1. Weathering Forms

2. Weathering 1. Weathering Products 2. Weathering Landscapes

3. 1. Weathering Products Quartz Sand: quartz is one of the last minerals to decay – it survives weathering & erosion to be deposited in

4. Rock Coatings

6. Nutrients - released from mineral weathering Calcium Sodium Magnesium Potassium

7. Clay Minerals Formed

8. Clays represent Earth’s ultimate decay of rock

9. If have too much clay, it shrinks & swells

12. 2. Weathering landscapes Transport-limited landscapes: where the rate of transport (detachment and erosion) is smaller than the rate of weathering. Weathering > Transport Weathering landscapes: where Transport > Weathering

13. The balance between weathering and erosion defines the landscape

14. In deserts – transport is faster

15. You see bedrock, because weathering particles eroded away

16. Humans can upset the balance and accelerate erosion. So when transport (detachment and erosion) becomes faster than weathering, landscapes are not sustainable.

17. Granitic weathering landscapes Consider a common rock – granitic rocks (granite, granodiorite, tonalite, diorite …) made up of interlocking minerals

18. Decay of weak minerals (biotite, feldspar) separates grains and makes granite sand called - GRUS

19. Grus produced most rapidly where joints intersect

20. Grus erosion from joints creates rounded forms at Mt Rushmore

21. Core stones made when corners of granite blocks weathered into grus

23. Core stones in subsurface are “emerge” onto the surface as the grus washes away with rain and flowing water, because they are too big to be carried by water

24. Grus washes away easily with rain, leaving piles of core stones - tors

25. Tors (piled up core stones) very common in the Sonoran Desert

26. Tors often take on significance to people

27. Used core stones in Portugal

28. Granite weathering took a long time in the subsurface (from groundwater) – spheroidal forms were then exposed by erosion of grus

29. Dome forms produced the same way: subsurface weathering in joints Granite that is not heavily joined becomes domes after grus washed away Rio de Janeiro - Sugar Loaf

30. Half dome was made in the subsurface in tropical times and exposed by erosion of grus

31. Karst Topography: entire landscape made by dissolution weathering

32. Other rocks can also dissolve to form karst (gypsum, rock salt)

34. If exposed see grooves (karren)

36. Solution doline – dissolve fastest in joints

37. “Sinkhole” (doline)

38. Can also create doline by collapse

39. Florida – lots of groundwater pumping & roof of cave collapses Before Development After solution doline

40. Sinkholes merge to form Uvale valley

41. “Blind” rivers flow down sinkholes into cavern systems

42. Caves Formation Limestone Cave

43. Caves Features

44. Stalagtite Stalagmite Speleothems: Cave formations

45. Limestone Caves Step 1: Groundwater dissolves limestone, most aggressively at the water table. Also, groundwater follows lines of weakness in the limestone enlarging caves. Step 2. When the water table drops, stalactites and stalagmites can form on the roof and floor, respectively.

46. The water table usually drops when the stream has “cut down” to a lower level

47. Stalagmite – requires lots of time with water table much lower

48. The southeast China karst region has “tower karst” forms