1. Tectonic Plates

2. Pangea- A super continent that held all our modern continents.

3. This super continent broke apart and formed modern continents.

4. Similar fossils have been found on Different continents.

5. Remains of warm-weather plants in _______________ areas and glacial deposits in__________________ areas suggest that continents have moved.

6. At first, continental drift was not accepted because no one could explain ____________ or __________continents had moved. Alfred Wegener proposed the hypothesis of continental drift in 1911 Wegener's Idea Alfred Wegener proposed the hypothesis of continental drift in 1911 Wegener's Idea

7. Using ______________ waves, scientists discovered a system of underwater mountain ranges called the mid-ocean ridges in many oceans.

8. Ocean Ridges Courtesy of www.ngdc.noaa.gov

9. In the 1960s, Harry Hess suggested the theory of ______ __________ to explain the ridges.

10. Hot, less dense material below Earth’s ______________ rises upward to the surface at the mid-ocean ridges. Then, it flows sideways, carrying the _______________ away from the ridge. As the seafloor spreads apart, ______________ moves up and flows from the cracks, cools, and forms new seafloor. Hot, less dense material below Earth’s ______________ rises upward to the surface at the mid-ocean ridges. Then, it flows sideways, carrying the _______________ away from the ridge. As the seafloor spreads apart, ______________ moves up and flows from the cracks, cools, and forms new seafloor.

11. Evidence for seafloor spreading _________________ rocks are located at mid-ocean ridges.

12. Youngest at ridge Progressively older away from ridge Mirror image across the ridge Youngest at ridge Progressively older away from ridge Mirror image across the ridge Courtesy of www.ngdc.noaa.gov

13. Reversals of Earth’s _________________ field are recorded by rocks in strips parallel to ridges.

14. Plate movements 1.Earth’s ______________ and upper mantle are broken into sections. 2.The sections, called _______________, move on a plasticlike layer of the mantle. 3.The plates and upper mantle form the ____________________. 4.The plasticlike layer below the lithosphere is called the ______________________. 1.Earth’s ______________ and upper mantle are broken into sections. 2.The sections, called _______________, move on a plasticlike layer of the mantle. 3.The plates and upper mantle form the ____________________. 4.The plasticlike layer below the lithosphere is called the ______________________.

15. Plate movements Plates moving ______________—divergent boundaries

16. Iceland Iceland has a divergent plate boundary running through its middle

17. Plates moving _________________ —convergent boundaries a.Denser plates sink under less ______________ plates.

19. b.Newly formed hot ______________ forced upward forms volcanic mountains.

20. Plates collide a.Plates crumple up to form _________________ ranges. b.____________________ are common. a.Plates crumple up to form _________________ ranges. b.____________________ are common.

21. Plates slide past—called __________________ boundaries; sudden movement can cause earthquakes

22. Convection inside Earth—the cycle of heating, rising, cooling, and sinking of material insideEarth is thought to be the ______________ behind plate tectonics.

23. Features caused by plate tectonics 1.Faults and _____________ valleys 2.Mountains and ___________________ 3.Strike-slip faults—cause of ____________________ 1.Faults and _____________ valleys 2.Mountains and ___________________ 3.Strike-slip faults—cause of ____________________

24. Testing for plate tectonics—scientists can measure __________________ as little as 1 cm per year.