quiz eleven (2:00 to 2:05 pm) - university of south alabama · quiz eleven (2:00 to 2:05 pm) bonus...
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Quiz eleven (2:00 to 2:05 PM)
Bonus Quiz 1
GY 111: Physical Geology
Lecture 28: Faults
Instructor: Dr. Douglas W. Haywick
UNIVERSITY OF SOUTH ALABAMA
Last Time
Web notes 27 Lab Manual Chapter 6
A) Types of folds B) Anatomy of a fold (terminology)
Folds
http://www.parstimes.com/spaceimages/zagros_anticlines.jpg
Folds
Anticlines: Open downwards Synclines: Open upwards
Folds
Folds
Folds are simply bent planes and as such, can be described using strike and dip connotation
Folds
A simple geological map of an anticline
Folds
Folds can be horizontal or plunging
Asymmetrical Folds
Today’s Agenda
Web notes 28: Lab Manual Chapter 7
A) Types of Brittle Deformation B) Types of faults/terminology C) Faults on maps
Faults (Brittle Deformation)
Stress vs. Strain Diagrams • Brittle: rocks near the surface of the Earth behave as brittle
materials
Strain %
Stress
Distortion below the elastic limit is 100% recoverable
Rupture
Brittle Deformation
Mechanical Behavior of Rocks Near-surface rocks that are under low T-P conditions behave as brittle material:
– Fault fracture (slippage) – Joint fracture (no slippage)
Deep rocks under elevated T-P conditions behave as ductile material:
– Folding
Brittle Deformation
When rocks break, one of 3 things can occur:
1) cracking/fracturing 2) jointing 3) faulting
Brittle Deformation
Fractures are irregularly spaced cracks that cut across rocks
http://roamingretirees.wordpress.com/category/state-parksrecreation-areas/
Brittle Deformation
Joints are regularly spaced and parallel fractures that result from tension.
Rectangular jointing is caused by “unloading”
Brittle Deformation
Joints are regularly spaced and parallel fractures that result from tension. Columnar jointing
is caused by cooling
Chalk Board
Brittle Deformation
Faults are fractures that involve movement.
Brittle Deformation
Faults are fractures that involve movement.
Brittle Deformation
Faults come in two main flavors: Dip Slip: movement is in the direction of the dip of the fault plane.
Brittle Deformation
Faults come in two main flavors: Dip Slip: movement is in the direction of the dip of the fault plane. Strike Slip: movement is in the direction of the strike of the fault plane.
Brittle Deformation
A third type of fault involves a combination of both strike and dip movement.
Oblique Slip
Fault Terminology
All faults share some features. All active faults are subject to earthquakes
Chalk Board
Fault Terminology
Dip Slip Faults are subdivided into two types based upon the sense of motion along the fault plane and the type of stress involved Tension = Normal Fault Compression = Reverse Fault
Fault Terminology
Then there is the Hanging Wall and Foot Wall components of faults
Chalk Board
Fault Terminology
Strike Slip Faults are also subdivided into two types based upon the sense of motion along the fault plane. Shear = Strike Slip Fault Left Lateral Strike Slip Fault Right Lateral Strike Slip Fault
Fault Terminology
The most famous strike slip fault in this country is the San Andreas Fault in California
Fault Terminology
Even more impressive is the Alpine Fault in New Zealand
Fault Terminology
Even more impressive is the Alpine Fault in New Zealand
Faults on Maps
Strike Slip Faults (Right Lateral)
Faults on Maps
Normal Faults
Faults on Maps
Reverse Faults
Faults on Maps
There is a special class of reverse fault that is common in mountain belts
Thrust Faults
Faults on Maps
There is a special class of reverse fault that is common in mountain belts Thrust Faults
Faults on Maps
The Canadian Rockies are one of the best places to see thrust faults
Faults on Maps
Trust faults usually occur in multiples (like in the Rockies) leading to complex geological maps
Today’s Homework 1. Assignment 4 (folds on maps) next Thursday
Next Time
GY 302 Poster Session. Tuesday Nov 22 12:00-2:00PM (Bonus) Rock and Gem Show Thanksgiving weekend (Bonus)
proof of attendance required for both bonuses
1) Earthquakes
GY 111: Physical Geology
Lecture 28: Faults
Instructor: Dr. Doug Haywick
This is a free open access lecture, but not for commercial purposes. For personal use only.