.jpg 1. The Mississippi River carries sediment into the Gulf of Mexico. • It drains about 43% of the USA! • It drains the land west of the Appalachians and east of the Rockies.

23. The Mighty Mississippi! http://www.nps.gov/miss/riverfacts.htm

24. Deposition by Running Water… 2. Deltas are formed when rivers deposit sediments in the mouth of a bay or gulf. • This forms a triangular-shaped deposit. • New Orleans is built on the Mississippi Delta.

25. Deposition by Running Water… • An alluvial fan is… a fan-shaped deposit that forms when running water carries sediment through a narrow mountain valley.

26. Deposition by Running Water… www.skywalker.cochise.edu Eroded olivine forms a green sand beach in Hawaii.

27. Deposition by Running Water… Eroded basalt forms a black sand beach in Hawaii.

28. Deposition by Running Water… Eroded limestone forms a white sand beach in Florida.

29. Lesson 3 Erosion by Glaciers

30. http://www.geocaching.com/seek/cache_details.aspx?guid=50953ee7-2a7a-4cf9-b8f5-964ec62c8913http://www.geocaching.com/seek/cache_details.aspx?guid=50953ee7-2a7a-4cf9-b8f5-964ec62c8913 Introduction… 1. Glaciers change Earth’s surface by… • scrape & gouge out large sections of land. • carry huge rocks & debris piles over great distances • Polish surfaces http://www.physicalgeography.net/fundamentals/10af.html Glacial Grooves on Kelly’s Island in Lake Erie (one of the great lakes!)

31. Introduction:Glacial Erosion… 2. Many features of glacial erosion are found in the states of New England and the Midwest. This is an esker – a landform left by glacial erosion in the Adirondacks. http://merryatsyracuse.blogspot.com/2010/09/stillwater-esker.html

32. http://www.geographypages.co.uk/a2glac.htm Introduction: Glacial Erosion… 3. What is a glacier? • A large moving mass of ice! • Glaciers are the most powerful erosive force on Earth. travelpod.com The Jungfrau Glacier in Switzerland

33. Introduction: Glacial Erosion… 4. There are two types of glaciers. A valley glacier forms in mountainous areas • Valley glaciers will carve U-shaped valleys. • Valley glaciers are found in the Rocky Mountains. Valley glaciers in the Rocky Mountains

34. Introduction: Glacial Erosion… 5. A continental glacier covers large continent sized areas. • They are also called ice sheets. • Examples include Greenland and Antarctica. http://web.arc.losrios.edu/~borougt/ContinentalGlaciers.gif

35. Glacial Erosion… 1. Glacial erosion can carve out the following features… • Cirque – a bowl shaped depression • Arête – sharp, steep ridge • Horn – pyramid-shaped peaks Glacial Features online… http://rst.gsfc.nasa.gov/Sect17/Sect17_5a.html http://www.scienceclarified.com/landforms/Faults-to-Mountains/Glacial-Landforms-and-Features.html

36. 2. Glacial Grooves… • Caused by … glaciers plucking up large rocks and dragging them over the bedrock.

37. Glacial Deposition… 1. Glacial till is the mixed debris that glaciers carry embedded in their ice. 2. A moraine is a ridge of till that’s been bull-dozed by a glacier. http://rst.gsfc.nasa.gov/Sect17/moraine.jpg

38. Glacial Deposition… 3. An outwash plain is a plain where glacial melt water and debris are deposited. http://rst.gsfc.nasa.gov/Sect17/outwash_plain_DDS21_Cooper_river_region_Alaska.jpg

39. Glacial Deposition… 4. Two types of lakes formed by glaciers include… Kettle lakes and cirque lakes • Our most famous lakes are the Great Lakes which are moraine-dammed lakes • Huron, Ontario, Michigan, Erie, Superior See next 2 slides for pictures…

40. Lesson 4 Erosion By Wind

41. Introduction… http://www.saharamet.com/desert/photos/photos.html 1. Where is wind a major erosional force? • In deserts (hot and dry) AND…

42. Introduction… … and incoastal areas.

43. Introduction… http://www.sci.uidaho.edu/scripter/geog100/lect/12-wind-deserts/12-wind-deserts.htm 2. How do plants guard against erosion? • Their roots hold onto soil & keep it from blowing away.

44. Introduction … http://www.forestry.ok.gov/windbreaks-shelterbelts 3. Windbreaks - tall plants grown perpendicular to direction of wind to keep soil from blowing away Windbreaks in Oklahoma

45. Introduction … 4. How is wind erosion different from water erosion? • It can transport sediment uphill!

46. Wind Erosion… http://www.sci.uidaho.edu/scripter/geog100/lect/12-wind-deserts/12-wind-deserts.htm http://www.calstatela.edu/dept/geology/Deserts/TrackDesertPavement(2).jpg 1. Deflation … lowering of land due to the wind removing surface particles. The coarse surface left behind is called desert pavement.

47. Wind Erosion… 2. The Dust Bowl was created by… • A severe drought • Poor farming practices in which large areas of natural vegetation was removed • Strong winds picked up surface particles

48. Wind Erosion… 3. Abrasion… Wind-blown sand sand-blasts surface of rocks Ventifacts… rocks shaped by wind-blown sediments http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/eolian_systems/features_wind_erosion.html We drove past this ventifact sculpted by the wind in Utah!

49. Wind Deposition… http://static.newworldencyclopedia.org/7/73/Sand_dune_formation.png 1. A sand dune is… a pile of wind-blown sand. Four conditions determine a sand dune’s shape… • Amount of sand • Wind direction • Wind speed • Amount of vegetation

50. Wind Deposition… http://www.igsb.uiowa.edu/Browse/loeshill/loeshill.htm • Loess are thick wind-blown silt deposits (silt dunes). • Loess deposits are found in the Midwestern states: Illinois, Iowa, Missouri, S. Dakota, Nebraska, Kansas, and Indiana. • They are used as farmlands because they are so fertile. Loess Hills in Iowa