Not For Web Reproduction. New Topic: TECTONIC GEOMORPHOLOGY. Tectonic Geomorphology vs. Structural Geomorphology

Transcription

1 New Topic: TECTONIC GEOMORPHOLOGY Tectonic Geomorphology vs. Structural Geomorphology Late Cenozoic Tectonic Movement vs. Late Cenozoic Erosion of Older Structures Geologic Time Scale Not For Web Reproduction 1

2 Bloom Ch. 3: Cenozoic Tectonics Also Review Your Geology 101 Notes Erosion Begins with Tectonic Event Hybrid Tectonic-Structural Landforms Old Ideas: Tectonism Controlled by Internal Forces, Independent of Surface Processes. Tectonism Controls Topography Topography Determines Local Climate 2

3 New Ideas: Climate Controls Surface Processes Surface Processes Control Rate of Unroofing Rate of Unroofing Determines Isostatic Rebound Isostacy Is Important Component of Tectonism So Climate Controls Tectonism, too Live Folds - Anticline, Zagros Mtns Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/daac_docs/geomorphology/ GEO_2/GEO_PLATE_T-42.HTML Live Anticline, Breached by Water Gap Live Folds - Consequent Drainage Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/daac_docs/geomorphology/ GEO_2/GEO_PLATE_T-42.HTML 3

4 Zagros Mountains Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/ DAAC_DOCS/ geomorphology/ GEO_2/GEO_PLATE_T- 42.HTML N Zagros Mountains (Image Inverted) Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/ DAAC_DOCS/ geomorphology/ GEO_2/GEO_PLATE_T- 42.HTML Structural Geomorphology Exhumed Folds - Subsequent Drainage Synthetic Aperature Radar (SAR) Image Structural Landscape, Near Harrisburg, Pennsylvania Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/daac_docs/geomorphology/ 4

5 Short, N. M., and Blair, R. W., 1986 Allehgheny Mtns Allehgheny Front Ridge & Valley Great Valley Blue Ridge Homoclinal, Anticlinal and Synclinal Ridges, Pennsylvania Sideling Hill, MD-WV-PA, Synclinal Ridge Wills Mountain (Breached) Anticline Greenland Gap Seneca Rocks Dolls Gap in Saddle Mountain 5

6 Homoclinal, Anticlinal & Synclinal Ridges, near Altoona, Pennsylvania N A S A A A = Anticline S = Syncline S S S A S Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/daac_docs/geomorphology/ Detail near Altoona, Pennsylvania N Homoclinal Ridges, near Rawlings, Wyoming Syncline Anticline Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/daac_docs/geomorphology/ 6

7 Anti-dip Side of Hogbacks, Flinders Range, Australia Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/daac_docs/geomorphology/ Dip Slope of Flatirons, Flinders Range, Australia Delete Slide in 2008 Richât Structure, Mauritania Surface Expression of a Dome Beds dip away from center. Note Fractures. /GEO_2/GEO_PLATE_T-31.HTML 7

8 TECTONIC GEOMORPHOLOGY: FAULTS Earthquakes & Faults Stress: Force Applied Strain: Response to Force Fault Plane of Weakness Along Which Movement Has Occurred Active Fault 1 Quake in 10,000 Y or 2 in 0.5 My Joint Break Without Significant Movement 8

9 Types of Faults Strike-Slip Left-Lateral Right-Lateral Transform Dip Slip Normal Reverse Thrust Hinge Fault Oblique-Slip Strike-Slip Motion Lateral Fault Strike-Slip, San Andreas Fault Photo by G.K. Gilbert, USGS,

10 Right-Lateral Fault Map View - Before Right-Lateral Fault Map View - After Left-Lateral Fault Before After 10

11 Offset Stream Channel, San Andreas Fault, Central Ca Which Type of Lateral Fault? Dip-Slip Motion Fault Parts 11

12 Reverse Fault Before Stress Compression = Squeezing After Thrust Fault, Eastern Pennsylvania Thrust Fault Before Erosion Allocthon (Thrust Sheet) Thrust Fault Autocthon 12

13 Thrust Fault After Erosion Klippe Fenster Geologic Map: Thrust Fault After Erosion Klippe Fenster Thrust Fault After Erosion Klippe Fenster 13

14 Scarp = Escarpment Fault-Line Scarps (= Exhumed Faults) Klippe, Chief Mountain, Montana Dead Tree Photography. All Rights Reserved. Cambrian Rocks Thrust Fault Cretaceous Rocks Used with permission of Dead Tree Photography. May not be reproduced reposted without written permission from Are Fensters, Klippen & Fault-Line Scarps Tectonic or Structural Landforms? Structural! 14

15 Normal Fault Before Stress Tension = Pull-Apart After Tension Normal Fault Tension Normal Fault 15

16 Oblique Fault Before Stress Tension + Shear After Two Tectonic Styles in Normally Faulted Landscape Graben Graben Horst Horst Tilt-Block Mountains & Fault- Angle Valleys 16

17 Dead Sea Rift-Gulf of Aqaba Detail of Basin & Range, Colorado Plateau NV, UT, AZ Sinai Peninsula Gulf of Suez Red Sea 17

18 Graben, Death Valley, CA Cycles of Fan and Pediment Genesis Graben Fault block mtn. alluvial fan, pediment, basin, playa, fault block mtn. Erosion Erosion Depositional Basin Playa Lake 18

19 Lake Playa Salt Flat Playa Salt Pan, Death Valley Martin Miller Photo Source: 5SP-13.jpeg 19

20 After Some Faulting & Erosion Mountain Mountain Front Front Alluvial Fan Pediment Alluvial Fan, Death Valley, California Martin Miller Photo Source: Faulted Alluvial Fan, Panamint Range, Death Valley, California Martin Miller Photo Source: 20

21 Bajada Mountain Front Bajada Alluvial Fan Playa Dune Field Turpan Depression, China After More Faulting & Erosion Mountain Mountain Front Front Alluvial Fan Pediment Photo: John F. McCauley, USGS Inselberg, Mojave Desert, near Baker, California 21

22 Mountain-front sinuosity (S) from Bull and McFadden (1975) paper S = distance along mtn front distance between points Mountain-Front Sinuosity (S) Mountains Basin Mountain Fault Mountain-Front Sinuosity (S) Mountains Basin Old Mountain Front & Fault New Mountain Front 22

23 Mountain-Front Sinuosity (S) Mountains S = distance along mtn. front distance betw. points Mountain-Front Sinuosity (S) Increases w/ Time Mtns Newest Mtn Front Inselbergs S = distance along mtn. front distance betw. points Caracas, Venezuela, Revisited 23

24 Bottle Neck Valleys Triangular Facets or Flatirons Humid, Faulted Landscapes (No Big Alluvial Fans! Why?) 24

25 Lineaments (Photolinears) Produced by Weathered Rock- Fractures, Joints, Breccia, Mylonites, Fault Gouge, etc. Or by Resistant Rock Mineralization (e.g. Geothite) San Andreas Fault Lineament (Photolinear) 25

26 FAULTS: Most earthquake damage is related to landslides or structural failure because of surface waves. Earth seldom opens up and swallows houses, people, cities, etc., but there are accounts of dogs, cows "lost", one guy had his leg trapped Expected Earthquake Intensity See Bloom, 2004, Figure 3-7 Eastern US Neotectonics uplift Uplift (+) & Subsidence (-) mm/yr = m/1000 yr subsidence Source: Bloom, 2004 after Olliver & Brown 1976 uplift subsidence uplift subsidence New Image in

27 Neotectonics Stable Areas = Not So Stable Evidence: Differential Regional Uplift Appalachian Denudation = mm/1000 y Surveying: Parts of Appalachians have Risen 6000 mm/1000 Y vs. East Coast. Uplift in Last 25 My > Uplift betw My Warping of Coastal Plain Seds adjacent to Southern Appalachians Mud Volcano (Diapir) Associated w/ Earthquakes 27