1. Weathering

2. Weathering Weathering Landscapes Weathering vs. Erosion
Joints: Setting the Stage
Physical (Mechanical) Weathering
Chemical Weathering
Products and Forms Made by Weathering
Weathering Landscapes

3. 6. Weathering Landscapes
Consider a common rock – granitic rocks (granite, granodiorite, tonalite, diorite …)
made up of interlocking minerals

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

5. Grus produced most rapidly where joints intersect

6. Granular distintegration – seen on rock surfaces

7. rounds edges of petroglyphs – blurring petroglyphs

8. Crumbly distintegration – grains weathered to powder

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

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

12. 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

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

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

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

16. Erosion of weathered material by flaking (fingernail thick)

17. Erosion of weathered material by Scaling – thicker

18. Rock Art Panels Host Dozens of Weathering Forms
How many can you identify?

19. Rock Art Panels Host Dozens of Weathering Forms
How many can you identify?

20. Encourage Site Stewardship to Protect Priceless Cultural Heritage

21. Imagery seen in this presentation is courtesy of ASU faculty, Paradise Valley and Mesa CC faculty, students and colleagues in other academic units, individual illustrations in scholarly journals such as Science and Nature, scholarly societies such as the Association of American Geographers, city, state governments, other countries government websites and U.S. government agencies such as NASA, USGS, NRCS, Library of Congress, U.S. Fish and Wildlife Service USAID and NOAA.