Earth’s Interior

1. Earth’s Interior

2. Finding Indirect Evidence • Geologist record the seismic waves that earthquakes make and study how they travel through Earth. • The speed of these seismic waves and the path they take reveals how the planet is put together.

3. A journey to the center of the Earth • Temperature – increases as you descend • Pressure (force pushing on a surface area)- the deeper you go the greater the pressure.

4. The Layers of the Earth • Crusts • Layer of rock that forms Earth’s outer skin • Includes both the dry land and ocean floor • Mantle • A layer of hot rock • The uppermost part of the mantle and the crust together form a rigid layer called the lithosphere • Temperature and pressure in the mantle increase with depth • Layer beneath the lithosphere that is less rigid then the rock above it is the asthenosphere. The material in this layer can flow slowly

5. The core • Metal iron and nickel make up both parts of the core • Outer core is a layer of molten metal that surrounds the inner core • Inner core is a dense ball of solid metal, where extreme pressure squeezes the atoms of iron and nickel so much that they cannot spread out and become a liquid.

7. Earth’s Magnetic Field • Currents in the liquid outer core force the solid inner core to spin at a slightly faster rate than the rest of the planet. • These currents in the outer core also create Earth’s magnetic field, which causes the planet to act like a giant bar magnet.

8. Drifting Continents

9. The Theory of Continental Drift • The Theory of Continental Drift • Alfred Wagener • All the continents were once joined together in a single landmass and have since drifted apart • Super continent was named Pangaea • Continental Drift – Pangaea broke apart and slowly moved toward their present day location

10. Evidence to support the theory • Evidence of Landforms – Mountain ranges in South Africa line up with mountain ranges in Argentina • Evidence from Fossils – fossils are any trace of an ancient organism that has been preserved in rock (Example – Glossopteris which is a fernlike plant that lived over 250 million years ago and was found in Africa, South America, Australia, India, and Antarctica • Evidence from Climate – Tropical plant fossils found in polar climate and deep scratches in rocks that where formed from glaciers in tropical areas

11. Sea-Floor Spreading • Mid-Ocean Ridge is the longest chain of mountains in the world and are located on the ocean floor. • Sonar is a device that bounces sound waves off underwater objects and then records the echoes of these sound waves. Scientists use sonar to study the ocean floor.

12. Evidence for Sea-Floor Spreading • The mid-ocean ridge forms along cracks in the oceanic crust • 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 • Sea floor spreading is the process by which new material is continually added to the ocean floor. • Several types of evidence is used to support sea-floor spreading – magnetic stripes, molten material, and drilling samples

13. Subduction at Deep-Ocean Trenches • Deep ocean trenches are where the ocean floor plunges into deep underwater canyons. They are formed where the oceanic crust bends toward the mantle. • Subduction – process by which the ocean floor sinks beneath a deep ocean trench and back into the mantle • At deep ocean trenches, subduction allows part of the ocean floor to sink back into the mantle, over tens of millions of years.

15. The Theory of Plate Tectonics

16. The Theory of Plate Motion • The lithosphere is broken into separate sections called plates • Wilson combined sea-floor spreading and continental drift into a single theory – The Theory of Plate Tectonics • Plate Tectonics – is the geological theory that states that pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle. • The theory of plate tectonics explains the formation, movement, and subduction of Earth’s plates

17. Plate Boundaries • Transform Boundaries – • Crust is neither created nor destroyed • Place where two plates slip past each other, moving in opposite directions

18. Divergent Boundaries • Place where two plates move apart • When develops on land, two of Earth’s plates pull apart. A deep valley called a rift valley forms along the divergent boundary

19. Convergent Boundaries • Place where two plates come together • Converging oceanic plate and oceanic plate collide one plate is subducted through a trench and volcano islands are formed • Converging oceanic plate and continental plates – when continental plates and oceanic plate collide, the oceanic plate is subducted and volcanoes on land are formed • Converging continental plates – where two continental plates collide, the crust buckles and mountain ranges form.

20. The Continents Slow Dance • The plates are moving at a very slow rate of about one to ten centimeters per year. • In areas plates are moving together and others are moving apart.