Earthquakes, Volcanoes & The Ring of Fire

1. Convection in Earth’s Mantle—heat from Earth’s core and the mantle itself cause convection currents in the mantle. 1. Convection in Earth’s Mantle—heat from Earth’s core and the mantle itself cause convection currents in the mantle. 2.Continental Drift: Wegener’s idea that the continents slowly moved over Earth’s surface. 2.Continental Drift: Wegener’s idea that the continents slowly moved over Earth’s surface.

3. Wegener’s hypothesis was that all the continents had once been joined together (Pangaea) and has since drifted apart. 3. Wegener’s hypothesis was that all the continents had once been joined together (Pangaea) and has since drifted apart. His hypothesis was originally rejected by scientists, and now it is believed he was correct. His hypothesis was originally rejected by scientists, and now it is believed he was correct. Continental Drift Animation

He believed this based on 3 types of evidence: He believed this based on 3 types of evidence: a. Evidence from Landforms b. Evidence from Fossils c. Evidence from Climate

4. Mid-Ocean Ridge—the longest chain of mountains in the world; curves like the seam of a baseball along the sea floor, extending into all of Earth’s oceans. 4. Mid-Ocean Ridge—the longest chain of mountains in the world; curves like the seam of a baseball along the sea floor, extending into all of Earth’s oceans. Q: How did scientists map the mid-ocean ridge? sonar Q: How did scientists map the mid-ocean ridge? sonar

5. At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge. 5. At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge. 6. Sea-floor Spreading: the process that continually adds new material to the ocean floor 6. Sea-floor Spreading: the process that continually adds new material to the ocean floor Sea-Floor Spreading Animation

7. There are 3 types of evidence of sea-floor spreading: 7. There are 3 types of evidence of sea-floor spreading: a. molten material near the mid-ocean ridge had a strange shape, like pillows, which can only form when molten material cools a. molten material near the mid-ocean ridge had a strange shape, like pillows, which can only form when molten material cools b. magnetic stripes b. magnetic stripes c. drilling samples from the ocean floor found that samples of rocks nearest the mid-ocean ridge were younger than the samples of rock that were farther away c. drilling samples from the ocean floor found that samples of rocks nearest the mid-ocean ridge were younger than the samples of rock that were farther away

8. At deep-ocean trenches, subduction allows part of the ocean floor to sink back into the mantle. 8. At deep-ocean trenches, subduction allows part of the ocean floor to sink back into the mantle. 9. The Theory of Plate Tectonics —explains the formation, movement, and subduction of Earth’s plates. The plates move only one to ten cm per year. 9. The Theory of Plate Tectonics —explains the formation, movement, and subduction of Earth’s plates. The plates move only one to ten cm per year.

10.Plate Boundaries (illustrate each of the following) a. Transform Boundaries a. Transform Boundaries b. Divergent Boundaries b. Divergent Boundaries c. Convergent Boundaries c. Convergent Boundaries d. Collisional Boundaries d. Collisional Boundaries

11. Plate movement can alter Earth systems and produce changes in Earth’s surface such as faulting, earthquakes, volcanoes, rift valleys, mountain building, trenches and volcanoes- just to name a few! 11. Plate movement can alter Earth systems and produce changes in Earth’s surface such as faulting, earthquakes, volcanoes, rift valleys, mountain building, trenches and volcanoes- just to name a few!

12. Faults usually occur along plate boundaries. 12. Faults usually occur along plate boundaries. 13. Earthquakes- Movement along a fault releases strain energy. When this potential energy is released, it moves outward from the fault in the form of seismic waves. 13. Earthquakes- Movement along a fault releases strain energy. When this potential energy is released, it moves outward from the fault in the form of seismic waves.

14. The focus of an earthquake is the point inside Earth where it starts. The epicenter is the point on Earth’s surface located directly above the focus. Seismic Waves emanate from this point. 14. The focus of an earthquake is the point inside Earth where it starts. The epicenter is the point on Earth’s surface located directly above the focus. Seismic Waves emanate from this point. 15. Most earthquakes occur in well-known belts. About 80% of them occur in the Pacific Ring of Fire- the same belt in which many of Earth’s volcanoes form. 15. Most earthquakes occur in well-known belts. About 80% of them occur in the Pacific Ring of Fire- the same belt in which many of Earth’s volcanoes form. Focus, Epicenter Animation

16. When plates collide, rather than being subducted, the plates pile into each other, causing one or both plates to fold up like an accordion. This process elevates the crust, folds and deforms it heavily, and produces a mountain range. 16. When plates collide, rather than being subducted, the plates pile into each other, causing one or both plates to fold up like an accordion. This process elevates the crust, folds and deforms it heavily, and produces a mountain range.

17. Folding and faulting that is driven by plate movement results in mountain building. 17. Folding and faulting that is driven by plate movement results in mountain building. 18. Rift Valleys occur along divergent boundaries where the plates separate or are moving away from one another. 18. Rift Valleys occur along divergent boundaries where the plates separate or are moving away from one another.

19. Land Subsidence occurs when the land surface sinks as a result of geologic processes or human activities. 19. Land Subsidence occurs when the land surface sinks as a result of geologic processes or human activities. 20. Trenches are deep, linear, relatively narrow depressions in the sea floor, formed by the subduction of oceanic plates (where one plate slides beneath the other). 20. Trenches are deep, linear, relatively narrow depressions in the sea floor, formed by the subduction of oceanic plates (where one plate slides beneath the other).

21. Most volcanoes occur along diverging plate boundaries; most are along the edge of the continents. 21. Most volcanoes occur along diverging plate boundaries; most are along the edge of the continents. Plate Boundaries

22. Volcanoes form 2 ways: 22. Volcanoes form 2 ways: a. One way is when two oceanic plates collide. This can produce a string of volcanic islands like the Caribbean Islands. a. One way is when two oceanic plates collide. This can produce a string of volcanic islands like the Caribbean Islands.

b. The second way volcanoes can form is when an oceanic plate collides with a continental plate. The older and denser oceanic plate subducts, or sinks below the less dense plate. Rock in and above the sinking plate melts, forming chambers of magma that erupt. b. The second way volcanoes can form is when an oceanic plate collides with a continental plate. The older and denser oceanic plate subducts, or sinks below the less dense plate. Rock in and above the sinking plate melts, forming chambers of magma that erupt.