Transcript Overview of Structure Geology

A student-run club for all students interested
in Earth Science, regardless of major.
Activities: field trips, weekly speakers,
outreach to kids and adults, and the Tucson Gem
and Mineral Show Junior Education area
Society of Earth Science Students
Meetings:
Fridays
1:00 pm
Gould-Simpson
Building
Room 209
Some past trips:
• Pinacate volcanic
field, Mexico
• Grand Canyon
• Kartchner Caverns
• Moonlight hikes
Society of Earth Science Students
Meetings:
Fridays
1:00 pm
Gould-Simpson
Building
Room 209
Tucson Gem and
Mineral Show
Society of Earth Science Students
Meetings:
Fridays
1:00 pm
Gould-Simpson
Building
Room 209
Come to the meetings
Join the field trips
www.geo.arizona.edu/SESS
Free pizza and soda at the first meeting!
Friday September 6th
Society of Earth Science Students
Meetings:
Fridays
1:00 pm
Gould-Simpson
Building
Room 209
Overview of Structural Geology
(Chapter 1 in D & R)
OUTLINE
 1) What is structural geology?
 2) What are structures?
 3) Goals of structural analysis
 4) Intro. Geometry
What is structural geology?
- Study of rock deformation,
“the study of the architecture
of the Earth’s crust”
- “forensic science”
Why is structural geology important?
- Fundamental to Earth Science
- Insight about planetary evolution
- Relations between tectonics and climate
- Natural hazards
- Resource exploration and management
What skills will be practiced?
- Scientific method
- 3-D Visualization and presentation
- Mapping
- Quantitative
- Integrating multiple disciplines
What are structures?
Two main types:
(1) Primary structures: Develop during formation of a rock body; e.g.,
cross-bedding, ripple marks, mudcracks, pillows (in basalt)
(2) Secondary structures: Form in rocks as a result of deformation- the
structures this class are focused on!
Secondary Structures
Joints: fractures with very little
or no displacement
Devil’s Postpile, Sierra Nevada, CA
Veins: fractures filled with minerals
Secondary Structures cont.
Faults: fractures that have accommodated
displacement
Folds: systematically curved layers
Secondary Structures cont.
Cleavage: closely spaced subparallel
surfaces that impart a splitting property
Foliation: very closely spaced
subparallel planar features
Secondary Structures cont.
Lineations: elongate linear features
Shear zones: “faults with widths”
Secondary Structures cont.
“Microstructures”
Goals of Structural Analysis
 Geometry: mapping, measurements
 Kinematics: movements related to deformation
– Translation: change in position
– Rotation: change in orientation
– Distortion: change in shape
– Dilation: change in volume
Dynamics/Mechanics: relating deformation to
stresses
What is it??
What is it?? (interpretation)
faults
Marker bed
drag folds
joints
joints
Intro. Geometry: Structural measurements
Tools: compass and protractor
 Planar structures
 Strike: compass direction of trace of horizontal line on a plane;
bearing (quadrant, E or W of north) or azimuth (degrees
clockwise from N)
 Dip: inclination of plane from horizontal, perpendicular to
strike
Linear structures
 Trend: direction of a vertical plane that
contains the linear feature in the direction of
plunge.
 Plunge: angle between line and horizontal
Next Lecture: Geometry and kinematics of
large-scale deformation- Plate Tectonics
Read Chapter 10 in Davis and Reynolds
Important terminology/concepts
- Structural geology- what is it and why is it important?
- Primary structures vs. Secondary structures
- Joints
- Veins
- Faults
- Folds
- Cleavage
- Foliation
- Shear zones
- Lineations
- Structural analysis
- Planar features: strike and dip
- Linear features: trend and plunge