1. Chapter 4 - Plate Tectonics
Inside the Earth
Restless Continents
The Theory of Plate Tectonics
Deforming the Earth’s Crust

2. Inside the Earth

3. Earth’s Layers
Inner Core
Outer Core
Mantle
Crust

4. The Earth’s Crust Outermost layer of the Earth 5 – 100km thick
Less than 1% of the mass of the Earth, yet humans have not ever drilled all the way through it.
Two types:
Continental Crust
Oceanic Crust

5. Mantle Continental Crust - Thicker and less dense
Oceanic Crust - Thinner and more dense

6. The Earth’s Mantle Between the crust and the core 2900 km thick
67% of the Earth’s mass
Three parts
Lithosphere (half in the crust)
Asthenosphere
Mesosphere

7. Layers of the Mantle

8. Layers of the Mantle
-- Lithosphere is the rigid layer of the Earth that includes the crust and the upper part of the mantle.

9. Layers of the Mantle
-- Asthenosphere is the soft plastic-like layer of the mantle on which the pieces of the lithosphere float.

10. Layers of the Mantle
-- Mesosphere is the strong lower part of the mantle.

11. The Core Innermost layer of the Earth 3430 km radius
33% of Earth’s mass
Made mostly of iron
Two layers
Outer core
Inner core

12. Layers of the Core
-- Outer Core is liquid

13. Layers of the Core
-- Inner Core is solid

14. Tectonic Plates
Pieces of the lithosphere that move around on top of the asthenosphere
These plates are made up of both continental crust and oceanic crust.

15. Mapping the Earth’s Interior
Scientists have figured out what the Earth’s interior looks like by studying how earthquake (seismic) waves travel through the Earth.

16. Seismic waves travel at different speeds when they travel through materials with different densities.

17. Scientists measure how long it takes the waves to travel through the Earth to different locations, then make calculations to figure out what the inside of the Earth is composed of.

18. Seismologists can then use the
distances and travel times to calculate the density and thickness of each layer of the Earth.

21. USGS Earthquake Hazards Program: Animation of Seismic Waves: CENTRAL ALASKA

22. Seismograph
Scientists us a device called a seismograph to measure arrival time and magnitude of seismic waves around the Earth.

23. Seismograph