1. The Layers of the Earth Objectives: 2.1.1  What are the components that makes up the layers of the Earth?  Explain how various mechanisms drive the movement of the lithospheric plates (plate boundaries, ocean trenches, mountain ridges, mid-ocean ridges, plate tectonics, & geologic activities)

2. Warm – Up 9/25 Please use your textbooks and my notes to define the following terms. Use complete sentences. 1.Mantle Convection 2. Plate Tectonics 3. Ridge Push 4. Asthenosphere 5. Lithosphere 6. Seafloor Spreading

3. The Layers of the Earth

4. The Four Layers The Earth is composed of four different layers. The crust is the layer that you live on, and it is the most widely studied and understood. The mantle is much hotter and has the ability to flow. The outer core and inner core are even hotter with pressures so great you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!

5. The Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans (oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust).

6. The Lithospheric Plates The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, semi-rigid asthenosphere.

7. The Asthenosphere The asthenosphere is the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight.

8. The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.

9. The Crust The crust is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this the less dense continents ride on the denser oceanic plates.

10. The Mantle The Mantle is the largest layer of the Earth. The middle mantle is composed of very hot dense rock that flows like asphalt under a heavy weight. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move.

11. Convection Currents The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over.

12. Convection Currents The next time you heat anything like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration. Safety Caution: Don’t get your face too close to the boiling water!

13. The Outer Core The core of the Earth is like a ball of very hot metals. The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron.

14. The Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid.

15. Plate Boundaries 3 Types of Plate Boundaries: Divergent plate boundaries: the two plates move away from each other. Convergent plate boundaries: the two plates move towards each other. Transform/Fault plate boundaries: the two plates slip past each other. Plate boundaries are the edges where two plates meet. Most geologic activity, including volcanoes, earthquakes, and mountain building, takes place at plate boundaries where two enormous pieces of solid lithosphere interact.

16. Plate Boundaries Divergent Boundaries New crust is created, and plates are pull away from each other. Oceans are born and grow wider where plates diverge or pull apart. Convergent Boundaries: When an oceanic plate pushes into and subducts under a continental plate, the overriding continental plate is lifted up and a mountain range is created.

17. Plate Boundaries Convergence Boundaries When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways.

18. Plate Boundaries Convergence Boundaries When two oceanic plates converge one is usually subducted under the other and in the process a deep oceanic trench is formed.

19. Plate Boundaries Transform-Fault Boundaries Two plates are sliding horizontally pass one another. They are also called faults. Most transform faults are found on the ocean floor. They commonly offset active spreading ridges, producing zig-zag plate margins, and are generally defined by shallow earthquakes. A few, however, occur on land.

20. Assignment Please work in groups of twos to complete the assignment. Your work should be turn in at the end of class.