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Geology Rocks!

Geology Rocks!. A meeting of plates “The Great Rift”. 6th Science Std: 1. We have covered…. The layers of the earth…. We have covered…. The layers of the earth…. We have covered…. Measuring the Plate’s Motion…. Using GPS Satellites . And very good GPS receivers.

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Geology Rocks!

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  1. Geology Rocks! A meeting of plates “The Great Rift” 6th Science Std: 1

  2. We have covered….. The layers of the earth…..

  3. We have covered….. The layers of the earth…..

  4. We have covered….. Measuring the Plate’s Motion…. Using GPS Satellites And very good GPS receivers We measure the direction and speed of plates….

  5. We have covered….. Plate Tectonic theory…… Where it came from How it became a theory And where the plates are…..

  6. So now, let’s look at….. What happens when plates meet plates

  7. Three types of plate boundaries: 1. Divergent Plate Boundaries where new crust is created as the plates pull away from each other

  8. Three types of plate boundaries: 2. Convergent Plate Boundaries where crust is destroyed as one plate dives under another

  9. Three types of plate boundaries: 3. Transform Plate Boundaries where crust isn’t created or destroyed as the plates slide horizontally past each other

  10. Three types of plate boundaries: These boundaries are all over the earth…..

  11. Divergent Boundaries….. Divergent boundaries occur along spreading centers Where plates are moving apart And new crust is created by magma pushing up from the mantle

  12. Divergent Boundaries….. Picture two giant conveyor belts…. …..moving in opposite directions

  13. Divergent Boundaries….. New material is brought up through the middle….. Making new crust where it is spreading……. As much as 2 to 3 cm per year…..

  14. Divergent Boundaries….. Where is this happening? Underwater, we call it a Mid Ocean Ridge There is one in the middle of the Atlantic Ocean It goes from north of Iceland to south of Africa

  15. Divergent Boundaries….. Where is this happening? On the land we call it a Rift Valley The best known is in Central Africa It is splitting Africa apart at the dotted line

  16. Divergent Boundaries….. Magma from the Asthenosphere pushes up the Lithosphere How does this work? Sometimes magma makes volcanoes Sometimes it just makes the ground split apart and spread

  17. A rift valley near Quilotoa, Ecuador. Divergent Boundaries….. How does this work? A rift valley is formed when…. …the magma dome under the lithosphere…. …drops back down into the mantle

  18. Divergent Boundaries….. How do we know this is really happening? If new sea floor is made so slowly… How do we know?

  19. Divergent Boundaries….. What drives this motion Thermal Convection But what is that?

  20. Divergent Boundaries….. The heat in the core isn’t the same everywhere Hot Cold Cold There are some “hot spots” And some “cold spots”

  21. Divergent Boundaries….. The heat in the core isn’t the same everywhere Hot Cold Cold And falls at the “cold spots” Heat rises at the “hot spots”

  22. Divergent Boundaries….. This is the “motor” for the Earth’s ‘conveyor belt’ Hot Cold Cold Magma rises, moves under the lithosphere pushing it

  23. Divergent Boundaries….. Two Different Ways: Age of the Rocks on the Sea Floor And Paleomagnetism

  24. Age of Rocks Rocks are “born” when they cool from magma After they are born, they are put on the plate “conveyor belt” The belt moves the rock away from the rift / ridge As the rock slowly moves, it gets older

  25. Age of Rocks The “Conveyor” keeps moving with the rock The farther it goes, the older the rock gets….. So it gets older and older the farther it goes…. So a trend was noticed……….

  26. Age of Rocks Rocks near the ridge/rift were new Rock farther away were older The rocks can’t move by themselves…… So the ground must be moving

  27. Paleomagnetism The study of the Earth’s Magnetic field preserved in magnetic minerals over time When a rock is “born” it gets slightly magnetized The magnets in the rocks point the same direction as the Earth’s magnetic field And show the direction and strength of the field

  28. Paleomagnetism But the Earth’s magnetic field changes slowly over time….. N The North Pole is now where magnetic north is But a long time ago, the magnetic poles were backwards…. This was called a “reverse magnetic pattern” S

  29. New crust is made of iron rich rock called Basalt

  30. This pattern of dark and light areas is called “Zebra Striping”

  31. Check what you know…. Can you answer the following questions… The lithospheric plates are moving because the magma is moving under it. Why is the magma moving under the lithosphere – explain in detail. Scientists use 2 pieces of evidence to support the theory of plate tectonics – specifically that sea floor spreading was happening. What are these pieces of evidence and explain how each shows sea floor spreading.

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