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
• 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
• 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