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PLATE TECTONICS AND BOUNDARIES

PLATE TECTONICS AND BOUNDARIES. How do we know what the Earth is made of?. Geophysical surveys: seismic, gravity, magnetics , electrical, Earth size and shape Acquisition: land, air, sea and satellite Geological surveys: fieldwork, boreholes, mines. Plate Tectonics.

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PLATE TECTONICS AND BOUNDARIES

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  1. PLATE TECTONICS AND BOUNDARIES

  2. How do we know what the Earth is made of? • Geophysical surveys: seismic, gravity, magnetics, electrical, Earth size and shape • Acquisition: land, air, sea and satellite • Geological surveys: fieldwork, boreholes, mines

  3. Plate Tectonics • The Earth’s crust is divided into 12 major plates which are moved in various directions. • This plate motion causes them to collide, pull apart, or scrape against each other. • Each type of interaction causes a characteristic set of Earth structures or “tectonic” features. • To determine which type of boundary is present, scientists use evidence of earthquakes and volcanoes

  4. World Plates

  5. Three types of plate boundary • Divergent • Convergent • Transform

  6. Divergent Boundaries • Spreading ridges • As plates move apart new material is erupted to fill the gap

  7. Mid-Atlantic Ridge = Divergent Boundary

  8. http://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeghttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

  9. Iceland: An example of continental rifting • Iceland has a divergent plate boundary running through its middle

  10. Convergent Boundaries • Plates move toward each other • There are three typesof convergent plate boundaries • Continent-continent collision • Continent-oceanic crust collision • Ocean-ocean collision

  11. Continent-Continent Collision • Forms mountains,e.g. European Alps, Himalayas

  12. Collision Zones Two continents hit head-on, crinkling up the land into a high mountain chain.

  13. Himalayas

  14. Continental-Oceanic (Subduction) • Oceanic lithosphere subducts underneath the continental lithosphere • Oceanic lithosphere heats up and melts, then rises, causing volcanism • E.g. The Andes

  15. Ocean-Ocean Plate Collision • When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. • The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. • The worlds deepest parts of the ocean are found along trenches. • E.g. The Mariana Trench is 11 km deep!

  16. Transform Boundaries • Where plates slide past each other Above: View of the San Andreas transform fault

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