Differentiation and the internal structure of the earth

 

REVIEW

Accumulation and the Nebular Hypothesis

The 4 states of matter

The standard disclaimer...

"As usual, what you are about to hear is only our best guess."

The earth is not the same from the surface to the center

Appears to be layered by density

The earth is a lot like an egg (demo?)

Describe how egg is similar to earth's internal structure (Transparency #26)

Core: iron and nickel

Mantle: silicates (probably ultramafic in composition)

Crust: silicates (primarily basalt and granite)

This layering is the result of differentiation

Very important so pay attention!

Density differences - the driving force

Examples:

Oil and water

Water and mercury

Pepsi cans

Candle in the wind

ORBITZ soft drink

Anyway, density differences have resulted in the current layering of the earth

Heaviest stuff in the center, lighter as we move to the surface

 

How all this affects the formation of the crust

The crust is the important part - it's where we live!

The lightest "scum" is accumulating at the surface

Cools where exposed to space

Results in igneous rocks

Form the vast majority of the crust

Primarily composed of one of two fundamentally different rock types (mafic vs. felsic)

Basalt - dark and heavy (specific gravity 3.2)

Forms the relatively low-elevation crust beneath the ocean basins

Refer to Physiographic map

Granite - much lighter rock (s.g. 2.7)

Because granite is less dense, it tends to ride higher in the crust

Forms the major continental land masses.

Essentially floating in a 'sea of basalt'

Both basalt and granite are 'igneous' rocks

Crystallized from magma: the molten (liquid) phase of solid rock

We will discuss how these crustal materials are evolving for the next couple weeks

Definitely an on-going process