1. PLATE BOUNDARIES Day 1

2. A. Geographic Puzzle 1. Alfred Wegener - a scientist that first believed that the continents fit together like a puzzle a) Ex: Africa & South America 2. He believed that the continents were once together then moved apart.

3. B. Pangaea 1. Wegener said that 225 mya all the continents were together to form a supercontinent called Pangaea

4. C. Wegener’s Evidence 1. Fossil remains found across continents a) Fossils Ex: Cynognathus & Glossopteris 2. Mountain ranges & coal deposits run unbroken across the continents.

5. D. Continental Drift 1. Wegener believed that the continents (crust) floats on the upper mantle. 2. Continental Drift – The continents are moving away or coming towards one another.

6. Wegener’s matching of mountain ranges on different continents

7. E. PLATES 1. The lithosphere is broken into of many different sized pieces called plates.

8. F. Mid-Atlantic Ridge (MAR) F. Mid-Atlantic Ridge (MAR) 1. MAR – a giant undersea mountain range extending north to south in the center of the Atlantic Ocean 2. The youngest rock is found at the ridge and the age of the rock get older as you move away from the ridge. 3. MAR is evidence of sea- floor spreading (moving apart)

9. Ocean Floor Has Mountain Ranges larger than those found on the surface

10. G. Sea-Floor Spreading 1. Sea-Floor Spreading – (Hess) that new ocean crust is formed at mid-ocean ridges.

11. H. Paleomagnetism 1. The earth’s magnetic field has reversed many times over geologic time. 2. A record of these reversals are placed in the rock as it is formed at the mid-ocean ridges. Magnetic Stripes

13. 3. In 1963 an interpretation of these stripes was developed: a. Earth’s magnetic field changes few hundred thousand years. b. During a reversal, a compass points south, also causing the iron-bearing minerals in newly forming rocks to point south

14. I. Plate Tectonics 1. Evidence from fossils 2. Seafloor spreading & Continental Drift 3. Paleomagnetism – Geomagnetic time scale 4. The movements of these plates causes earthquakes, volcanoes, & mountain building

16. J. Divergent Boundary 1.Divergent Boundary – plates are moving away from one another a)As known as a rift or ridge 2.Forms new crust

17. K. Transform Boundary 1.Transform Boundary – plates are moving side to side (pass one another) 2.Crust is not created or destroyed 3.Ex: San Andreas

18. L. Convergent Boundary 1.Convergent Boundary – plates are moving towards one another a.Plates are colliding b.Also known as trenches or subduction zones 2.Oceanic Crust is destroyed

19. M. Subduction Zone 1.Ocean crust is pushed under the continental crust because ocean crust is denser (high density) than continental crust. a)Oceanic Crust - 3.0 g/cm 3 b)Continental Crust – 2.7 g/cm 3 2.The oceanic crust melt (subduction zone – convergent PB)  becomes magma  rises and volcanoes form (mid-ocean ridge – divergent PB)

20. N. HOT SPOTS 1. Weak areas within a plate where magma may rise. 2. Volcanoes can form in these areas. 3. Can result in a chain of volcanic islands. 4. Ex: Yellowstone National Park & Hawaii

21. Observe an animation of volcanic islands forming over a hot spot.

23. 5. There are over 100 hot spots.