Earth's Internal Structure → Layers

coremantlecrust

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.