1. Plate Tectonics Liz LaRosa for use with my 5 th Grade Science Class http://www.middleschoolscience.com 2009 http://www.middleschoolscience.com

2. Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

3. The Crust Outermost layer 5 – 100 km thick Made of Oxygen, Silicon, Aluminum

4. The Mantle Layer of Earth between the crust and the core Contains most of the Earth’s mass Has more magnesium and less aluminum and silicon than the crust Is denser than the crust

5. The Core Below the mantle and to the center of the Earth Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

6. Tectonic Plates

7. Plate Tectonics The theory of the formation and movement of the plates that cover the Earth’s surface The earth is constantly changing. In addition to the effects of weathering and erosion, there are much larger scale changes occurring due to the movement of large plates in the lithosphere. Each plate has a name and fit together like jigsaw puzzles. They float on top of the mantle similar to ice cubes in a bowl of water In the 1930’s, Alfred Wegener proposed the idea that continents were drifting. He could not successfully explain the force that could move such massive amounts of material so his theory did not gain acceptance.

8. Acceptance of Wegener’s Theory In the late 1950’s and early 60’s, evidence emerged that suggested convection within the Earth’s asthenosphere could be the driving force behind the movement of the plates. Further investigations have led to wide spread acceptance of the theory of plate tectonics. The interactions of the plate boundaries also help explain the location of volcanoes and earthquakes. This further supports the theory.

9. Continental Drift http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Contin ents.shtml The theory that all continents are fragments of Pangaea now drifting apart is called Continental Drift. Alfred Wegener 1900’s – Continents were once a single land mass that drifted apart. Fossils of the same plants and animals are found on different continents Called this supercontinent Pangea, Greek for “all Earth” 245 Million years ago Split again – Laurasia & Gondwana 180 million years ago

10. Evidence of Pangea

11. Boundaries The plates interact in 3 different ways called boundaries. The 3 types of boundaries are –transform –convergent and –divergent

12. Different Types of Boundaries http://pubs.usgs.gov/gip/dynamic/understanding.html

13. Convergent Boundaries At convergent boundaries the plates are crashing into each other. If both plates are the same (oceanic/oceanic or continental/continental) they push each other upward in a process called uplift. If the plates are different (oceanic/continental) the oceanic plate gets pushed beneath the continental plate. As the oceanic plate gets pushed deeper into the earth, the oceanic plate melts and the hot magma rises to the surface forming a chain of volcanic mountains.

14. Convergent Boundary – Indian and Eurasian Plates

15. Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.htmlhttp://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.comhttp://www.geology.com

16. Convergent Boundaries - Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.comhttp://www.geology.com

17. Convergent Boundary – Oceanic & Oceanic http://pubs.usgs.gov/gip/dynamic/understanding.htmlhttp://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.comhttp://www.geology.com

18. Divergent Boundaries Plates that are moving apart from each other are called divergent. When continental plates separate, land subsidence occurs. –Subsidence is the motion the Earth's surface as it shifts downward relative to sea-level. When oceanic crust moves apart, magma rises to fill the space creating new oceanic crust.

19. Divergent Boundary – Arabian and African Plates

20. Divergent Boundary – Iceland http://pubs.usgs.gov/gip/dynamic/understanding.html

21. Divergent Boundary - Oceanic http://www.geology.com

22. Divergent Boundary - Continental http://www.geology.com

23. Transform Boundaries Transform boundaries happen when two plates are sideswiping each other (in very slow motion). Major earthquakes occur as these boundaries slip past each other. The plates may be stuck for years, then suddenly break free and move several inches or even feet.

24. Transform Boundary – San Andreas Fault www.geology.com

25. Review Name the 3 main layers of the Earth. –Crust, Mantle, Core What is a tectonic plate? –Piece of the lithosphere that moves around. What was Pangea? –A supercontinent from about 245 million years ago. Name the three different types of plate boundaries and one location on Earth for each one –Convergent = Eurasian and Indian Plates –Divergent = Arabian and African Plates –Transform = San Andres Fault