GEOL 106 Lecture Notes - Inner Core, Continental Crust, Water Cycle
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23 Nov 2011
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What causes the stress in the earth?
• That’s what we need to answer now. So lets look at the
dynamic earth system more closely
Structure of the earth
• Seismic waves have been critical in giving us a “picture”of the
inside of the earth ( an “xray” of the Earth ). The waves are
reflected and refracted at boundaries between different
materials.
• Waves reveal a layered earth
• P and S wave .. P waves can go through liquid .. s waves
cant.. determines 3 layers. Mantle, Outer core and Inner core.
We live on crust. 2900 km from crust to get to outer core (
depth of mantle) .. 5100 km from crust to get to core… 6371
km to get to centre of earth. Mantle (solid) outer core (liquid)
inner (solid) .
• Continental crust in about 30 km thick and oceanic crust in 5
km thick.
• Moho is the boundary between the crust and mantle.
• Moho stands for Mohorivicic Discontinuity ..
What about the composition of the layers.
• The core of the earth . outer/inner is mostly out of iron (Fe).
And the mantle is made out of minerals called silicates (O, Si,
Mg, Fe,Al,etc ) .. Iron, oxygen, silicon , aluminum ,
magnesium (Silicates :minerals that have O and Si as their
basic building blocks)
• Chemical Composition of Mantle .. order of decreasing
abundance (by weight) … O. Si. Fe. Mg. etc
• Chemical composition of average crust. (ie. Continental and
oceanic crust combind.) order of decreasing abundance (by
weight). O. Si. Al. Fe. Ca. etc
• Difference between continental crust and oceanic crust.
o Continental :
More Si+O . Less Fe+Mg
Pink/white rocks called -> Felsic
o Oceanic :
More Fe+Mg . Less Si+O
Black rocks called - Mafic .. rich in mafic
minerals M for Mg and F for Fe.
Minerals with Fe in them are generally black
Increase in Fe content and Density
• Cont crust ------ Felsic