Lecture 2 Earth structure Composition of the Earth
Hypsometry of the Earth -- histogram of elevation on Earth Stoddard and Jurdy 2012 Why does Earth have continents and ocean basins?
Earth’s outermost layer is the atmosphere and it is a gas At the surface, we have the liquid ocean The crust and mantle are SOLID Outer core is liquid Inner core is solid What is the difference between a solid, liquid, and gas?
Core made of Fe-Ni alloy (little to no oxygen) This is a photo of a pallasite meteorite and may represent what the core mantle boundary looks like. Green = olivine; gray = Fe-Ni alloy It is the core-mantle boundary of an asteroid.
Mantle made of olivine-rich rock called peridotite Mg, Si, O Green, green, olivine Peridot is when you’re on show Drops of water Sooner or later It becomes serpentine
Oceanic Crust made up of basaltic rocks Mg, Ca, Si, Al, O
Continental Crust made up of granitic rocks Al, Si, Na, K, O quartz
Al 1.41 Ca 1.54 ? 2.9 Ni 1.8 Fe 32.1 O 30.1 Si 15.1 Mg 13.9 7 elements make up 97% of the Earth!
Whole Earth Mantle Oceanic crust Continental crust wt % wt % wt % wt % wt % wt % wt % wt % ppm Si Al Mg Fe Ca K Na O Cu 15 1.4 15 32 1.7 0.01 0.2 32 ? 21 2.1 22 6 2.5 0.02 0.3 44 30 28 8 2 5 4 1.5 2.3 44 10 23 8 4.6 6 8 0.1 2 44 70 Wt % = 1 g per 100 g Ppm = 1 g per 1,000,000 g
Why is the Earth’s mantle depleted in Fe relative to whole Earth? Fe wt % Why are the Earth’s mantle and crusts higher in Si than the whole Earth? Si wt %
The Copper Crunch Prepared by the Resnick Institute
15,000 metric tons of Cu consumed globally How much continental crust do you have to process each year to get that much Copper? What you want What you have 1000 kg Cu metric ton Cu 1,000,000 kg crust 10 kg Cu 15000 metric ton Cu x x = 1.5 x 1012 kg crust Concentration of Cu in crust (10 ppm)
Why is the Earth’s mantle depleted in Fe relative to whole Earth? Most of the Fe is in the core! Fe wt % Why are the Earth’s mantle and crusts higher in Si than the whole Earth? When rocks melt, the melts are richer in silica. Melts rise Si wt %
Temperature (K) 1000 2000 3000 4000 0 Thermal boundary layer Upper mantle 410 14 Transition zone Temperature gets hot inside the Earth In some places, hot enough to melt 670 24 Pressure (Gpa) Depth (km) Liquidus Solidus Lower Mantle adiabat ULVZ? Asimow In Encylopedia of Volcanoes 138 3000