1. The Structure of the Earth and Plate Tectonics

2. Structure of the Earth The Earth is made up of 3 main layers: –Core –Mantle –Crust Inner core Outer core Mantle Crust

3. The Crust This is where we live! The Earth’s crust is made of: Continental Crust - thick (10-70km) - buoyant (less dense than oceanic crust) - mostly old Oceanic Crust - thin (~7 km) - dense (sinks under continental crust) - young

4. Pangaea If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle. Fossils of the same animal were found on two different continents (Africa and S. America). This suggested that the plates were once all together. History of Plate Tectonics

5. Convection currents cause plate movement resulting in seafloor spreading (continents move apart) –Convection: a circular current where Earth’s heated material rises and cooler material sinks. Why Plates Move

6. What is Plate Tectonics?

7. Plate Tectonics The Earth’s crust is divided into 12 major plates which are moved in various directions. This plate motion causes them to collide, pull apart, or scrape against each other. Each type of interaction causes a characteristic set of Earth structures or “tectonic” features. The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.

8. World Plates **They are named based on their location, usually after the continent**

9. What happens at tectonic plate boundaries?

10. We are going to learn about the three types of plate boundary

11. Where plates slide past each other Transform Boundaries Transform boundaries are marked in some places by linear valleys along the boundary where rock has been ground up by the sliding. In other places, transform boundaries are marked by features like stream beds that have been split in half and the two halves have moved in opposite directions.

12. Transform Boundaries Perhaps the most famous transform boundary in the world is the San Andreas fault, shown in the drawing to the left. The slice of California to the west of the fault is slowly moving north relative to the rest of California. Since motion along the fault is sideways and not vertical, Los Angeles will not crack off and fall into the ocean as popularly thought, but it will simply creep towards San Francisco at about 6 centimeters per year. In about ten million years, the two cities will be side by side! Although transform boundaries are not marked by spectacular surface features, their sliding motion causes lots of earthquakes.

13. Plates move apart from one another Think dividing = divergent Divergent Boundaries in the ocean

14. Divergent Boundaries in the ocean Courtesy of www.ngdc.noaa.gov As plates move apart new material is erupted to fill the gap, this creates a mid-ocean ridge. At divergent boundaries, new crust is created as two or more plates pull away from each other, this is known as sea-floor spreading. When a diverging boundary occurs on land a 'rift', or separation will arise and over time that mass of land will break apart into distinct land masses and the surrounding water will fill the space between them. The move is very slow, for example the Mid-ocean ridge widens only 2 centimeters per year

15. Divergent Boundaries on land When a diverging boundary occurs on land a 'rift', or separation will arise and over time that mass of land will break apart into distinct land masses and the surrounding water or other material will fill the space between them

16. Earthquakes occur along the faults, and volcanoes form where the magma reaches the surface. Divergent Boundaries on land

17. Iceland: An example of continental rifting Iceland offers scientists a natural laboratory for studying - on land - the processes that occur along a divergent boundary. Iceland is splitting along the Mid- Atlantic Ridge - a divergent boundary between the North American and Eurasian Plates. As North America moves westward and Eurasia eastward, new crust is created on both sides of the diverging boundary. While the creation of new crust adds mass to Iceland on both sides of the boundary, it also creates a rift along the boundary. Iceland will inevitably break apart into two separate land masses at some point in the future, as the Atlantic waters eventually rush in to fill the widening and deepening space between.

18. There are two styles of convergent plate boundaries –Similar Density: when 2 plates with similar densities collide such as continent-continent collision. –Different Density: when 2 plates with different densities collide such as ocean- ocean collision or continent-ocean collision Convergent Boundaries 2 plates “crash” into each other

19. Two different plates collide (crash) The land is pushed up to form mountains, e.g. European Alps, Himalayas Convergent Boundaries – Similar Density: Continent-Continent Collision

20. Himalayas

21. Called SUBDUCTION (sinks) As one plate sinks below the other a trench is formed. The sunken plate is heated by the Earth and a volcano is formed. This also forms the Ring of Fire Convergent Boundaries with different density:

22. Volcanism is mostly focused at plate margins Pacific Ring of Fire

23. 1. Ocean-Ocean Plate Collision When two oceanic plates collide, one runs over the other which causes it to sink into the mantle. The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. The worlds deepest parts of the ocean are found along trenches. –E.g. The Mariana Trench is 11 km deep! Two types of divergent with different densities:

24. 1. Ocean-Continent Plate Collision When an oceanic plate pushes into and subducts under a continental plate, the overriding continental plate is lifted up and a mountain range that is usually volcanic is created. Two types of divergent with different densities: