Weathering & Erosion: 7th Grade Geography Teacher Guide

1. Weathering and Erosion – PASS Preparation Teacher Guide This activity is designed to familiarize students with the concepts of physical and chemical weathering and erosion. This is accomplished through providing greater insight and representative examples for a weathering and erosion table of information. Examples of questions on this topic can be found on page 21 of the Oklahoma PASS Social Studies Test Preparation Workbook – Middle Grades Level. Overview NCGE Standards Physical Systems: STANDARD 7: The physical processes that shape the patterns of Earth's surface.Environment and Society: STANDARD 14: How human actions modify the physical environment. PASS Objectives 7th Grade World Geography: STANDARD 3: The student will examine the interactions of physical systems that shape the patterns of the earth’s resources. STANDARD 5. The student will examine the interactions of humans and their environment.   Grade Level Seventh Grade GIS Skill Level No GIS knowledge is necessary Time One 50-minute class period for completion of activity. Materials: This activity requires personal computers with Microsoft PowerPoint. Sources: Wikipedia http://www.wikipedia.org Weathering and Erosion – PASS Preparation Teacher Guide

2. Weathering and Erosion p. 21 Oklahoma PASS Social Studies Test Preparation Workbook Middle Grades Level

4. Weathering • The process of decomposition and/or disintegration of rocks, soils and their minerals through natural, chemical, and biological processes. • It is not to be confused with erosion, which is the movement of rocks and/or weathered products by water, wind, ice or gravity. Source: Wikipedia.org

6. What it does: Mechanical Weathering • “Physically breaks down large pieces of rocks” • The cause of the disintegration of rocks. • Most of the time, it produces smaller angular fragments (like scree). • Chemical and physical weathering often go hand in hand. For example, cracks exploited by mechanical weathering will increase the surface area exposed to chemical action. Furthermore, the chemical action taking place in cracks can aid the disintegration process.Source: Wikipedia.org

7. Scree Source: Los Alamos National Laboratory Source: Los Alamos National Laboratory

9. Mechanical Weathering Examples “Frozen water expands and enlarges cracks” Example of mechanical weathering on a glacial transported boulder. Source: Department of Geology and Geophysics, University of Wisconsin.

11. Mechanical Weathering Examples “Seeds fall into cracks and grow into trees that split the rocks” Source: USGS

13. Chemical Weathering • “Changes a rock’s chemical makeup” • A change in the chemical composition of rock • Requires the presence of water to some degree • Principal agents are: 1. water 2. oxygen 3. CO2 (carbon dioxide)

15. Chemical Weathering Examples “Acid created by water and carbon dioxide can dissolve rocks” The surface pattern on this pedestal rock is honeycomb weathering, caused by salt crystallisation. This example is at Yehliu, Taiwan. Planet Geography 3rd Edition (2005). Source: Wikimedia Commons.

16. Chemical Weathering Examples “Acid created by water and carbon dioxide can dissolve rocks” A freshly broken rock shows differential chemical weathering progressing inward. This piece of sandstone was found in glacial drift near Angelica, New York. Source:Wikipedia.org

18. Chemical Weathering Examples “Acid rain eats away rock surfaces” Source: DHD Multimedia Gallery

19. Discussion Slide:More weathered vs. less weathered hieroglyphics

20. Discussion Slide:Stone test wall The stone test wall was constructed to study the performance of stone subjected to weathering. It contains 2352 individual samples of stone.

21. Discussion Slide: Cave formation

23. Erosion • The displacement of solids (soil, mud, rock, and other particles) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). • Although the processes may be simultaneous, erosion is to be distinguished from weathering, which is the decomposition of rock. • Erosion is an important natural process, but in many places it is increased by human land use. Some of those poor land use practices include deforestation, overgrazing and road or trail building. Source: Wikipedia.org

25. What It Does – Erosion by Moving Water • “Cuts into rock and wears it away” • Erosion is both downward, deepening the valley, and headward, extending the valley into the hillside. • In the earliest stage of stream erosion the erosive activity is dominantly vertical, the valleys have a typical V cross-section, and the stream gradient is relatively steep. When some base level is reached the erosive activity switches to lateral erosion which widens the valley as the stream meanders across the valley floor. Source: Wikipedia.org

27. What It Does – Erosion by Moving Water • “Carries pieces of rock to other places” • In all stages of stream erosion by far the most erosion occurs during times of flood when more and faster moving water is available to carry a larger sediment load. Source: Wikipedia.org

28. Erosion – Moving Water Example “Erosion is an important natural process, but in many places it is increased by human land use.” Source: Wikipedia.org Source: Wikimedia Commons Source: USDA

30. Erosion – Moving Water Examples “Carves canyons and valleys” Source: Photo-net

32. Erosion – Moving Water Examples “Creates Flood Plains and Deltas” Source: Stephen Codrington. Planet Geography 3rd Edition (2005)

33. Erosion – Moving Water Examples “Creates Flood Plains and Deltas” Source: NASA

34. Erosion – Moving Water Examples “Creates Flood Plains and Deltas” Deltaic deposits of the Carboniferous era can be seen in this roadcut on Rte 15 just north of Williamsport, Pennsylvania. Cross bedding and discontinuities can be seen. The era is referred to as carboniferous, because coal deposits are associated with these rock formations. Source: Wikipedia.org

36. What It Does – Erosion by Wind • “Carries soil away and deposits it elsewhere” • Also known as eolian erosion, this is the movement of rock and/or sediment by the wind. The wind causes dust particles to be lifted and therefore moved to another region. • Wind erosion generally occurs in areas with little or no vegetation, often areas where there is not enough rainfall to support vegetation. • Windbreaks are often planted by farmers to reduce wind erosion.

38. Erosion – Wind Examples “Dust Bowls are formed by loss of soil” Source: USDA NRCS

39. Erosion – Wind Examples “Dust Bowls are formed by loss of soil” Source: USDA NRCS

41. Erosion – Wind Examples “Rich farmland is created by new deposits of soil” Cornfield on loess soil in Iowa. Source: University of Iowa

42. Erosion – Wind Examples “Rich farmland is created by new deposits of soil” Loess in Hungary has traveled by wind from Asia. Source: Wikipedia.org

44. What It Does – Erosion by Glaciers (Ice) • “Carry, dirt, rocks and boulders” • “Wear away land” • Glaciers erode the terrain principally through two methods: abrasion and plucking. • As the glacier flows over the bedrock's fractured surface, it lifts blocks of rock that are brought into the ice. This process is known as plucking, and it is produced when subglacial water penetrates the fractures and the subsequent freezing expansion separates them from the bedrock. When the water expands, it acts as a lever that loosens the rock by lifting it. This way, sediments of all sizes become part of the glacier's load. • Abrasion occurs when the ice and the load of rock fragments slide over the bedrock and function as sandpaper that smoothens and polishes the surface situated below. Source: Wikipedia.org

45. Erosion – Glacier Examples “Carry dirt, rocks, and boulders” “Wear away land” Plucking. Can you tell which way the ice was flowing? Source: NOAA

46. Erosion – Glacier Examples Source: Wikimedia Commons “Carry dirt, rocks, and boulders” “Wear away land”

47. Erosion – Glacier Examples Glacial striations. Source: University of Washington Glacial striations. Source: Ohio Wesleyan University “Wear away land”

49. Erosion – Glacier Examples “Carved out the Great Lakes” Source: US Army Corps of Engineers

50. What It Does – Erosion by Waves and Currents • Shoreline erosion, on both exposed and sheltered coasts, primarily occurs through the action of currents and waves, but sea level change can also play a role. Source: Wikipedia.org