1. Earth’s Composition

2. Formation of Layers of Earth
OBSERVATIONS:
The Earth is not uniform!
The layers generally become denser with depth.
THEORY:
Scientists think that Earth was once molten and denser materials settled towards the core and low-density materials floated to the surface. (all due to gravity)

4. Layers of the Earth
Boundaries that mark density changes between layers are discontinuities.
Ex: Mohorovicic discontinuity separates the crust from the mantle.

5. Project Mohole
Attempt to dig to Mohorovicic Discontinuity

6. How do we know information about Earth’s interior?
Scientists have studied seismic waves.
P-waves (primary) are longitudinal and can travel through solids and liquids. They travel through liquids more slowly.
S-waves (secondary) are transverse and cannot travel through liquids.

8. Elements Found in each Layer of Earth
Core: Fe, Ni
Mantle: O (44%), Mg (22%), Si (21%), Fe (6%)
Crust: O (46%), Si (28%), Al (8%), Fe (5%)
DENSITY TREND EXISTS FOR THE ELEMENTS