3 agents of erosion and deposition

1. 3 agents of erosion and deposition 1. Water (a) running water- called “Fluvial” (b) subsurface water (c) coastal 2. Wind 3. Glacial ice

2. Fluvial erosion Running water erodes (carries away) earth material (sediment) as 1. overland flow 2. stream flow

3. Causes • Hydraulic power • 2. Abrasion • 3. Corrosion • Dissolution • Hydrolysis

4. STREAMLOAD • Dissolved load • Suspended load • Bedload: • (a) saltation • (b) traction

5. CAPACITY Measure of the amount of solid material a stream can carry

6. COMPETENCE Measure of the particle size which a stream can transport Formula: 2(fs)= 2(c)6 2(flow speed)= 2(competance)6

7. FLOW SPEED Determined by channel conductivity and head gradient Headgradient measures vertical drop per horizontal distance

8. DRAINAGE BASINalso calledWATERSHED

9. DRAINAGE PATTERNS • Dendritic • Trellis • Radial

10. Dendritic Drainage Pattern Satellite photo of fossil drainage pattern in Yemen http://www.star.ucl.ac.uk/~idh/solar/cap/earth/yemen.htm

11. Trellis and Radial drainage patterns http://www.geobop.com/world/Facts/Geography/Water/Rivers/

12. ALLUVIUM: STREAM DEPOSITED DEBRIS Abrams Creek flows on gravel in the alluvial plain and has exposed limestone along the margins of the lower terrace (in background on slope ).  The close-up shows fine alluvial silt above imbricated flat pebbles of metasandstone and phyllite on Abrams Creek.  Pocket knife in center for scale

13. Stream Channel Classification: • Straight • Sinuous • Meandering • Braided

14. Channel patterns are explained by: 1. inside river bend deposition 2. outside river bend erosion 3. levee deposition 4. bottom deposition

15. Straight river channel

16. Sinuous river channel

17. Meandering stream pattern River meanders change with time: Confluence of the Missouri and Yellowstone Rivers Arctic river meanders

18. New Orleans http://www.ces.clemson.edu/semaps/jpeg/9eno/9e2ful.jpg

19. braided stream New Zealand http://stockpix.com/stock/travel/newzealand/9404.htm

20. ENTRENCHED MEANDERS

21. Levee deposition

22. Perennial streams flow all year Mississippi River, Minnesota

23. Ephemeral streams flow after a rain

24. Exotic River origins in wet region; flows through desert or steppe region. Examples: Nile; Colorado; Rio Grande

25. River Delta: depositional terminus of a river. Term= Greek letter, shaped like a triangle. (Note that rivers which terminate in a submerging environment are called estuaries.) Examples: Nile= only example of a “delta” shaped delta! Indus (Pakistan/India border region)= world’s largest. Mississippi (Louisiana)= rapidly laying deposits out into the Gulf of Mexico. Lena (Russia)= flows north to the Arctic Ocean Colorado= 14th largest delta, no longer depositional because no water flows any longer into the Gulf of California… all of the water is captured for cities and agriculture.

26. Huang Ho

27. Huang Ho (Yellow River) World’s siltiest river. Silt from western China (Gobi Desert) is called loess YELLOW RIVER

28. Extreme floods in China • Are explained by: • Bottom deposition • Natural levee deposition • 2000 year history of building levees • Resulting EXTREME levee height… in some areas the river flows 70 feet above the surrounding floodplain!

29. 4 Great Rivers

30. The Nile River

31. The Amazon River

32. The Congo River

33. The Chiang Jiang (Yangtze) River Third longest, third largest by volume of flow.