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Erosion and Landscape Evolution. Anatomy of a Drainage System.

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Presentation on theme: "Erosion and Landscape Evolution. Anatomy of a Drainage System."— Presentation transcript:

1 Erosion and Landscape Evolution

2 Anatomy of a Drainage System

3 The Continental Divide, Colorado

4 The Ideal Stream Cycle (W.M. Davis, 1880) Not a Literal Time Sequence Youth Maturity Old Age Rejuvenation

5 The Ideal Stream Cycle

6 Youthful Landscape, Utah

7 Young-Mature Landscape, California

8 Mature Landscape, Pennsylvania

9 Monadnock, Colorado

10 Monadnocks, Maine

11 Old Age Landscape, South America

12 Rejuvenation Some change causes stream to speed up and cut deeper. –Uplift of Land –Lowering of Sea Level –Greater stream flow Stream valley takes on youthful characteristics but retains features of older stages as well. Can happen at any point in the cycle.

13 Rejuvenation

14 Rejuvenation, San Juan River, Utah

15 Machu Picchu, Peru


17 The Onset of Old Age? Indiana

18 Why the Stream Cycle Doesn't Explain Everything Changes in sea level during the ice ages Most landscapes have been repeatedly rejuvenated Seems to work best in stable interiors of Africa, Australia and South America.

19 Superposed (Antecedent) Drainage Streams Cut Right Through High Topography Crustal Uplift Across River Rejuvenation Buried Ridge

20 The Ultimate Antecedent Drainage, India-Nepal- Tibet

21 Rejuvenated Peneplain

22 Devil’s Gap, Wyoming

23 The Huang He: “China’s Sorrow” 1887: 2,000,000 dead 1931: 3,700,000 dead 1938: The Chinese dynamite levees to slow the Japanese; half a million Chinese died.

24 River Diversions in the Caspian Region

25 Why is the Danube Blue?

26 Arid and Humid Weathering Compared Rain: Rare, May Be Seasonal, Often Violent Soil: Thin or Absent Vegetation: Sparse-no Continuous Cover Chemical Weathering: Weak Episodic Processes Dominate

27 Arid Erosion Cycle Alluvial Fans Playa Lakes Pediments

28 Alluvial Fans, Utah

29 Old Arid Landscape

30 Deltas

31 Deltas, Greece

32 Yosemite Falls, California

33 Niagara Falls

34 Evolution of Niagara Falls

35 Lakes Limited Lifetime Thousands - Millions of Yr. How They Form: Grabens (Faulting) –Tahoe 1600' –Baikal 5600' –Tanganyika 4000' Scour –Great Lakes to 1300' –Great Slave L. 2000' –Lake Winnipeg Damming: Crustal movement, Landslide, etc. Volcanic Collapse - Crater Lake Sinkholes Kettle Ponds

36 How Lakes Die Eutrophication Infilling - Only Way to Destroy Very Deep Lakes Drainage at Outlet Climate Change

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