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Explore the captivating history of plate tectonics and continental drift, from Wegener's bold hypothesis to modern geological evidence. Uncover how ancient climates and geological features provide clues to Earth's dynamic past. Witness the puzzle of Pangaea and the gradual dance of continents over millions of years. Discover the fascinating saga of scientific acceptance and rejection, shaping our understanding of the ever-changing Earth.

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Table of Contents

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  1. Table of Contents Title: Chapter 17 Plate Tectonics; 17.1 Drifting Continents Page: 85 Date: 3/11/2013

  2. Objective Students will be able to identify lines of evidence that led Wegener to suggest that Earth’s continents have moved. Students will be able to discuss evidence of ancient climates supported by continental drift. Students will be able to explain why continental drift was not accepted when it was first proposed.

  3. Word of the Day Hypothesis: A testable explanation of a situation.

  4. Drifting Continents • Main Idea: • The shape and geology of the continents suggests that they were once joined together.

  5. Drifting Continents • Early Observations: • First evidence from cartographers (map makers.) • Noticed continents fit together like puzzle pieces. • 1500s Abraham Ortelius (Dutch) proposed that North and South America had been separated from Europe and Africa by earth quakes and floods.

  6. Abraham Ortelius 1858 Continental Puzzle Map

  7. Drifting Continents • Early Observations: • 1912 Alfred Wegener (German) made 1st scientific proposal.

  8. Alfred Wegener (Looks like Mr. Martino)

  9. Drifting Continents • Continental Drift • Wegener’s theory: • Continents were once joined as a single land mass called Pangaea “All Earth.” • Pangaea broke up 200 million years ago. • Continents have been moving ever since.

  10. Pangaea

  11. Drifting Continents • Evidence (3 Pieces) • Evidence from Rock Formations: • Wegener found identical rock layers in Appalachian Mountains, Greenland and Europe - all older than 200 million years.

  12. Rock Layer Evidence of Continental Drift

  13. Drifting Continents • Evidence (3 Pieces) • Evidence from Fossils: • Wegener found fossils of similar land animals and plants on different continents. • No way land animals could have swam across oceans.

  14. Fossil Evidence of Continental Drift

  15. Fossil Evidence of Continental Drift Mesosaurus (An aquatic reptile that Wegener believed was Not able to swim across an entire ocean.)

  16. Drifting Continents • Evidence (3 Pieces) • Climatic Evidence: • Fossil of plant Glassopteris found in South America, Antarctica and India. • Plant only grows in warm climates. • Climates on these continents must have been different - warmer.

  17. Drifting Continents • Evidence (3 Pieces) • Climatic Evidence: • Coal Deposits: • Coal forms from the compaction and decomposition of accumulations of ancient tropical swamp plants. • Coal deposits found in Antarctica. • Antarctica must have had a tropical climate - must have been closer to the equator.

  18. Pangaea Coal Deposits

  19. Drifting Continents • Evidence (3 Pieces) • Climatic Evidence: • Glacial Deposits: • Found 290 million year old glacial deposits in Africa, India, South America and Australia. • Current locations of these continents are too warm for glaciers. • Continents must have once been closer to South Pole.

  20. Evidence from Glacial Deposits

  21. Drifting Continents • A Rejected Notion • 1900s Scientists thought continents had been carved out by erosion and rejected Wegener’s theory of Continental Drift. • 2 Questions Wegener could not explain: • What forces caused continents to move? • How could continents move through solids? • Not until WWII when technology was developed that Wegener’s hypothesis was taken seriously.

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