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Plate Tectonics
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Plate Tectonics

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Slides on Plate Tectonics for Leaving Certificate Geography (Irish education system).

Slides on Plate Tectonics for Leaving Certificate Geography (Irish education system).

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  • 1. The crust is the thin, outer part of the Earth. It is thickest on land and thinner under the oceans. The crust is divided into a number of sections called tectonic plates that float on the molten mantle below The movement of the plates causes Earthquakes, fold mountains and volcanoes. The plates move because of convection currents in the mantle underneath
  • 2. Oceanic (young) ◦ 6 – 12K thick ◦ Dense heavy rocks (usually basalt) ◦ Silicon and Magnesium rich rocks (SIMA) Continental (older) ◦ 40 – 60 K thick ◦ Lighter rocks (granite, limestone etc) ◦ Silicon and Aluminium rich rocks (SIAL)
  • 3. This is the study of the processes that cause the movement of the Earth’s plates and the landforms that result. Plate Tectonics is a mixing of two theories ◦ Continental Drift by Alfred Wegener ◦ Sea Floor Spreading by Harry Hess
  • 4. Fossils of same animal species on different continents Matching rock types and mountain trends on different continents Matching coastline shape (Africa and S. America)
  • 5. North American Plate Eurasian Plate Newly formed crust
  • 6. Different magnetic patterns on rocks either side of the mid ocean ridges match up Youngest rocks are nearest the mid ocean ridge Youngest islands are nearest the ridge (e.g. Iceland) – older Islands (e.g. Ireland are furthe away)
  • 7. The Earth’s North and South magnetic poles have reversed several times in Earth’s history Grains of iron in lava point toward the magnetic pole as it cools – keeping a record of the magnetic field at the time The ideas of Continental Drift and Sea Floor Spreading were merged in the 1960s to form the Theory of Plate Tectonics by Vine and Matthews
  • 8. SIAL How plates move Basalt Mantle-Crust boundary Harry Hess Fold Mountains Convection Constructive plate boundary Fossils Silicon-Aluminium Pangaea Proof of continental drift Granite Oceanic Plate Rock Moho Sea Floor Spreading Mid Atlantic Ridge Continental Plate Rock Himalayas One big “Super Continent”
  • 9. Oceanic – Continental plate collisions form... ◦ trenches ◦ Earthquakes ◦ Fold mountains and volcanoes ◦ Terranes (piles of sedimentary material at plate boundaries) Key Term: Subduction (one plate pushed under another) Volcanic eruptions at these boundaries are often very violent
  • 10. Trench Fold Mountains (Andes)
  • 11. Oceanic – Oceanic plate collisions form... ◦ Trenches ◦ Island Arcs – lines of volcanic islands (e.g. Japan and its islands) ◦ Earthquakes

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