1. Section 3: Earth’s Interior
Chapter 12
Section 3: Earth’s Interior

2. Basic Layers of the Earth
Crust
Mantle
Outer Core (liquid)
Inner Core (solid)

3. Earth’s Crust
Continental Crust: rock layer under continents made of mostly granite
Oceanic Crust: rock layer under oceans made mostly of basalt
Basalt is much more dense than the granite. Less dense continents ride on the denser oceanic plates.

5. The Lithosphere
The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the lithosphere.
The crust is broken into pieces called plates. The lithosphere makes up Earth’s plates.

6. The Asthenosphere
The asthenosphere is the part of the middle mantle that flows gently like melted plastic.
Lithosphere or Earth’s plates ride on top of the asthenosphere.

7. Convection Currents
The middle mantle or asthenosphere moves Earth’s plates due to convection currents.
Convection currents are caused by the very hot material at the deepest part of the mantle rising, cooling & sinking again.

8. Outer Core Under the mantle is Earth’s outer core.
The outer core is so hot that the metals in it are all liquid. Outer core is made of the metals nickel and iron.

9. Inner Core
The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together to create a solid.

10. Earth’s Magnetic Field
Don’t forget: Earth’s magnetic field is caused by the spinning of the molten iron core!

11. Chapter 12
Section 1

12. Continental Drift
In 1915, Alfred Wegner hypothesized the continents were once part of a super-continent called Pangea. Over time, the continents drifted apart.

13. Proving Wegner Correct
Over time, there were three pieces of evidence found that supported Wegner’s idea:
Matching coastlines: South America looks like it fits with the coast of Africa
Matching fossils: The same fossils from ferns and dinosaurs are found on multiple continents.
Matching rocks and mountain ranges: When continents fit into Pangea, it shows mountains were originally one large mountain range.

14. Matching Coastlines

15. Matching Fossils

16. Matching Mountain Ranges

17. Sea Floor Spreading
Dr. Harry Hess used sonar to map the seafloor and revived Wegner’s ideas.
Discovered a mid-ocean ridge, or MOR, around the Earth.

18. MOR
Magma from the mantle is forced up due to its low density (convection currents).
This causes the ocean crust to crack (fault) and move apart. This is sea floor spreading! New oceanic crust is created.

19. Mid-Ocean Ridge Around the Globe

20. Mountains and Rift Valleys
The MOR creates a twin mountain range along the fault.
A rift valley is also produced with the mountain range.

21. Which crust is older?

22. Theory of Plate Tectonics
Plate tectonics- The theory that pieces of the Earth’s lithosphere are in constant motion, driven by convection currents in the mantle
No plate can move without affecting the other plates surrounding it; they must bump, grind, or pass each other in order to move.
Remember, the plates of the lithosphere float on top of the asthenosphere (the top layer of the mantle)

23. Divergent Plate Boundary
Divergent Boundary: the spreading apart of two plates. Examples: MOR and in East Africa.
Features: Rift Valley, mountain range for MOR, deep ocean trench, earthquakes

24. Transform Plate Boundary
Transform Boundary: two plates that move past each other horizontally
Examples: western US called the San Andreas Fault
Features: Earthquakes

25. Convergent Plate Boundaries
Convergent Boundary: two plates that collide. There are three ways these form:
Oceanic crust collides with continental crust
Oceanic crust collides with oceanic crust
Continental crust collides with continental crust
With convergent boundaries, subduction can occur. This is when the plate with more density sinks, melts from contact with magma, and can produce volcanoes.

26. Convergent: Oceanic and Continental
Two features created: volcanic arcs and a deep sea trench, earthquakes
Examples: Cascade and Andes Mountain Ranges

27. Convergent: Oceanic and Oceanic
Two features created: deep sea trench and a volcanic island arc
Examples: Japan, Alaskan Aleutian Islands, Ring of Fire

28. Convergent: Continental and Continental
Features: Mountain range and plateaus
Examples: Himalayas in Asia, Ural Mountain Range

29. Ch 12 Earth Analysis: Date____ Name________________ Hr__
Copy and answer in complete sentences
What causes Earth’s plates to move?
Define Convergent boundaries
Define Divergent boundaries
Define Transform boundaries
Define P(rimary) waves
Define S(econdary) waves