1. Journey to the Surface of the Earth, part 1
Or, Earth from the Inside-Out
September 13, 2018

2. The Earth’s Interior Today we will discuss these points:
How we know about the interior of the Earth…
How Earth’s interior took on the characteristics it has…
The layers of the Earth as defined by composition
Tomorrow we will discuss:
The layers of the Earth as defined by behavior…
September 13, 2018

3. The Differentiated Earth…
Earth shows differentiation
Separation into layers due (in this case) to differing densities
Just like separation shown here
September 13, 2018

4. How Do We Know About Earth’s Interior
Three ways, actually!
First, volcanic data brings some of the interior up to us.
Second, density information…
Since the overall density of the Earth is 5.5 g/cm3 and the density of the surface is 2.2 g/cm3, the interior must be denser!
Third, seismic (earthquake) waves act like an “ultrasound” and give a picture of the interior
September 13, 2018

5. How Do We Know About Earth’s Interior
September 13, 2018

6. How Did Earth Become Differentiated?
Earth became differentiated very early in its history (around 4.5 billion years ago) during the Great Bombardment
As material from space hit the young Earth, the heat from the impact melted the Earth leading to a magma ocean
September 13, 2018

7. Demo – How Earth Became Differentiated
Describe the demonstration you just saw and heard.
What position were the marbles in originally?
What brought about the change?
Where did the marbles end up? Why?
September 13, 2018

8. The Iron Catastrophe
The Iron Catastrophe is the name given to this event
Heavy elements (iron, nickel) sink to the center of the Earth
Lighter elements (silicon, oxygen) rise to the surface
September 13, 2018

9. So, What’s the Big Deal?
This early layering led to the way our planet functions today AND to the way life developed!
Stay tuned for more on this tomorrow!
September 13, 2018

10. Earth’s Layers Earth’s layers are defined two ways
Layers defined by composition are the core, mantle, and the crust (oceanic and continental)
Layers defined by “behavior” are the inner core, the outer core, lower mantle, asthenosphere, and lithosphere
September 13, 2018

11. September 13, 2018

12. Layers Due to Composition
Core
Innermost layer of the Earth
Composed of nickel and iron
Metallic, not rocky like the other layers
Very dense – more than 6x the density of the surface
Makes up one-third of Earth’s mass and is 3480 km thick (of 6400 km total)
September 13, 2018

13. Layers Due to Composition
Mantle
Middle layer of the Earth
Rocky, rather than metallic like the core
Composed of mafic minerals (silicates high in magnesium and iron (Fe)
High quantities of peridotite
Makes up 48% of the thickness and 67% of Earth’s mass
September 13, 2018

14. Layers Due to Composition
The Crust
Outermost layer of the Earth
Rocky, mostly silicates
Two types
Oceanic (most of the crust) – made of mafic rocks – mostly basalt
Continental – made of felsic rocks – mostly granite
September 13, 2018

15. Layers Due to Composition
Oceanic crust is very thin
Denser than continental rock.
Continental crust is thicker – up to 75 km thick
Question – since oceanic crust is denser, what happens when oceanic and continental crust interact?
September 13, 2018

16. September 13, 2018

17. Summarize… What does differentiation mean?
Why did Earth become differentiated?
In what two ways are Earth’s differentiated layers defined?
Identify one property each of the core, mantle, and crust.
September 13, 2018