1. Formation and Layers of Earth

2. A little about Earth’s background… Approximately 4.6 billion years ago, scientists believe that the Earth and other planets in the solar system formed. ◦ The formation of the planet generated heat from gravitational energy and the decay of radioactive elements, which are still present on Earth today!

3. Let’s go to China!! If you wanted to dig a hole to China, do you think you would be able to? Why or why not? Compare this apple slice to the interior of the Earth. How does each layer of the apple correspond to each layer of the Earth? Revised from: http://www.slideshare.net/melissameasley/earth-layers-density

4. Why haven’t we explored inside of the Earth? We have explored outer space much more extensively than we have explored the inside of our own planet. Why haven’t we explored the inside of our planet more completely?

5. Reason 1- HEAT  Heat  The Earth gets hotter as it gets deeper.  The Earth gets up to 9000 degrees F in the inner core. ▪ Crust = 0 -1598 F ▪ Mantle = 1598 F – 3992 F ▪ Outer Core = 3992 – 9032 F ▪ Inner Core = 9032 F+  The Kola peninsula drilling project well (in Russia) reached temperatures of 180 degrees C (356 degrees F), and they weren’t even halfway through the crust!Kola peninsula drilling project well ▪ Food cooks well at 350 degrees F.

6. Reason 2- PRESSURE ◦ The pressure increases as depth increases in the Earth from all the layer and matter on top of it squishing it down. ◦ Just 30 miles down into the Earth the pressure reaches pressures of around 200,000 psi.  Your bike tire only hold around 32 psi. (psi = pounds per square inch). ◦ The pressure at the center of the earth is estimated at around 5 million times atmospheric pressure (the 15 pounds/square inch that we breathe and live in).

7. Reason 3- Earth isn’t Accessible  Getting into the earth is very difficult because of tremendous heat and pressure.  The Kola peninsula drilling project well (in Russia) was the deepest well ever drilled into the Earth. It took 24 years, and it is less than 13 kilometers (about 7.6 miles) deep.Kola peninsula drilling project well  This is less than halfway through Earth’s crust.  The furthest humans have traveled is 3.5 km (about 2.2 miles) in mines in South Africa to extract gold.

8. Reason 4- DENSITY  Three centuries ago, the English scientist Isaac Newton calculated the density of the inside layers of the Earth as twice that of surface rocks.  Our knowledge of what's inside the Earth has improved immensely since Newton's time, but his estimate of the density remains essentially unchanged.  Look at the chart at right. You can see that the density of Earth materials increase as depth increases.  The matter in the Earth is simply too compact to be able to work through. Layerand Overall Thickness Layer is Made of? Density of the Layer Inner Core5150-6500 km Solid Iron and Nickel 13.0g/cm3 Outer Core 2900-5150 km Liquid Iron and Nickel 11.5g/cm3 Mantle32-2900 km Si, O2,Fe,Mg Upper layer is mostly rocks Lower Layer is more iron and nickel 4.5g/cm3 Crust0-32 kmSi, O2, Al, Ca, Fe, Na, K, Mg Mostly rocks 2.7- 3.0g/cm3

9. Why is the inside of the Earth divided into layers? By the end of the day today, you should be able to… 1. Define density. 2. Explain the difference between objects that are more dense and objects that are the least dense. 3. Identify objects that are more dense and less dense in comparison to each other 4. Relate these concepts to Earth’s layers.

10. What do we call this?

11. The Earth has 4 separate layers… How do we know this, anyway? Brief explanation of seismic waves: http://www.youtube.com/watch?v=yOGoKCK17a4 (1:40)http://www.youtube.com/watch?v=yOGoKCK17a4 (We will discuss seismic waves in much more depth later! For now, just know that these waves have “shown” us that there are different layers, even when we cannot physically see them!)

12. First, some density background information (this should be review): Density = mass/volume Density is the science-y word for “heavy” More dense materials sink Less dense materials float Gravity pulls ___________________.

13. Question to ponder… Why does Earth’s interior separate into layers instead of mixing together? ◦ Answer this at the top of your density column page! We will do a lab today to show you why!

14. Density Column Lab!

15. What does the density column lab tell you about Earth’s layers? As the planet was formed, the heavier elements sunk to the core of the earth, while the less dense elements stayed in the crust. Planetary differentiation – a process where more dense materials sink to the center, while less dense materials stay on the surface.

16. Layers of the Earth Rap video: http://www.youtube.com/watch?v=Q9j1xGaxYzY

17. The Layers of the Earth © Copyright 2006. M. J. Krech. All rights reserved.

18. The Four Layers The Earth is composed of four different layers. 1. The crust is the layer that you live on, and it is the most widely studied and understood. 2. The mantle is much hotter and has the ability to flow.

19. The Four Layers (continued) The outer core and inner core are even hotter with pressures so great you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!

20. The Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The thickness of the crust varies. Crust beneath the ocean, called oceanic crust is less than 10 km thick Crust beneath the continents, called the continental crust, is about 32 km thick.

21. The Lithospheric Plates The crust and the stiff upper part of the mantle together make up the rocky lithosphere.

22. The Lithospheric Plates The crust and the whole lithosphere are broken into many parts called p lates.

23. The Asthenosphere The plates "float" on the softer part of the upper mantle, called the asthenosphere. This allows the plates to move. Occasionally they will stop moving but when they stick in one place they build pressure until then snap.

24. The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.

25. The Crust The crust is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this the less dense continents ride on the denser oceanic plates.

26. The Mantle The Mantle is the largest layer of the Earth. The mantle is made up of extremely hot rock composed of the elements silicon, iron, oxygen, magnesium and sulphur.

27. The Mantle The boundary between the crust and the mantle is called the Moho. Here the temperature of the Earth is about 870  C. As you get deeper into the mantle the temperature rises until it reaches a top heat of around 3700  C.

28. Convection Currents The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again -- repeating this cycle over and over.

29. Convection Currents http://www.absorblearning.com/media/attachment.a ction?quick=12p&att=2775 The next time you heat anything like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration

30. The Outer Core The outer core starts at 2,900 km (1,800 miles) beneath the surface of the Earth and it is about 2,350 km thick. At its hottest point the outer core will reach a temperature of 6,100  C. This is so hot that the entire layer is liquid.

31. The Outer Core This area of the Earth is made up of molten nickel and iron. This moving mass of molten metal together with the inner core creates Earth's magnetic field.

32. The Inner Core The inner core begins at 5,150 km (4000 miles) below the Earth’s surface. The inner core is about 1,300 km (800 miles) thick. The highest temperature is 7,000  C.

33. The Inner Core At this temperature the iron and nickel that make up the inner core would be liquid were it not for the intense pressure in this layer. Because of the pressure the inner core is solid.

34. The End BONUS: Find a pair or trio and answer this question: Have we ever seen part of the Mantle? Explain. © Copyright 2006. M. J. Krech. All rights reserved.