1. GLG 101 - Physical Geology Bob Leighty Geologic Structures

2. These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information. To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them. As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, email Dr. Bob if you have any questions about today’s lecture (rleighty@mail.mc.maricopa.edu).rleighty@mail.mc.maricopa.edu Leave no questions behind! Explore and have fun! These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook.

3.  If rocks are subjected to stress, they may be deformed (& show strain)stressstrain undeformed rocks deformed rocks (strain) (stress) compression Stress & Strain Structural Geology

4. Types of Stress Stress & Strain Structural Geology

5. higher T (deeper)lower T (shallow) stronger rocksweaker rocks BrittleDuctile (faulting)(folding) fast strain rateslow strain rate Types of Strain Stress & Strain Structural Geology

6.  Form under brittle conditions by any stress  Fractures with differential offset (vertical and/or horizontal) FW How to ID a fault with vertical offset HW 1)Find matching features on either side of the fault Hangingwall (HW): rocks above the fault plane Footwall (FW): rocks below the fault plane 2) Which way does the HW move?Faults Structural Geology

7.  Normal faults – Tensional stress causes HW  HW  Reverse faults – Compressional stress causes HW  HW  Transform faults – Shear stress causes horizontal movementFaults Structural Geology

8. Faults Unnamed fault on AZ87 (a high-angle normal fault) HW FW South Mountain detachment faultdetachment fault (a low-angle normal fault)

9.  Thrust faults = low-angle (dip <45º) reverse faults Thrust faults HW FWFaults Structural Geology

10.  The San Andreas transform fault (mostly horizontal movement)San Andreas transform faultFaults Structural Geology

11.  Joint: a fracture where no offset has occurred JointJoints Structural Geology

12.  Form under ductile conditions by compressional stressesFolds Structural Geology

13.  Axial plane - splits the fold into two limbsFolds Structural Geology

14. Folds  Strike & dip – describes orientation of bedding Strike & dip

15. dip measuring strike & dip with a compass strike dip strikeFolds Structural Geology

16.  limbs dip in toward axial plane  youngest beds in center of the fold  “point” downSynclinesFolds Structural Geology

17.  “point” up  limbs dip away from axial plane  oldest beds in center of the foldAnticlinesFolds Structural Geology

18.  Folds “plunge” when the fold axis is not horizontal  Form curving outcrop patterns Plunging Folds Folds Structural Geology

19.  A one-limbed fold with horizontal beds on the top & bottomMonoclinesFolds Structural Geology

20.  Dome – A circular upwarp (a circular anticline) Dome Black Hills, SD Structural Domes Folds Structural Geology

21.  Basin – A circular downwarp (a circular syncline) Basin Michigan Structural Basins Folds Structural Geology

22. WWW Links in this Lecture > Stress - http://en.wikipedia.org/wiki/Stress_%28physics%29http://en.wikipedia.org/wiki/Stress_%28physics%29 > Strain - http://en.wikipedia.org/wiki/Strain_%28materials_science%29http://en.wikipedia.org/wiki/Strain_%28materials_science%29 > Faults - http://en.wikipedia.org/wiki/Faultshttp://en.wikipedia.org/wiki/Faults > Dip-slip fault - http://en.wikipedia.org/wiki/Geologic_fault#Dip-slip_faultshttp://en.wikipedia.org/wiki/Geologic_fault#Dip-slip_faults > Strike-slip fault - http://en.wikipedia.org/wiki/Geologic_fault#Strike-slip_faultshttp://en.wikipedia.org/wiki/Geologic_fault#Strike-slip_faults > Detachment fault - http://en.wikipedia.org/wiki/Detachment_faulthttp://en.wikipedia.org/wiki/Detachment_fault > Thrust fault - http://en.wikipedia.org/wiki/Thrust_faulthttp://en.wikipedia.org/wiki/Thrust_fault > San Andreas transform fault - http://en.wikipedia.org/wiki/San_Andreas_Faulthttp://en.wikipedia.org/wiki/San_Andreas_Fault > Joint - http://en.wikipedia.org/wiki/Joint_%28geology%29http://en.wikipedia.org/wiki/Joint_%28geology%29 > Folds - http://en.wikipedia.org/wiki/Fold_%28geology%29http://en.wikipedia.org/wiki/Fold_%28geology%29 > Strike and dip - http://en.wikipedia.org/wiki/Strike_and_diphttp://en.wikipedia.org/wiki/Strike_and_dip > Syncline - http://en.wikipedia.org/wiki/Synclinehttp://en.wikipedia.org/wiki/Syncline > Anticline - http://en.wikipedia.org/wiki/Anticlinehttp://en.wikipedia.org/wiki/Anticline > Dome - http://en.wikipedia.org/wiki/Dome_%28geology%29http://en.wikipedia.org/wiki/Dome_%28geology%29 > Basin - http://en.wikipedia.org/wiki/Basin_%28geology%29http://en.wikipedia.org/wiki/Basin_%28geology%29 Structural Geology