2. WEATHERING GEOLOGY NOTES Chapter 5

3. WEATHERING 4 Breakdown of rock due to weather 4 no visible motion

4. MECHANICAL (PHYSICAL) WEATHERING 4 Disintegration 4 Breaks into small pieces 4 NO visible motion

5. MECHANICAL WEATHERING 4 Ice (frost wedging) –water expands when freezes –angular pieces

8. MECHANICAL WEATHERING 4 Sheeting(exfoliation) –pressure is removed from above –Fractures “peel” off

10. Half-dome

11. MECHANICAL WEATHERING 4 Other types –burrowing animals –Plant roots –Mud cracks

12. Mudcracks 4 When water evaporates- mud shrinks

13. CHEMICAL WEATHERING 4 Decomposition 4 chemical change takes place

15. CHEMICAL WEATHERING 4 Hydrolysis 4 reacts with acid/water to form clays 4 feldspar + carbonic acid + water clay + soluble minerals 4 common in granite

16. CHEMICAL WEATHERING 4 DISSOLUTION ANY CARBONATE + CARBONIC ACID CALCIUM CARBONATE (soluble) –common in limestone –creates caves and sinkholes

17. Parthenon, Greece

18. sinkholes

19. Sinkhole formation

20. Areas prone to sinkholes

23. 4 Marble statue Dissolution

24. CHEMICAL WEATHERING 4 OXIDATION –reacts with O 2 – Groundwater with Fe is powerful agent –minerals with high Fe content hematite, limonite, olivine intense in tropical climates

25. Oxidation of basalt

26. Pictured Rocks, MI

27. PLANES OF WEAKNESS 4 WHERE ROCKS WILL BREAK –Joints- vertical fractures –bedding planes- horizontal fractures –Granular disintegration- cement in clastic rocks breaks down

28. joints

29. BEDDING PLANES

30. Granular disintegration

31. ROCK TYPES 4G4Granite - exfoliation, hydrolysis (k-spar to clay) –q–quartz doesn’t weather 4B4Basalt- chemical (oxidation) 4S4Sandstone- granular disintegration 4l4limestone- dissolution 4s4shale- breaks down into clay

32. Sandstone tombstone

34. Granite

35. Which rocks weather most rapidly? 4 sedimentary

36. Which rocks are most resistant to weathering? 4 Igneous / metamorphic (exception?) 4 Bowen’s reaction series –Olivine most

38. Differential weathering 4 Different rock types weather differently 4 OR 4 Different rates of weathering due to exposure

39. Stairway to heaven, CO

40. Bryce Canyon, UT

42. arches

43. Differential erosion limestone shale

44. Hoo-doos

45. CLIMATE AND WEATHERING 4 Chemical- warm and moist 4 Physical- freeze/thaw cycle

46. CLIMATE 4 TROPICAL –Strong chemical 4 DESERT –Slight mechanical 4 POLAR –Slight mechanical 4 MID LATITUDE (MI) –Strong chemical and mechanical