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The Ocean Floor

The Ocean Floor. I. New Technology. New technology = new information. New information = new ideas & theories. http://www.audiblox2000.com/images/brain_scratching_head.gif. I. New Technology. Echo-Sounding : SoNAR: So und N avigation A nd R anging

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The Ocean Floor

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  1. The Ocean Floor

  2. I. New Technology • New technology = new information. • New information = new ideas & theories http://www.audiblox2000.com/images/brain_scratching_head.gif

  3. I. New Technology • Echo-Sounding: • SoNAR: Sound Navigation And Ranging • Became common on warships during World War II • Used by scientists to make maps of the ocean floor.

  4. I. New Technology http://www.lowrance.com/images/Tutorials/Sonar/sonar2.gif

  5. II. Ocean Floor Topography • It was assumed the ocean floor was flat. • It wasn’t: • huge underwater mountain ridges and valleys

  6. II. Ocean Floor Topography • Mid-Ocean Ridges • underwater mountains that are thousands of miles long. • Located in the center of the oceans • Volcanoes and earthquakes are very common along the ridges. http://www.log.furg.br/WEBens/ocean/wormuth/marineprovinces/natlanticseafloor.gif

  7. II. Ocean Floor Topography • Deep-Sea Trenches • huge underwater valleys up to 7 miles deep. • Found along the edges of many oceans. • Earthquakes are very common near deep-sea trenches.

  8. III. The Oceanic Crust • Scientists took samples of rocks from the ocean floor. • Age of the oceanic crust • Closer to mid-ocean ridges = younger. • Further from a ridge the older the rocks.

  9. III. The Oceanic Crust • Age of the oceanic crust vs. age of continental crust • Oldest Oceanic Rocks: 180 million years old • Oldest Continental Rocks: 3,800 million years old

  10. A new type of self-propelled magnetometer. http://oceanexplorer.noaa.gov/explorations/02fire/background/rovs_auvs/abe_220.jpg IV. Another New Technology • Magnetometer- measures small changes in magnetic fields. • First used in the oceans during the 1950’s.

  11. A new type of self-propelled magnetometer. http://oceanexplorer.noaa.gov/explorations/02fire/background/rovs_auvs/abe_220.jpg IV. Another New Technology • Magnetometers measured the magnetic field of the ocean floor.

  12. V. The Earth’s Magnetic Field • paleomagnetism • the study of Earth’s magnetic field throughout history. • Magnetic Reversals • Every 10,000 years or so: • The north & south magnetic poles switch places.

  13. http://anthro.palomar.edu/time/images/magnetic_north_pole.gifhttp://anthro.palomar.edu/time/images/magnetic_north_pole.gif

  14. V. The Earth’s Magnetic Field • What the magnetometers found: • Symmetric magnetic stripes around ridges! • The stripes had normal and reversed magnetic fields. • Each stripe was formed when the magnetic pole shifted.

  15. V. The Earth’s Magnetic Field Image from: http://www.indiana.edu/~geol116/week7/magstrip.jpg

  16. V. The Earth’s Magnetic Field • A-Ha! • New crust is created at oceanic ridges!

  17. VI. Seafloor Spreading • Harry Hess (1906 – 1969) • He proposed the theory of seafloor spreading. • Seafloor Spreading • New crust is being created at the mid-ocean ridges. • Old crust is destroyed at the oceanic trenches.

  18. VI. Seafloor Spreading • Crust pulls apart • Magma rises up and fills the gap left when the crust pulled apart • The magma hardens, creating new oceanic crust

  19. Eureka!! • Seafloor spreading explains HOW the continents move. • Solves one problem people originally brought up about Alfred Wegener’s theory of continental drift!

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