GLG310 Structural Geology
Force, Stress, and Strength
[start reading Chapter 3]
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Introduction
Dynamic analysis
Force
Tractions
Stress
Relationships between stress and strain
Deformation experiments
11 March 2016
GLG310 Structural Geology
Structural Geology
• Introduces the physical side of Geological
Sciences and emphasizes
– Geometry (shape, orientation, position, size,
etc.)
– Motion (beginning and ending positions and
paths of particles and bodies—deformation or
change in geometry)
– Mechanics (explanations of why the geometry
and motion are how they are)
3/11/2016
GLG310 Structural Geology
http://gdavis.web.arizona.edu/node/105
Geometric and kinematic description
Structural Analysis
• Descriptive Analysis
– Recognize and describe structures and measure
their locations, geometries and orientations
• Scale, Structural Elements
• Kinematic Analysis
– Focus on motion of materials
• Dynamic Analysis
– Interpret motions in terms of applied forces
4 September 2012
GLG310 Structural Geology
Physical Models
Simulate earth processes in a controlled experiment
Build intuition versus actual prediction
Identify controlling processes or conditions
http://www.youtube.com/watch?v=A5hC47RGq0Y
11 March 2016
GLG310 Structural Geology
http://www.youtube.com/watch?v=xDQRfNEBR2w
11 March 2016
GLG310 Structural Geology
Mechanics
• Develop simple rules to explain behavior
• Can be stated in symbolic or mathematical
terms
11 March 2016
GLG310 Structural Geology
Isaac Newton
Sir Isaac Newton was an English
physicist, mathematician,
astronomer, natural philosopher,
alchemist and theologian, who has
been "considered by many to be the
greatest and most influential
scientist who ever lived.”
F=mA
11 March 2016
Philosophiæ Naturalis Principia
Mathematica, often referred to as
simply the Principia, is a work in
three books by Sir Isaac Newton,
first published 5 July 1687
GLG310 Structural Geology
Force: Newton’s
Laws of Motion
• Law I: Every body continues in its state of
rest, or in uniform motion in a straight
line, unless it is compelled to change its
state by forces impressed upon it.
11 March 2016
GLG310 Structural Geology
http://www.poolplayers.com/instruction/terry-bell/2011/04/billiardsmaster-class-9-approach-and-procedure/ 1:25 cue ball to pool ball
force transfer
Force: Newton’s
Laws of Motion
• Law II: The rate of change of momentum
is proportional to the impressed force and
is made in the direction in which the force
is impressed.
11 March 2016
GLG310 Structural Geology
11 March 2016
GLG310 Structural Geology
Force: Newton’s
Laws of Motion
Dimensional analysis: fundamental units
Mass = amount of material in a body
Weight = Force due to gravity action on a body
1 liter of water has a mass of
on earth it weighs
on the moon it weighs
11 March 2016
GLG310 Structural Geology
11 March 2016
GLG310 Structural Geology
What does a
Newton feel like?
http://www.youtube.com/watch?v=LOINRpWGrlw
What does a
Newton feel like?
-Davis and Reynolds (vo. 2), p. 101
11 March 2016
GLG310 Structural Geology
Force: Forces as vectors
use the tip-to-tail method to find the resultant force
http://www.hk-phy.org/contextual/
http://www.hk-phy.org/contextual/mechanics/for/add_force/resultant_force_e.html
Block mass is 10000 kg
What is normal and
shear force along base?
Dip is 10 degrees.
11 March 2016
GLG310 Structural Geology
Force: Newton’s
Laws of Motion
• Law III: To every
action there is always
opposed an equal
reaction, or the
mutual actions of two
bodies on each other
are always equal in
magnitude and
opposite in direction
http://www.hk-phy.org/contextual/
Force: Newton’s
Laws of Motion
• Law III: To every
action there is always
opposed an equal
reaction, or the
mutual actions of two
bodies on each other
are always equal in
magnitude and
opposite in direction
Equilibrium
11 March 2016
GLG310 Structural Geology
Driving and
resisting forces of
plate tectonics