Earth’s Structure

1. Earth’s Structure Unit C Chapter 7 Lesson 1 C38 – C45

2. OBJECTIVES • Identify and describe Earth’s layers. • Recognize that Earth’s lithosphere is broken into plates that move slowly across Earth’s surface. • Recognize that the rock record shows Earth’s continents have moved across time.

3. MAIN IDEA • Earth has a layered structure. Its outer layer is made up of moving plates.

4. Vocabulary

5. CORE • Earth’s innermost structure. • Divided into two regions. • Outer core 1,400mi thick and is the only layer in liquid state • Inner core 720mi thick is the hottest layer mad up of iron & nickel, but the pressure keeps the metal from melting

6. CRUST • Thin, nearly solid rock layer that is uppermost in Earth’s structure. • Thinnest layer • Nearly solid rock. • Thickness under the continents is 24miles • Under mountains 42miles • Under ocean-floor about 4mi.

7. LITHOSPHERE • Area where Earth’s solid upper mantle and crust combine to form a rigid shell. • Floats on the mantle

8. MANTLE • Thick layer of Earth’s structure just below Earth’s crust. • 2,900km (1,800mi) thick • Makes up 2/3 of Earth’s mass • Rock material is partially melted

10. PLATE TECTONICS • Idea that giant plates or rock are moving slowly across Earth’s surface

11. Hot Inside • Geysers – hot water shooting up for Earth’s surface. • Water drains deep into Earth’s surface. • How rocks heat up water until steam forms • Pressure forces the remaining water to erupt • Yellowstone National Park in Wyoming has may geysers.

12. Earth’s Temperature • Temperature increases 2 – 3 degrees C for every 0.1km (300ft) below the surface. • The deepest holes ever drilled are less than 15km (9mi). • Geysers, Volcanoes, seismic waves help scientist learn about earth’s interior.

13. MOVING PLATES - 1915 • Alfred Wegener, German meteorologist & geologist • Felt continents were moving slowly across Earth’s surface • Wegener’s theory is known as The Theory of Continental Drift • His theory was rejected

14. MOVING PLATES - 1950 • Scientist believed the lithosphere was broken up into giant slabs of rock called plates. • This idea is called Plate Tectonics. • They move an average speed of 4 inches per year • Two kinds of plates: Oceanic plates & Continental plates

15. Oceanic Plates Consist of dense ocean-floor material Continental plates Made up of lighter continental rock “riding” on top of denser rock PLATES

16. Types of Plate Boundaries

17. Converging Boundaries • Two plates move toward each other. • One plate may move under the other in a process called subduction. • Oceanic & Continental plates converge. • Denser rock of oceanic plate slides under the lighter continental plate

18. Diverging Boundaries • Two plates move away from each other. • Molten rock rises to fill the gap, creating new crust. • Usually happens in the middle of the ocean floor • Referred to as sea-floor spreading

19. Sliding Boundaries • Two plates slide past each other, moving in opposite directions. • This happens along what is known as a fault line.

20. Evidence for Moving Plates • Rocks • Studying the layers of rocks shows how they were deposited • Fossils – the physical remains or traces of plant or animal that lived long ago • Fossils found in sedimentary rock

21. Fossils • Fossils of similar species have been discovered on opposite sides of an ocean. • This helps scientist understand how plates move. • Fossils of tropical plants and animals have been found in polar regions. PHOTO - CAMBRIAN TRILOBITE

22. REVIEW

23. Earth’s _____, consists of metals. • Inner core

24. Where the upper mantle and crust meet. • Lithosphere

25. ______ is a theory that describes how large slabs of the lithosphere move.. • Plate Tectonics

26. Which is the thickest of Earth’s layers? • Mantle

27. How can fossils provide evidence to support the theory of plate tectonics? • Fossils of tropical plants and animals may be found in polar regions.

28. List three ways scientist can learn more about what goes on beneath Earth’s surface. • Study rocks drilled from the crust • Volcanoes • Geysers

29. Measurements indicate that the distance between Africa and South America is increasing. What do these measurements indicate about the portion of Earth’s crust between Africa & South America? • Africa & South America are located on different plates. There is a diverging boundary between the two plates.

30. Explain what happens to rock along converging boundaries. • Plates collide and rocks compress and break. One plate may move below the other plate.

31. Besides plate movement, describe one process that can alter the structure of Earth’s mantle. • Weathering, erosion, or depostion can create plateaus, mesas, caves, sand dunes, alluvial fans, barrier islands

32. Describe evidence of high temperatures below Earth’s surface. • Scientists encounter higher temperatures when they drill. • Rocks melt below the Earth’s surface. • Geysers spew hot water from beneath the surface.

33. Describe one way mountains may have formed. • Magma rose near the surface but did not break through. • Faulting caused one plate to rise above another plate. • Erosion by wind and rain rounded the surface over time.

34. The End