Society of Earth Science Students

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

Meetings:Fridays 1:00 pm Gould-SimpsonBuilding Room 209

Society of Earth Science Students

Meetings:Fridays 1:00 pm Gould-SimpsonBuilding 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-SimpsonBuilding Room 209

Tucson Gem and Mineral Show

Society of Earth Science Students

Meetings:Fridays 1:00 pm Gould-SimpsonBuilding Room 209

Come to the meetingsJoin the field trips

www.geo.arizona.edu/SESS

Free pizza and soda at the first meeting!

Friday September 6th

(Chapter 1 in D & R)(Chapter 1 in D & R)

Overview of Structural GeologyOverview of Structural Geology

OUTLINEOUTLINE 1) What is structural geology?1) What is structural geology?

2) What are structures?2) What are structures? 3) Goals of structural analysis3) Goals of structural analysis

4) Intro. Geometry4) 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

Devil’s Postpile, Sierra Nevada, CA

Joints: fractures with very little or no displacement

Veins: fractures filled with minerals

Secondary Structures cont.

Faults: fractures that have accommodated displacement

Folds: systematically curved layers

Secondary Structures cont.

Cleavage: closely spaced subparallelsurfaces 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 AnalysisGoals of Structural Analysis

Geometry:Geometry: mapping, measurements mapping, measurements

Kinematics:Kinematics: movements related to deformation movements related to deformation– Translation: change in positionTranslation: change in position– Rotation: change in orientationRotation: change in orientation

– Distortion: change in shapeDistortion: change in shape– Dilation: change in volumeDilation: change in volume

Dynamics/Mechanics:Dynamics/Mechanics: relating deformation to relating deformation to stressesstresses

What is it??

What is it?? (interpretation)

Marker bed

faults

drag folds

joints

joints

Intro. Geometry: Structural measurementsIntro. Geometry: Structural measurementsTools: compass and protractorTools: compass and protractor

Planar structuresPlanar structures Strike: compass direction of trace of horizontal line on a plane; Strike: compass direction of trace of horizontal line on a plane;

bearing (quadrant, E or W of north) or azimuth (degrees bearing (quadrant, E or W of north) or azimuth (degrees clockwise from N)clockwise from N)

Dip: inclination of plane from horizontal, perpendicular to Dip: inclination of plane from horizontal, perpendicular to strikestrike

Linear structuresLinear structures Trend: direction of a vertical plane that Trend: direction of a vertical plane that

contains the linear feature in the direction of contains the linear feature in the direction of plunge.plunge.

Plunge: angle between line and horizontalPlunge: angle between line and horizontal

Next Lecture:Next Lecture: Geometry and kinematics ofGeometry and kinematics oflarge-scale deformation- Plate Tectonicslarge-scale deformation- Plate Tectonics

Read Chapter 10 in Davis and ReynoldsRead Chapter 10 in Davis and Reynolds

Important terminology/conceptsImportant terminology/concepts

- Structural geology- what is it and why is it important?- Structural geology- what is it and why is it important?

- Primary structures vs. Secondary structures- Primary structures vs. Secondary structures

- Joints- Joints

- Veins- Veins

- Faults- Faults

- Folds- Folds

- Cleavage- Cleavage

- Foliation- Foliation

- Shear zones- Shear zones

- Lineations- Lineations

- Structural analysis- Structural analysis

- Planar features: strike and dip- Planar features: strike and dip

- Linear features: trend and plunge- Linear features: trend and plunge