Earth's Internal Structure → Layers core mantle crust These are identified using seismic waves p-waves & s-waves

Earth's Internal Structure - significance to oceanography - explains ocean floor characteristics - determines distribution of oceanic and terrestrial components of crust - most crustal activity associated with plate tectonics occurs in oceans, not on land

Earth's Internal Structure - characterized by gradients Remember this about Earth: going deeper means significant increases in - temperature - pressure - density These gradients explain much about Earth, including many ocean characteristics

Inner and Outer Core Inner core - solid metal, mostly Fe some Ni, many other heavy metals Outer core - liquid metal containing some crystallized solids - flows in response to rotation of Earth (km/yr) - circulation of liquid metal causes Earth's magnetic fields The core's heat is generated by the many radioactive elements it contains.

The Mantle 70% of Earth's volume Mg-Fe-Si compounds, rocky, not metallic Heated from below by the core → convection motion Considered mostly solid, but able to flow very slowly (cm/yr) The circulating convection currents in the mantle are the cause of plate movement on the surface.

The Crust Two types of crust : Oceanic and Continental Continental crust - lighter silicates Na, K, Al - less dense, much thicker Oceanic crust - heavier silicates Ca, Mg, Fe - higher density, thinner The relative densities of crust silicates determine their actions during plate movements.

These layers are compositional But there are two ways to view Earth's layering: - by considering the layers' compositions - by considering their functions (mechanical)

Mechanical Layers Layers are defined by changes in the mechanical properties of rock - from rigid to ductile behavior. Rigid rocks do not deform or flow under force Ductile rocks deform or flow under force The rock layers that are defined by these criteria are the lithosphere, asthenosphere and mesosphere.

Earth's “other” layers - Lithosphere - Crust and upper Mantle - Asthenosphere - mid portion of the Mantle - Mesosphere - lower Mantle These layers are defined by their mechanical properties and the way they function with plate tectonics

Mechanical Layers Lithosphere - the strong, rigid surface shell that moves as a single plate - consists of crust & upper mantle fused together - base occurs ~650C → Mantle rock looses strength Asthenosphere - molten portion of Mantle - partial rock melting as temp increases with depth Mesosphere - increased pressure causes rock to re-solidify

Earth's Layers It is important to understand all the relationships between the mechanical and compositional layers.