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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 2.7. Plate Boundaries - Transform. Focus on . . . describing a transform boundary.

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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 2.7 Plate Boundaries - Transform Focus on . . . • describing a transform boundary. • drawing a transform boundary which demonstrates the relative motion associated with this boundary.

  3. Plate Boundaries • According to the Plate tectonic theory, three boundaries exist at the edges of tectonic plates. • Divergent Boundary (Ridge) • Convergent Boundary (Trench) • Transform Boundary Text Reference: Pages 526-539 Figure 19.17, pg. 528

  4. Plate Boundaries • Transform Boundary • A transform plate boundary is characterized by two plates grinding past one another without the construction or destruction of crust. • Convection currents exert shear forces on opposing plates forcing them to slide past one another. • Lithosphere is neither created or destroyed at these boundaries.

  5. Transform Fault Fracture Zone Oceanic Ridge (spreading center) Plate Boundaries • Transform Boundary • This type of plate boundary was discovered by J. Tuzo Wilson. Wilson proposed the existence of transform faults to explain the numerous narrow fracture zones and earthquakes found in the crust. • He realized that ridges at divergent plate boundaries were not perfectly linear and came to understand that transform faults exist where segments of ridges are offset (see below). • Most transform faults occur whereoceanic ridges are offset on thesea floor.

  6. Plate Boundaries • Transform Boundary • Earthquakes along such transform faults are shallow focus earthquakes. • One of the largest such transform boundaries occurs along the boundary of the North American and Pacific plates and is known as the San Andreas Fault. Here the transform fault cuts through continental lithosphere.

  7. Plate Boundaries Transform Boundary – Right Lateral “vs” Left Lateral

  8. Plate Boundaries

  9. Example 1: What boundary is NOT associated with volcanic activity? (A) convergent (C) rift(B) divergent (D) transform Which plate boundary does shear forces dominate resulting in tectonic plates sliding past one another?(A) convergent (C) transform(B) divergent (D) subduction

  10. Example 2: What main type of force results in a transform fault? (A) compression(C) elastic (B) shear (D) tensional Which of the following is an example of a transform fault boundary? (A) Alaskan thrust fault (C) San Andreas fault (B) Japan trench (D) Tokyo normal fault

  11. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Question: Which occurs at a transform plate boundary? (A) collision of plates (B) formation of crust (C) sliding of plates along each other (D) subduction

  12. Solutions . . . Question: Which occurs at a transform plate boundary? (A) collision of plates (B) formation of crust (C) sliding of plates along each other (D) subduction

  13. Summary . . . Overview of Points covered: • Transform Boundary: • proposed by Tuzo Wilson • shear forces cause plates slide past on another • right lateral “vs” left lateral • most occur along ocean ridges on the sea floor • no volcanic activity – just shallow focus earthquakes • lithosphere is neither created nor destroyed • example: San Andreas fault

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