1. How Are Things Sorted Again?!
*Earth materials are sorted based on 1) DENSITY, and 2)PARTICLE SIZE.
The density formula: DENSITY = MASS ÷ VOLUME
Denser substances will sink below less dense substances.
Larger particles will be deposited beneath smaller particles.
Before settling:
After settling:

2. *Layers- They’re Everywhere!!
Examples of sorting & layering in nature:
A road cut or canyon wall
A riverbed
A beach
Our atmosphere
Can you think of any others???

3. *What does the Earth look like on the INSIDE?!
See Scrat video clip:

4. The Structure of the Earth:
The Earth is made up of several distinct layers, each with its own unique properties and composition.
Atmosphere
Crust
Mantle
Outer core
Inner core

5. Some OUTSIDE Layers: Other Outside Layers:
- ATMOSPHERE = the layer of air that surrounds and envelopes our planet.
*Average density of air = g/mL
- HYDROSPHERE = all the water that covers the Earth’s surface (oceans, lakes, rivers, ice, etc.).
*Average density of water = 1 g/mL
*Even these 2 layers have layers!!

6. The CRUST (ROCK solid):
CRUST = the outermost layer of the Earth
Thinnest of the 3 inner layers.
Two types: oceanic crust (thin; like basalt) and continental crust (thicker; like granite)
We know more about this layer than the other two internal layers.
*Broken into pieces
(“tectonic plates”):

7. The MANTLE (hot, thick, and gooey):
MANTLE = the layer between the crust and the core;
Made up of magma (molten rock)
Is very thick and contains most of the Earth’s mass.
Volcanoes~ ”windows” in the crust that allow us to study the mantle.

8. The CORE (made of metals):
CORE: the layer that extends from the bottom of the mantle to the center of the Earth
- Mostly made of iron, with smaller amounts of nickel
- Under extreme heat and pressure
*Is slightly bigger than the planet Mars!
- Can be divided up into 2 smaller semi-layers: the outer core (a liquid) and the inner core (a solid).

9. More About The Core…
- Studying how seismic waves from earthquakes travel through the Earth has led to many important discoveries concerning its interior.
*P waves (Primary) are the fastest and can travel through any state of matter.
*S waves (Secondary) are slower, and can’t travel through liquids!
*This was how scientists confirmed that the outer core was a liquid!

10. Our Friend, Density! 
The Earth’s internal and external layers are all sorted by their different densities (see the chart)!!
*Atmosphere = g/mL
*Hydrosphere = 1 g/mL
*Crust = g/cm³
*Mantle = – 5.7 g/mL
*Outer Core = g/mL
*Inner Core = – 13 g/cm³ →

11. *Studying the Earth Through Core Samples!
Drilling a core sample:
Examining the sample:
Let’s make one of our own!!

12. Models
A model is used to demonstrate something that is either too big or too small to see easily

13. *What are some accurate & inaccurate features in these Earth models?

14. *Check out Antarctica- it goes on forever!!
Maps:
MAPS are reliable for navigating the road, but don’t make the best models of our planet. They are flattened, one-dimensional drawings that must stretch certain parts of the Earth out of proportion in order to fit it all on the map.
Equal-area projection maps stretch out the equator,…
While mercator projection maps stretch out the North & South Poles.
*Other inaccurate features:
Doesn’t show the Earth’s topography (ocean trenches, mountains, etc.).
Equal-area Projection:
Mercator Projection:
*Check out Antarctica- it goes on forever!!

15. *What about a globe model?

16. Globes:
GLOBES are better models than maps, but still have a few problems. For example, the topography (mountains, valleys, etc.) at the surface may not be built to scale.
*Other inaccurate features:
The Earth isn’t perfectly round, but actually bulges along the equator.
The Earth is tilted 23.5 degrees.
Doesn’t show the Earth’s interior.

17. *What’s wrong with a cross-sectional diagram?

18. Cross-sectional Diagrams:
CROSS-SECTIONAL DIAGRAMS show the interior of the Earth quite well, but the thickness of the crust and other layers is frequently drawn out of proportion.
*Other inaccurate features:
The crust is not the same thickness all around the world.
The layers don’t have definite boundaries, but rather blend together along their borders.

19. *Other Problems With Earth Models:
Maps, globes, and other models don’t move. Continents and tectonic plates in the crust are constantly moving.
The Earth’s features are constantly changing (changes in country boundaries, the creation of small islands, etc.), so models become outdated very quickly.
A new edition of the National Geographic “Atlas of the World” just came out. Since the last edition 5 years ago, there had been over 15,000 changes!!
Any others you can think of?!

20. *Is It Even Possible?!
Due to its complexity and changing features, it’s near impossible to make an accurate Earth model.
Models are still helpful and serve many useful purposes though!