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T ECTONIC P LATES

T ECTONIC P LATES. Last Day Wegener’s Continental Drift Theory the continents were not always where they are today but rather have drifted apart over millions of years. Last Day Evidence for Continental Drift Theory includes: jigsaw puzzle fit of continent, geological structures

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T ECTONIC P LATES

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  1. TECTONIC PLATES

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

  3. Last Day • Evidence for Continental Drift Theory includes: • jigsaw puzzle fit of continent, • geological structures • fossils • climatic evidence • Wegner was ridiculed • How could entire continents move?

  4. Today’s Goals  be able to define tectonic plates  be able to list and discuss evidence for tectonic plate movement • existence and patterns of Earthquakes and Volcanoes • existence of ocean ridges • existence of magnetic striping • existence of volcanic island chains • be able to state the Plate Tectonic Theory • be able to explain how the Plate Tectonic Theory helped to silence Wegener’s critics

  5. What are Tectonic Plates? • =massive chunks of rock that form the Earth’s surface • the plates float and move on the Earth’s molten core

  6. How can we tell tectonic plates move? • several pieces of evidence including: • existence and patterns of Earthquakes and Volcanoes • existence of ocean ridges • existence of magnetic striping – (Paleomagnetism) • existence of volcanic island chains

  7. Earthquakes and Volcanoes • occur at plate boundaries (the edges of plates) • appear to occur when adjacent plates collide • stationary objects cannot collide!!! • suggests that plates must be moving

  8. Ocean Ridges • = underwater mountain ranges • example = Mid-Atlantic Ridge

  9. Ocean Ridges • can be explained if the plates at the bottom of the ocean are moving apart • as plates move apart, a gap forms in the Earth’s crust • magma then rises through the gap, cools and forms new rocks andmountains • Rock near the ridge is young/new rock and thin. Rock far away from the ridge is old and thick. • Ridge in Iceland

  10. What is Magnetic Striping? – Paleomagnetism • stripes of rock at the bottom of the ocean that have alternating magnetic patterns

  11. Why does magnetic striping happen?

  12. Earth is like a large bar magnet. It has a north pole and a south pole. • A compass needle points to the north.

  13. Over 1 million years, Earth’s magnetic poles reverse four or five times. • During magnetic reversal, a compass needle would point south.

  14. 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

  15. Sea floor spreading • ocean ridges and magnetic striping both suggest that the sea floor is spreading or moving apart • in other words “the plates” are moving

  16. Volcanic Island Chains • are chains of islands that are formed when magma reaches the Earth’s surface and cools

  17. Volcanic Island Chains • can be explained if plates move over hotspots • hotspots = an area where molten rock rises through the Earth’s surface, cools and forms new rock • hotspots are stationary in the Earth’s molten core • as the plate moves, the islands move • as a new portion of the plate moves over the hotspot, a new island forms until eventually you get a chain of islands

  18. For example, the Hawaiian Islands • form as the Pacific Plate moves North East over a hot spot

  19. For example, the Hawaiian Islands • typically the smaller islands = the older island because the island has been eroded away over time by the ocean and weather

  20. Summary of evidence that suggests 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 and Earth reverses polarity • Island Chains = form as plates move over hot spots

  21. Plate Tectonic Theory • is a unified theory that came out of the above evidence • states that the Earth’s surface is made up of large plates of rocks that float and continually move on top of Earth’s molten core • came about afterWegener’s Continental Drift Theory • supported Wegener’s theory as it explained how continents could move • finally silenced his critics because he now had evidence to suggest that the continents were once together in a supercontinent (jigsaw puzzle fit of continents, fossils, geological structures, paleoglaciation and coal deposits) and evidence to support/explain how continents could drift (plate tectonics)

  22. Homework • In your textbook Read p. 207 – 209 • Workbook 12.1

  23. Homework • In your textbook Read p. 207 – 209 • Workbook 12.1 • Vocabulary Book • Bonus Homework - Get a Student of the Week Ticket Do textbook questions on p. 212 – 213

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