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Unveiling Plate Tectonics: Earth's Dynamic Forces and Movements

Explore the bending and breaking of the lithosphere through plate tectonics, explaining volcanism, seismic activity, and continental movement. Discover the 15 lithospheric plates and types of plate boundaries – divergent, convergent, and transform. Witness the formation of rift valleys, oceanic trenches, volcanic chains, and mountain ranges. Dive into the fascinating world of plate tectonics and its impact on Earth's surface.

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Unveiling Plate Tectonics: Earth's Dynamic Forces and Movements

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  1. Plate Tectonics

  2. Plate Tectonics • Tectonics : bending and breaking of the lithosphere • Plate tectonic theory • explains volcanism, seismic activity, continental movement, folding and faulting

  3. Lithosphere : 15 plates See pp 438-439

  4. Lithospheric plates rest on soft, plastic asthenosphere. • Allows plates to move away from, towards and against one another. • Plate boundaries • Oceanic and continental crust at boundaries

  5. Types of Plate Boundaries: 1. Divergent (Spreading) 2.Convergent 3.Transform

  6. 1. Divergent (Spreading) Boundaries: • plates pull apart a) at oceanic/oceanic crust boundaries (most common) * mid-oceanic ridges (“sea-floor spreading”) on ocean floor b) at continental/continental crust boundaries * rift valleys on land

  7. a) oceanic/oceanic crust boundary

  8. P 426

  9. P 429

  10. a. oceanic/oceanic crust boundary sea-floor spreading: as plates beneath oceans spread, magma wells up from mantle and solidifies as new ocean floor resulting ridge of igneous rock: mid-oceanic ridge (axial rift) (See undersea topography pp. 430 – 431)

  11. b) continental/continental crust boundary • cause continental rupture • rift valleys form • narrow sea may form • new oceans may form • Examples: East African Rift Valley, Iceland rift valley, Red Sea

  12. East African Rift Valley

  13. Iceland

  14. 2. Convergent Boundaries a) at oceanic/continental crust boundary b) at continental/continental crust boundary c) at oceanic/oceanic crust boundary

  15. a) oceanic/continental • Oceanic crust is thinner and denser; it plunges into the soft asthenosphere beneath continent in a process called subduction. • Ocean floor trench forms at subduction zone • On land, a chain of volcanic mountains parallels the subduction zone • Earthquakes • examples: Andes, Cascade Range

  16. Andes

  17. Pacific “Ring of Fire”

  18. b) continental/continental • Plates collide; crustal rocks fold, break, become fused in a suture • mountain chains • Example: Himalayas

  19. c) oceanic/oceanic • Subduction of one plate beneath another • submarine trench and island arc (chain of volcanic islands) • Example: Aleutians

  20. Aleutian Trench

  21. 3. Transform Boundaries • 2 plates move past one another in opposite directions laterally; plates “stick” as they move; tremendous strain builds up and is released in earthquakes • most transform boundaries occur along mid-oceanic ridges, parallel to direction of plate movement • Example: San Andreas Fault

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