1. Layers of the Earth

2. Layers of the Earth
There are two ways that scientists label the layers of the Earth.
Composition layers
Physical/Mechanical layers

3. Composition layers

4. Density
Earth’s layers are characterized by many things, one of which is density.
Density is the relationship between mass and volume
Density = mass/volume
The deeper you move towards the center of the earth, the denser (and hotter) the layer!

5. Composition layers These are the more familiar layers. They are: Crust
Ranges from 5 to 100 km in thickness
Thinnest layer of the Earth
Least dense
Split into two types: Continental and Oceanic
Continental is thicker than oceanic
Mantle
Roughly 2900 km thick – the thickest layer!
No one has ever drilled to the mantle. It is also very hot
Has properties of a liquid and a solid (it is plastic)

6. Core
Mostly made of iron and nickel
Outer core: liquid, very dense
Inner core: solid from pressure
temperatures and pressures so great that the metals are squeezed together and are not able to move
The core’s diameter is roughly 6856 km (about the size of Mars)

7. Physical Layers

8. Physical Layers Lithosphere “rock sphere” (15-300 km)
The less familiar layers are the physical layers. They are based on how the layer looks or acts.
Lithosphere “rock sphere” ( km)
The tectonic plates
A combination of crust and the upper region of the mantle
Cold and brittle (easily broken)
Asthenosphere “weak sphere” (250 km)
Hard rock that acts like warm tar or honey (plastic)
Has properties of a liquid AND a solid
What the tectonic plates float on
HOT

9. Physical layers 2 Mesosphere “middle sphere” (2550 km)
Rest of the mantle
Much stronger and hotter than the Asthenosphere
Outer Core (2200 km)
Liquid layer
Inner Core (diameter= 2456 km)
Solid, dense core of the planet

10. Interesting fact… Did you know?...
The center of the Earth’s core is hotter than the surface of the sun. The temperature of Earth’s inner core reaches 6000 °C whereas the surface of the sun is roughly 5500 °C.
The sun’s core, however, is 15,000,000 °C

11. Side by side comparison
Crust
Mantle
Core
Lithosphere
Asthenosphere
Mesosphere
Outer Core
Inner Core

12. Review 1) What are the four layers of the Earth?
2) The Earth’s crust is very ______?
3) The mantle is the largest layer of the Earth? True or False
4) Is the Outer Core a liquid or a solid?

13. Answers! 1) Crust, Mantle, Outer Core, Inner Core 2) Thin 3) True
4) Liquid

14. Plate Tectonics

15. Theory of Continental Drift
Theory by Alfred Wegener
Continental drift is the theory that continents can drift apart from one another and have done so in the past.
Puzzling observations that could be explained by continental drift:
Puzzle-like fit of the continents
Fossils of the same plants and animals found on both sides of the Atlantic Ocean
Strange grooves cut by ancient glaciers that line up

16. Theory of Seafloor Spreading
Harry Hess was a geologist that studies the ocean floor
He discovered that the sea floor seemed to be pulling apart, and magma came up in the middle
This helps support Continental Drift!

17. Tectonic Plates
With the idea that continents can drift apart, scientists felt that some force had to be making these continents move.
The theory of plate tectonics developed as a way to explain continental drift

18. Tectonic Plates
Tectonic plates are large pieces of the lithosphere that move around on top of the asthenosphere like icebergs in the ocean.
There are 10 major plates

19. When plates collide!
Plate tectonics is the theory that the Earth’s lithosphere is divided into large tectonic plates that move around on top of the asthenosphere.
All plates share boundaries with other plates, just like states share borders.

20. Boundaries There are three main types of boundaries Online animations
Convergent
When plates push against each other
Divergent
When plates move away from each other
Transform
When plates slide against each other
Online animations