Quiz Seven (9:30-9:35 AM)
UNIVERSITY OF SOUTH ALABAMA
GY 111: Physical Geology
Lecture 20: Rock Deformation
Instructor: Dr. Douglas W. Haywick
Last Time
A) Types of Geological Maps
B) Stratigraphic principles
C) Beds in 3D space; the problem of orientation
D) Strike and Dip
E) Geological maps 1: horizontal and inclined bedding
Web notes 19
Lab Manual Chapter 5
Geology maps
Show the geology at the
surface of the Earth
http://www.geo.ua.edu/Documentation/jpgs/GeoMap.jpg
Quaternary
Geology maps
Tertiary
Q
T
1) Age of rocks
K
Use single (capital) letters to
represent period often followed by
subscripts (rock names)
J
TR
P
IP
M
D
S
O
C
PC
http://www.winona.edu/geology/MRW/mrwimages/geological_time.gif
Geology maps
2) Types of rocks
Use standardized symbols and/or
colors
http://www.rockware.com/rockworks/revisions/litho_plan_02.png
Geology maps
2) Types of rocks
Use standardized symbols and/or colors
http://dept.kent.edu/geology/edlab/structure/GeoMapSymbols.gif
Geology maps
3) Structural Features
4) Bedding Attitude
Use standardized symbols…
… more on this shortly
http://dept.kent.edu/geology/edlab/structure/GeoMapSymbols.gif
Notable Geology maps
USA Geology (simple)
Notable Geology maps
Near Side
Lunar Geology
Far Side
Stratigraphy
Stratigraphy: the study, classification and
correlation of rock layers and layering
Stratigraphic Principles
1) The principle of superposition that states in any sedimentary succession that
has not been overturned, the oldest strata occur on the bottom.
2) The principle of original horizontality that states sedimentary layers are
originally deposited as horizontal sheets
Beds in 3D Space
All sedimentary beds are initially deposited in horizontal sheets (strata). But
you may not initially appreciate this with my 2D cartoons.
Beds in 3D Space
Strike: The orientation of the inclined bed (0 to 360º)
Dip: The inclination of the inclined bed (0 to 90º)
Geological Mapping Symbols
Chalk board
Geological Maps 1
Horizontal bedding leads to fairly simple geological maps (unless you have a
lot of erosion (e.g., the Grand Canyon)
Today’s Agenda
Rock Deformation
A) Confining pressure and rock deformation
B) Elastic versus permanent deformation
C) Types of deformation
D) Test review?
Web notes 20
Lab Manual Chapter 5
Rock Deformation
Rock deformation: any change in the volume, shape or orientation of a
rock body.
Rock Deformation
Orientation (or attitude): sedimentary bedding starts off horizontal, but can
be “deformed” into any configuration.
Law of Original Horizontality
Law of Superposition
Rock Deformation
The strength of materials (including rocks) can be tested in labs using hydraulic
presses. All materials behave elastically up to a point.
Once past the elastic limit, deformation becomes permanent.
Stress & Strain
Stress: a force applied to an area (Example: tire pressure in psi)
Strain: the amount of deformation produced by stress
Elastic strain: analogous to a steel spring or rubber band
Plastic strain: analogous to deforming mud or putty
Brittle strain: analogous to breaking glass
Stress vs. Strain Diagrams
• Illustrate the mechanical behavior of rock materials
• Ductile deformation requires a significant component of
plastic mechanical behavior
Ductile Deformation
Elastic Limit
Stress
Distortion below the elastic limit is
100% recoverable
Strain %
Stress vs. Strain Diagrams
• Illustrate the mechanical behavior of rock materials
• Ductile deformation requires a significant component of
plastic mechanical behavior
Ductile Deformation
Elastic Limit
Stress
Distortion below the elastic limit is
100% recoverable
Strain %
Stress vs. Strain Diagrams
• Illustrate the mechanical behavior of rock materials
• Ductile deformation requires a significant component of
plastic mechanical behavior
Ductile Deformation
plastic
Elastic Limit
Stress
Distortion below the elastic limit is
100% recoverable
Strain %
Stress vs. Strain Diagrams
• Illustrate the mechanical behavior of rock materials
• Brittle: rocks near the surface of the Earth behave as brittle
materials
Brittle Deformation
Elastic Limit
Stress
Distortion below the elastic limit is
100% recoverable
Strain %
Stress vs. Strain Diagrams
• Illustrate the mechanical behavior of rock materials
• Brittle: rocks near the surface of the Earth behave as brittle
materials
Brittle Deformation
Rupture
Stress
Distortion below the elastic limit is
100% recoverable
Strain %
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
Today’s Homework
1. Lecture Test 2 Tuesday
2. Practice recycling!
Next Time
Lecture test
Thursday: Folds (Ductile Deformation)
1.
2.
GY 111: Physical Geology
Lecture 20: Rock Deformation
Instructor: Dr. Doug Haywick
dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposes.
For personal use only.