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Earth Systems 3209

Earth Systems 3209. Reference: Chapters 4, 15, 16, 19; Appendix A & B. Unit: 4 The Forces Within Earth. Unit 4: Topic 3.2. Faulting/Folding and Deformation. Focus on . . . defining faulting/folding and relating these to the factors that affect deformation.

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Earth Systems 3209

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  1. Earth Systems 3209 Reference: Chapters 4, 15, 16, 19; Appendix A & B Unit: 4The Forces Within Earth

  2. Unit 4: Topic 3.2 Faulting/Folding and Deformation Focus on . . . • defining faulting/folding and relating these to the factors that affect deformation. • describing the different ways faults and folds are classified. • using a drawing to describe the main parts of a fault and a fold.

  3. Faults and Folds • Faulting and folding are two features seen in collision mountains. These features occur when stresses are greater than the strength of the rock and the rock deforms. • Scientist noted that when stress is applied to rocks they first respond by deforming elastically (bending). Once the elastic limit is reached then one of two things happen depending if the rock is in a deep Earth environment or a surface environment:Deep Earth – plastic deformation - resulting in folding or flow. Surface – plastic deformation to elastic limit and then fracture. Text Reference: Pages 421-432

  4. Faults • Fault • a break or crack in Earth’s crust along which movement has occurred. • Three parts of a Fault include: • Hanging Wall - the top part of the rock above the fault plane. • Foot Wall - the bottom part of the rock below the fault plane. • Fault Plane - the surface that separates the two moving pieces. Fault Plane Foot Wall Hanging Wall

  5. Concept of hanging wall and footwall along a fault

  6. Faults • Faults are classified as; • Dip – Slip Faults: • Normal Fault • Reverse Fault • Thrust fault • Horst and Graben • Strike– Slip Faults: • Transform Fault • Right Lateral • Left Lateral

  7. Dip – Slip Faults Diagram: • Different Types of Dip – Slip Faults: • 1) Normal Fault • Caused by tensional forces. • Hanging wall drops in relation to the foot wall. • 2) Reverse Fault • Caused by compressional forces • Hanging wall moves upward in relation to the foot wall Diagram:

  8. Dip – Slip Faults • Different Types of Dip – Slip Faults: • 3) Thrust Fault • Caused by compressional forces • Hanging wall moves up over foot wall • Low angle reverse fault (less 45 degrees) Hanging Wall Foot Wall

  9. Dip – Slip Faults • Different Types of Dip – Slip Faults: • 4) Horst and Graben • Caused by tensional forces. • Horst • An uplifted block of crust bounded by two normal faults. • Graben • A valley formed by the downward displacement of a block of crust bounded by two normal faults. Graben Horst

  10. Strike – Slip Faults • Different Types of Strike – Slip Faults: • 1) Transform Fault • Caused by shearing forces. • Two plates slide side by side • No vertical movement • Two Types: • Left Lateral • Right Lateral Left Lateral Right Lateral

  11. Anticline Syncline Folds • Fold – the bending of rock layers. • caused by compressional forces. • slow, continual, compressional forces, usually at depth, results in ductile deformation (folding). • Parts of a FoldInclude: • Anticline- crust moves upward forming a hill- referred to as an up-fold • 2) Syncline- Crust moves downward forming a valley- referred to as a down-fold

  12. Example 1: Which results from shear forces? (A) anticline and syncline (B) dip-slip faults (C) horst and graben (D) strike-slip faults Which type of stress and faulting occurs at divergent plate boundaries?

  13. Example 2: Based on the diagram, which fault is matched correctly with its corresponding stress?

  14. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Question: With the aid of a clearly labelled diagram, describe the difference between a normal fault and a reverse fault.

  15. Solutions . . . Foot Wall Hanging Wall Question: Answer:A normal fault is formed when tensional forces cause movement within Earth’s crust. The hanging wall moves down with respect to the foot wall. A reverse fault is formed when compressional forces cause movement within Earth’s crust and the hanging wallmove up in relation to the foot wall. Tensional Forces Hanging Wall Foot Wall Compressional Forces

  16. Summary . . . Overview of Points covered: • Fault - a break or crack in Earth’s crust along which movement has occurred. • Parts of a fault • – Hanging wall, Foot wall, and fault plane. • Dip – Slip Faults include • – Normal, Reverse, Thrust, and Horst and Graben. • Strike – Slip Faults • - Transform (Right lateral and Left Lateral) • Fold – bending of rock layers. • Parts of a fold • – Anticline and Syncline.

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