Do Now

1. Do Now • Grab a textbook, turn in progress reports if you have them • Why do we have a magnetic field around our planet? • What does the lithosphere float on top of? • What is the difference between the outter core and the inner core?

2. Objective • SWBAT- describe the theory of continental drift and plate tectonics • Identify the 7 major plates and the 7 minor plates • Identify the three plate boundaries and what feature is associated with each plate boundary

3. TESTING PLATE TECTONICS Sections 9.4 and 9.5

4. Guided Notes • Your task- Use your textbooks to fill out the first column of the guided notes • 233

5. Earth’s Structure • Earth’s interior consists of three major zones defined by its chemical composition: 1. Crust 2. Mantle 3. Core

6. Crust 1. Thin, rocky outer layer of Earth • 2 types: continental and oceanic • Continental crust is about 5-47 miles (very thick) • Consists of many rock types • Oceanic crust is about 4 miles thick (thin) • Composed of igneous rocks

7. Mantle 1. Solid, rocky shell that extends to a depth of about 1800 miles 2. Divided into Upper Mantle & Lower Mantle 3. Largest layer of the Earth

8. Core • Made mostly of iron-nickel alloy • Very hot 3. Inner core • Radius of about 760 miles • Due to the extreme pressure, the material is solid Outer core • Liquid layer is about 1400 miles thick • Earth’s magnetic field is generated from the flow of metallic iron

9. Lithosphere • Crust and upper most part of the mantle • Rigid Asthenosphere • Beneath lithosphere • Soft and flexible

10. Continental Drift Hypothesis • A German scientist and meteorologist, Alfred Wegener, proposed a hypotheses: • Pangaea : The continents had once been joined to form a single supercontinent, • Pangaea meaning all land

11. Evidence for continental drift • The Continental Puzzle • Similar coastlines on opposite sides of the ocean • Continents fit together, like a puzzle • Matching Fossils • Fossil organisms found on different landmasses • Rock Types and Structures • Several mountain belts end at one coastline and reappear on a landmass across the ocean • Appalachian Mountains in US, ending off the coast of Newfoundland (Figure 4 on page 251) • Ancient Climates • Glacier evidence, Figure 5 on page 252

12. Matching Mountain Ranges

13. Glacier Evidence

14. A New Theory Emerges… • Wegener could not provide an explanation of exactly what made the continents move • Data on earthquake activity and Earth’s magnetic field became available • By 1968, these findings led to a new theory, plate tectonics

15. Plate Tectonics Theory • The upper most mantle and crust, behave as a strong, rigid layer known as the lithosphere • Lithosphere is divided into plates, which move and continually change shape and size (move about 5cm per year) • 7 major plates (pages 256-257, Figure 8) • The grinding movements of the plates generate earthquakes, create volcanoes and deform masses of rock into mountains

17. Plate Boundaries • Convergent • Two plates move together • Divergent • Two plates move apart • Transform (fault) • Two plates slide past each other

18. Features Associated with boundaries • Volcanoes- Subduction zones (convergent boundaries) • Mountain ranges – (convergent boundaries) • Sea floor spreading – Ocean Ridge (divergent boundaries) • Earthquakes – (transform)

19. Volcano

20. Mountain range

21. Sea floor spreading

22. Plate tectonics • http://www.youtube.com/watch?v=ryrXAGY1dmE

23. TESTING PLATE TECTONICS • Paleomagnetism • When a rock forms, it becomes magnetized in the direction parallel to Earth’s existing magnetic field • Normal polarity – when rocks show the same magnetism as the present magnetic field • Reverse polarity – when rocks show the opposite magnetism as the present magnetic field

24. EVIDENCE FOR PLATE TECTONICS • The discovery of strips of alternating polarity, which lie as mirror images across ocean ridges, is among the strongest evidence of seafloor spreading

25. Animation • http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_paleomag.html

26. Diagram • Draw a diagram and label • 1) sea floor spreading happening at a mid ocean ridge • 2) Subduction happening between oceaninc and continental crust near a trench • 3) A mountain range along a coastline • ** Label what type of boundary is associated with each feature (transform, convergent, divergent)

27. Exit ticket

28. EVIDENCE FOR PLATE TECTONICS • Earthquake Patterns • Scientists discovered a close link between earthquake origins and ocean trenches • Earthquakes occur only within the subducted slab of oceanic lithosphere • Ocean Drilling • Youngest oceanic crust is at the ridge crest, the oldest crust is at the continental margins • Data on the ages of seafloor sediment confirmed the seafloor spreading hypothesis

29. EVIDENCE FOR PLATE TECTONICS • Hot Spot (Volcanic area) • A concentration of heat in the mantle produces magma, which rises to Earth’s surface creating volcanic mountains • Hot Spot evidence supports the theory that plates move over Earth’s surface Hawaiian Islands

30. Causes of Plate Motion • Convection occurring in the mantle, specifically asthenosphere, is the driving force for plate movement • Convective flow is the motion of matter resulting from changes in temperature • Warm, less dense material rises • Cool, more dense material sinks • The unequal distribution of heat within Earth causes convection in the mantle, which drives plate motion

31. CAUSES OF PLATE MOTION Slab-pull occurs when the cool, dense oceanic crust sinks into the mantle and “pulls” the lithosphere along Ridge-push causes oceanic lithosphere to slide down the sides of the oceanic ridge under the pull of gravity

32. EARTHQUAKES Earthquakes: The shaking of the earth’s crust caused by the release of energy. • focus: point within Earth where the EQ begins • B. epicenter: location on earth’s surface directly above focus • C. faults: 1 cause of EQ’s, large fracture in crust

33. Causes of Earthquakes