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Theory of _________________

Theory of _________________. Plate Tectonics. Wegener’s Continental Drift Theory. The continents were not always where they are today but rather have drifted apart over millions of years. Evidence. Evidence for Continental Drift Theory includes: Jigsaw puzzle fit of continent,

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Theory of _________________

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  1. Theory of _________________ Plate Tectonics

  2. Wegener’s Continental Drift Theory • The continents were not always where they are today but rather have drifted apart over millions of years

  3. Evidence • Evidence for Continental Drift Theory includes: • Jigsaw puzzle fit of continent, • Geological structures • Fossils • Climatic evidence • BUT...Wegner was ridiculed • How could entire continents move?

  4. More Evidence • In 1915 there was not enough Scientific Evidence for people to believe Wegner’s Theory of Continental Drift • In order for Wegner’s hypothesis to become a theory, he needed to be able to explain HOW or WHAT could make the continents move

  5. Today’s Objectives • Be able to define tectonic plates • Be able to list and discuss evidence for tectonic plate movement • Sea Floor Spreading • Hot Spots • Be able to state the Plate Tectonic Theory • be able to explain how the Plate Tectonic Theory helped to silence Wegener’s critics

  6. Plate Tectonics • In Wegner’s time, scientists did not know that Earth’s surface was broken up into large, moveable slabs of rock • These slabs are called TECTONIC PLATES

  7. Plate Tectonics • These rigid, solid plates float on top of a layer of molten rock • The movement of these plates result in the movement of the continents

  8. How do we know the Plates are Moving? There are 4 main pieces of evidence: • Existence and patterns of Earthquakes and Volcanoes • Existence of ocean ridges • Paleomagnetism, the existence of magnetic striping • Existence of volcanic island chains

  9. #1: Earthquakes and Volcanoes • occur at plate boundaries (the edges of plates) • appear to occur when adjacent plates collide • stationary objects can not collide • suggests that plates must be moving!!!

  10. #2: Ocean Ridges • These are under water mountain ranges • A well known example is the MID-ATLANTIC RIDGE which runs north to south down the entire length of the Atlantic Ocean.

  11. Proof??? • Can be best explained as a formation made by two plates moving AWAY from one another • As the plates move apart, they form a gap • The hot magma rises through the gap, cools and forms new rocks/mountains

  12. Ocean Ridges

  13. Paleomagnetism • This is the study of the magnetic properties of ancient rocks • Like Earth itself, its magnetic field is continually changing • In the last 10 million years the poles have shifted 4-5 times per million years!

  14. #3- Magnetic Striping • Scientists have discovered that Iron grains in rocks align with the magnetic poles • They call this pattern MAGNETIC STRIPPING • Stripes of rock at the bottom of the ocean that have alternating magnetic patterns

  15. More on Magnetic Striping • Can be explained if the plates are moving apart as the Earth’s magnetic field is reversing oldest rock youngest rock 2nd youngest rock older rock

  16. Seafloor Spreading • Ocean ridges and magnetic striping both suggest that the sea floor is spreading or moving • In other words “the plates” are moving

  17. #4- Volcanic Island Chains • Are chains of islands that are formed when magma reaches the Earth’s surface and cools

  18. HOT SPOTS • hotspots = an area where molten rock rises through the Earth’s surface, cools and forms new rock • Volcanic Island Chains can be explained by Hot Spots • Hot spots are stationary spots located BELOW the tectonic plates • Hot Spots do not move, rather the plates move over the hot spots!

  19. As the plates moves, the islands move as well. • As a new portion of the plate moves over the hot spot a new island forms until eventually you get a chain of islands

  20. For example, the Hawaiian Islands • They formed when the Pacific Plate moves North East over a hot spot

  21. typically the smaller islands = the older island • Why??? • As time goes by the islands get eroded away by the ocean water

  22. Plate Direction • Not only does the existence of Volcanic chains and hot spots prove that plates are moving... • They can show the DIRECTION of plate movement!

  23. DIRECTION 1-Oldest 2 3 4- Youngest

  24. Summary of Evidence that Prove that Plates can MOVE • Earthquakes and Volcanoes = occur as plates move and collide • Ocean Ridges = form as plates move apart • Magnetic Stripes = form as plates move apart • Island Chains = form as plates move over hot spots

  25. The Theory of Plate Tectonics • Is a unified theory that came out of the above evidence • States that the Earth’s surface is made up of large plates of rock that float and continually move on top of a molten layer. • Came about after Wegener’s Continental Drift Theory • Supported Wegener’s theory as it explained how continents could move Finally his critics could be Silenced!

  26. PLATE FACTS • There are 7 major plates and 5 minor plates – 12 plates total. • It is on the edgesof the plates – near the borders of plates where all the action is! (earthquakes, volcanoes, mountain building!) • These tectonic plates move approximately 1 inch per year due to CONTINENTAL DRIFT!!! • That is the same rate as your fingernails grow!!!

  27. What makes the plates move? • We know that the continents drift • We know that they sit of rock slabs called Tectonic Plates • BUT, what makes the plates move and how does it work...

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