Earth’s Composition
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)
Layers of the Earth Boundaries that mark density changes between layers are discontinuities. Ex: Mohorovicic discontinuity separates the crust from the mantle.
Project Mohole 1958-1966 Attempt to dig to Mohorovicic Discontinuity
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.
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