Earth’s Interior & Convection Currents and the Mantle

1. Earth’s Interior&Convection Currents and the Mantle Ms. Luginbuhl

2. The Science of Geology • Geologists are scientists who study the forces that make and shape the Earth. • Study rocks, the material that forms Earth’s hard surface • Geologists study the processes that create Earth’s features and search for clues about Earth’s history. • Water, wind and waves

3. Studying Surface • Constructive forces shape the surface by building up mountains and landmasses. • Destructive forces are those that slowly wear away mountains, and, eventually, every other feature on the surface. • Example: ocean waves

4. Finding Evidence • What’s inside Earth? • It is 6,000 kilometers to Earth’s center! • Seismic waves are produced by earthquakes. • Scientists study how waves travel through Earth to learn about what is in the interior that we cannot reach. This is how we know there are several layers below Earth’s crust. • This is an example of indirect evidence!

5. Finding Evidence • Scientists can also study rocks from different depths. • Drilling • Blasted from inside Earth to the surface • This is an example of direct evidence!

6. The Center of the Earth • 3 main layers make up Earth’s interior • Crust • Mantle • Core

7. The Crust • Outer layer • Land surface (dry) and ocean floor (wet) • On average, 32 km thick • Solid and rocky • Basalt is dark rock with fine texture. It is typically found in the oceanic crust. • Granite is light in color and has a course texture. It is typically found in the continental crust. • Oxygen, silicon, aluminum, calcium, iron, sodium, potassium and magnesium

8. The Mantle • Goes almost halfway to the center of Earth • About 3,000 kilometers thick • Very hot, solid rock • Upper Mantle: • Lithosphere - rigid • Asthenosphere – softer, still solid, but capable of flow • Lower Mantle: Solid to Earth’s core. • Pressure and temperature increase as you go deeper in the mantle • Silicon, oxygen, iron, magnesium

9. The Core • 2,000 degrees Celsius to 5,000 degrees Celsius • May be as hot as the sun’s surface! • Outer core: liquid, molten, metal • Inner core: solid metal (because the pressure is so high the metal cannot spread out to be liquid!) • Iron and nickel

10. Earth’s Magnetic Field • The liquid outer core causes the solid inner core to spin, resulting in Earth’s magnetic field. • Think giant bar magnet!

11. Heat Transfer Between the Layers • Recall that heat transfer is the movement of energy from a warmer object to a cooler object. • Radiation • No direct contact (think sun rays) • Conduction • Direct touching (think the person that sat in your seat before you warmed it up) • Convection • Movement of a heat through a fluid

12. Convection Currents • The heating and cooling of a fluid, changes in the fluid’s density, and the force of gravity combine to set convection currents in motion. • Without heat (source), the convection current will eventually stop because the material will have become all the same temperature.

13. Earth’s Interior Review Questions • What are two things that geologists study about Earth? • What are the layers that make up Earth? Write a sentence about each one. • What happens in Earth’s interior to produce Earth’s magnetic field? Describe the layers of the interior where the magnetic field is produced. • What are some of the differences and similarities between the mantle and the core? Explain.

14. What are two things that geologists study about Earth? • Geologists study… • Forces/processes that make and shape Earth • Chemical and physical characterizes of rock • Earth’s history

15. What are the layers that make up Earth? Write a sentence about each one. • The crust is the outer layer of rock. • The mantle is the middle layer of very hot rock. • The core is liquid and then solid and the innermost part of Earth.

16. What happens in Earth’s interior to produce Earth’s magnetic field? Describe the layers of the interior where the magnetic field is produced. • The liquid outer, molten metal core has currents which cause the solid inner, solid metal core to spin.

17. What are some of the differences and similarities between the mantle and the core? Explain. • Answers will vary.

18. Convection Currents and the Mantle Review Questions • What are the three types of heat transfer? • Describe how convection currents form. • In general, what happens to the density of fluid when is becomes hotter? • What happens to convection currents when a fluid reaches a constant temperature? • What will happen to the flow of hot rock in Earth’s mantle if the planet’s core eventually cools down? Explain your answer.

19. What are the three types of heat transfer? • Radiation • Conduction • Convection

20. Describe how convection currents form. • A convection current forms when there is heating or cooling of a fluid. The fluids density changes and because of this, gravity acts on the fluid, causing the less dense part of the fluid to move towards the top and the more dense fluid to settle below it.

21. In general, what happens to the density of fluid when is becomes hotter? • Hotter – less dense • Colder – more dense

22. What happens to convection currents when a fluid reaches a constant temperature? • When a fluid reaches a constant temperature the convection current stop because there is no longer a difference in density throughout he fluid and for this reason no longer motion.

23. What will happen to the flow of hot rock in Earth’s mantle if the planet’s core eventually cools down? Explain your answer. • If the core cools down, there will be less flow of hot rock because there will not be as much of a temperature difference between the layers resulting in not as big of a difference in density so not as much movement of fluid.