1. Figure 1.CO2

2. The Earth’s Structure
series of layers or spheres which differ in density, chemistry (or composition) and physical properties.

3. Density is the relative heaviness of a substance
Or how heavy something is for its size
defined as the mass per unit volume
usually expressed in g/cm3
EARTH HAS DENSITY STRATIFICATION

4. Evidence of the Earth’s Interior Composition
Can only drill about 7.5 miles (earth’s radius = 4000 mi)
Vents, volcanoes, variation in pull of gravity, etc.
study of the shocks from distant earthquakes

5. Seismic Waves reveal that Earth’s Interior Is Layered
If Earth were uniform (homogeneous) throughout
Seismic Waves reveal that Earth’s Interior Is Layered
If the density, or rigidity, of Earth increased evenly with depth
Figure 3.7
Possible paths of seismic waves through Earth. (a) If Earth were uniform (homogeneous) throughout, seismic waves would radiate from the site of an earthquake in straight lines. (b) If the density, or rigidity, of Earth increased evenly with depth, seismic wave velocity would increase evenly with depth, and the waves would bend smoothly upward toward the surface. (c) If Earth were layered inside, some seismic waves would be reflected at the boundaries between layers while others were bent. Seismic evidence shows that Earth is layered.
If Earth were layered inside

6. Compositional Layers of the Earth
the Crust
thin outermost layer
the Mantle
thick middle layer
the Core
densest inner layer
composed mainly or iron (90%)

7. Figure 1.16

8. Figure 1.18

9. Continents and Ocean Basins Differ
2-3
Continents and Ocean Basins Differ
Continental crust
is mainly composed of granite, a light colored, lower density (2.7 gm/cm3) rock
thicker
Oceanic crust
is composed of basalt, a dark colored, higher density (2.9 gm/cm3) volcanic rock
thinner

10. Table 1.1

12. Figure 1.17

13. Physical Properties of the Layers
Not determined only by chemical composition
The behavior of the rock (brittle or plastic) is determined mainly by temperature and pressure

14. Effects of Pressure and Temperature on Physical State of Layers
2-1
Effects of Pressure and Temperature on Physical State of Layers
Increasing pressure raises the melting point of a material.
Increasing temperature provides additional energy causing material to melt.
Both pressure and temperature increase toward the center of the Earth, but at different rates.

15. Divisions of the Earth Based Upon Physical State
2-1
Divisions of the Earth Based Upon Physical State
the Lithosphere
cool, rigid outer layer
comprised of continental crust, oceanic crust and the uppermost cool, rigid portion of the mantle
the Asthenosphere
hot, slowly flowing layer of the upper mantle
the Mesosphere (Lower Mantle)
rigid layer, similar chemically to the asthenosphere but very different physically
the Outer core
thick liquid layer
the Inner core
solid layer (due to tremendous pressure)

16. Figure 1.16

17. What Are the Sources of Internal Heat That Keep the Asthenosphere Plastic?
Radioactive decay (atoms of elements give off heat when their nuclei break apart)
Internal heat moves to the surface by conduction – slow migration of heat through a material by collision of atoms
And by convection – movement of heat in a fluid as it expands, becomes less dense and rises.

18. Figure 3.11
Convection. (a) As a pot of water heats to boiling, the heated water rises. The water falls again as it cools near the surface. (b) A tectonic plate is the cooled surface layer of a convection current in the upper mantle. Plate movement is caused by the plate sliding off the raised ridges along a spreading center and by its cool, dense leading edge being pulled downward by gravity into the mantle.
Fig. 3-11, p. 57

19. Isostatic Adjustment