1 / 18

How The P lates M ove

Sea Floor spreading and Subduction. How The P lates M ove. Sea floor spreading. The process by which new ocean lithosphere is created as the older rock material is pulled away. Sea floor Spreading …. Takes place where plate edges meet. M ost often underneath the ocean

dayo
Download Presentation

How The P lates M ove

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sea Floor spreading and Subduction How The Plates Move

  2. Sea floor spreading • The process by which new ocean lithosphere is created as the older rock material is pulled away.

  3. Sea floor Spreading … • Takes place where plate edges meet. Most often underneath the ocean • Molten rock (magma) spurts up between the plates. • As the magma is cooled by the ocean water it forms new crust. • This new crust creates ocean ridges

  4. Sea Floor spreading • This process keeps repeating so new crust is constantly being formed • The crust increases in age the further it is from the ocean ridge

  5. What is our evidence that the crust at the ridges is the youngest?

  6. Magma contains magnetic minerals • These magnetic minerals align with the magnetic field of the Earth – they move toward the north pole

  7. Magnetic Reversals • The (magnetic)North and South pole have switched places many times in Earth’s history • Switching places is called “magnetic reversal” • So the magnetic minerals have created bands or stripes in the crust

  8. How the sea floor spreads -Ridge Push • Two plates come apart in the ocean • Magma rises to fill in the gap and when it cools it forms a ridge (extra rock crust) • The extra weight of the ridge (extra rock crust) puts pressure on the asthenosphere causing magma to rise again

  9. Sea floor spreading features • Rift – is the area of separating plates • Rift valley – is the valley that forms between the ridges • Ridge - is the mountain that is formed by the build up of cooled magma

  10. http://app.discoveryeducation.com/search?Ntt=sea+floor+spreadinghttp://app.discoveryeducation.com/search?Ntt=sea+floor+spreading

  11. Sea Floor Spreading Activity

  12. So does the Earth keep getting bigger?

  13. No! The Earth recycles itself in a process called Slab pull – or SUBDUCTION • As the ridges push out new crust the old crust is pulled back down into the mantle. • A slab pull is when the plates are pulled down into the mantle.

  14. How Subduction works

  15. At the Mid Atlantic Ridge the plates are pulling apart, at the Nazca and S. American plate the plates are colliding and subducting

  16. What forms when subduction occurs?

  17. Trenches and sometimes volcanoes • Trench – is a ditch like feature formed by subduction • Composite Volcanoes

  18. Picture Citations • http://www.pmel.noaa.gov/vents/nemo/education/images/seafloor_spreading.jpg • http://www.womenoceanographers.org/Content/Profiles/MelanieSummit/images/LearnMore1.jpg • http://www.pmel.noaa.gov/vents/nemo/education/images/seafloor_spreading.jpg • http://www.answersingenesis.org/assets/images/articles/am/v2/n2/figure-2-c.jpg

More Related