1. Journey to the Center of the Earth
Topic 12
Regents Earth Science

2. Objectives Describe the Earth’s internal structure.
Explain the changes in P and S wave velocities in the Earth.
Describe the shadow zone and explain its significance.
Use the ESRT to describe various properties of the Earth’s interior such as pressure, temperature, and density.

3. The study of seismic waves allows scientists to “see” inside the earth.
Scientists have discovered that seismic waves
refract
reflect
change velocity
and become absorbed by various parts of the Earth’s interior

4. Changes in the speed of seismic waves were used to determine the location of the Earth’s different layers

5. Layers of the Earth
Crust
Mantle
Outer Core
Inner Core

6. Crust This is the layer that we live on
The thickness ranges from 8 km under the oceans to 40 km under the continents
Continental crust is thickest beneath high mountains
It is the thinnest layer of the earth

7. Comparing Oceanic and Continental Crust
Oceanic Crust
Composition is “basaltic”
Density about 3.0 g/cm3
Younger (180 my old or less)
Continental Crust
Composition is “granitic”
Density about 2.7 g/cm3
Older (4 by old)

8. Mohorovicic Discontinuity
Called Moho
Is the boundary between the crust and mantle
Was discovered in 1909 by Andrija Mohorovicic
He found that seismic waves increase in speed at an average depth of 40 km.

9. The Mantle It consists of magnesium, iron, and silicon
Is divided into 2 regions
It consists of magnesium, iron, and silicon
It is 3000 km wide
It is more rigid closer to the surface

10. The Upper Mantle Rigid Mantle Plastic Mantle Cool and brittle
The rigid mantle and crust make up the lithosphere
Divided into sections called plates
km thick
Plastic Mantle
Partially molten - the rock in this layer has the ability to flow.
Also known as the asthenosphere
Magma originates here
About 200 km thick

11. The Outer Core liquid 2100 km wide consists of nickel and iron
flow of iron creates the Earth’s magnetic field

12. How do we know the outer core is liquid?
S-waves do not pass through this zone
Shadow zone - no p-waves or s-waves received here
103° to 143° from focus

13. At the outer core Thers is a sudden decrease in p-wave velocity and
S-waves disappear

14. The Inner Core solid consists of the metals nickel and iron
temperature is 6,000° C
width = 2,100 km

15. The Earth’s Interior
ESRT page 10

16. Selected Poperrties of the Earth’s Interior
The x-axis shows the depth from bottom to top.
As depth increases, pressure increases.
1 atmosphere = 14.7 psi or “normal” air pressure at sea level
As depth increases, density increases.

17. Melting Point and Temperature
As depth increases, temperature increases.
What evidence can you see for a liquid outer core?