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

dhaywick@southalabama.edu

This is a free open access lecture, but not for commercial purposes. For personal use only.