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Internal Forces and Climate Chapter 2 Lago Atitlán, Guatemala Lachniet, 2009.

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Presentation on theme: "Internal Forces and Climate Chapter 2 Lago Atitlán, Guatemala Lachniet, 2009."— Presentation transcript:

1 Internal Forces and Climate Chapter 2 Lago Atitlán, Guatemala Lachniet, 2009

2 Figure 2-1 The Endogenic Effect The Earth has relief Two main levels: land surface and sea floor Without endogenic processes, exogenic processes would weather the earth to a state of minimum relief.

3 Tectonism Driven by endogenic processes Orogenic –Structural mountain formation –Rocky Mountains Epeirogenic –Uplift, warping, disruption –But not folding or thrust processes –Colorado Plateau

4 Rates Uplift and tectonism –Most rapid –Episodic Denudation (erosion) –Slower but steadier –Rate governed by climate

5 Uplift rates Change over time as masses approach equilibrium Shorelines on the coast of Greenland had rapid uplift following deglaciation Slowing to the present Figure 2-3

6 Neotectonics Recent or active tectonism Black Hills fault, Boulder City (Eric Fosset, UNLV M.S.) Eric Fosset, photo

7 Geomorphic Expression of Normal Faulting Tilted fault-block mountains Basins and Ranges (Horsts and Grabens) Large offsets: –Sierra Nevada: 3300 m –Grand Tetons: 7500 m –Red Rock Canyon (ss bluff): 1100 m

8 Fault-bounded mountain Age of faulting inferred from sinuosity of mountain front Sinuosity (J) = ratio of real (L j ) versus straight-line (L s ) distance across front Highly active faulting J = 1.0- 1.5 Inactive faulting J = 3-10 Figure 2-4

9 From AGI, 2003. Laboratory Manual in Physical Geology, (Ed. Busch), sixth edition. Basin and Range landforms

10 Las Vegas Valley Las Vegas Valley. Foto: Lachniet (2003)

11 Geomorphic evidence of faulting Offsetting of land surface –Laterally: strike-slip –Vertically: Normal, thrust faulting Fault scarps Differential Erosion Triangular Facets Drag Folding

12 Fault Scarps Steep linear bluffs along fault Vertical motion Often record multiple offsets (~1-10 m) Fault Scarp Evolution Steepness of scarp related to age and activity Fresh scarps are steep Old scarps are less steep

13 Fault scarp on alluvial fan Death Valley National Park, CA. Photo by Stephen Hlowjski, 2004 Displacement

14 Fault Scarp Evolution Denudation Follows Orogeny Episodic mountain building from endogenic processes (episodic and rapid), followed by gradual but steady erosion. Figure 2-5 Triangular Facets

15 Triangular Facets along the Wasatch Fault, Utah (W.K. Hamblin) Characteristic of Normal faulted blocks Represent the scarp face Incised by stream erosion

16 Drag folds – many fault types Las Vegas Valley shearzone

17 Landforms associated with strike-slip Faulting

18 Shutter Ridges

19 Carrizo Plain Photo: Garret Speeter, 2005

20 San Andreas Fault photo by Robert E. Wallace Stream Offset, San Andreas Fault, Carrizo Plain, CA

21 Shelton Linear Ridges Linear Valley or trough San Andreas fault. California

22 Shelton Sag pond on trace of 1906 break along San Andreas fault. California

23 Springs/trees associated with fault

24 Thrust faulting landforms Low angle Stratigraphic Inversion possible Klippes –Erosional remnants of overthrust rock Scarps Ragged outlines of thrust sheet extent

25 Keystone thrust, Las Vegas

26 Keystone Thrust Photo Lachniet 2007

27 Klippe

28 Deformed surfaces and uplift Examples include –Stream terraces –Beach terraces Surface slopes don’t follow the ‘typical’ slope –Upwarping along center of deformation axis Figure 2-11

29 Climatic Geomorphology Landforms characteristic of certain climates –Temperature, precipitation amount, precipitation type, winds Also driven indirectly by changes in sea level –From both isostatic adjustment of continents, and ice volume on land Relict landforms indicate past climates –Example: glacial deposits in Missouri Table 2-3 Figure 2-15

30 Quaternary Climate Change Paleoclimatology (GEOL 437/637) Glacial to interglacial climates –5 to 10 o C annual temperature change –100,000-year Ice-Age cycle –Last full glacial period only 21,000 yr ago –Sea level falls when glaciers grow –This drives incision and base level lowering Great Basin was wetter than today

31 Late Quaternary Climate Change

32 North America 21,000 years ago Modern winter jet stream Last Ice Age Winter jet stream Laurentide Ice Sheet Cordilleran Ice Sheet

33 Climate Influence on Rivers The effects of climate are manifested through geological and vegetation ‘filters’ Figure 2-19

34 Extra Slides

35 The V f ratio Ratio of the width (W vf ) of the valley floor divided by the relief of the valley walls –Incision from active tectonics results in very low values (0.5 to 0.05). –Larger values = less tectonism Relief – distance between local high (A ld, A rd ) and low spot (A sc ) Vf = W vf ÷ ((A ld,- A sc ) + (A rd,- A sc )/2) Figure 2-7

36 Tilted fault block mountain Spring Mountains, S. Nevada. Foto: Lachniet (2004)

37 Black Mountains fault scarp

38 San Andreas Fault

39 Ground offset

40 Shelton Trees mark where San Andreas fault crosses stream bed Offset River channel San Andreas Fault

41 Carrizo Plain Photo: Garret Speeter, 2005

42 Carrizo Plain Photo: Garret Speeter, 2005

43 Keystone Thrust Photo Lachniet 2007

44 Keystone Thrust

45 River responses to climate Cold climates need less rainfall than warm climate to produce a similar quantity of sediment I.e., cold climates are more erosive Figure 2-17, for basins in the western United States

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