Theory question 203
Structure of the Earth(a) Draw a well-labelled diagram to show the internal structure of the earth. (b) Describe the main features of any two of the parts shown in 3(a) above.
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(a) Concentric diagram labelled: crust (sial over sima), Mohorovicic discontinuity, mantle, Gutenberg discontinuity, outer core (liquid), inner core (solid).
(b) Crust: outermost thin layer, 5-10 km under oceans and up to 60-70 km under continents; sial (silica and aluminium, granitic, density about 2.7) forms continents; sima (silica and magnesium, basaltic, about 3.0) forms the ocean floor; supports life and soils.
Mantle: about 2,900 km thick; dense ultrabasic rocks rich in iron and magnesium (olivine); very hot; upper part partly molten (asthenosphere) where convection currents move plates.
Core: radius about 3,400-3,500 km; made of nickel and iron (nife); very dense and hottest; outer core liquid, inner core solid; gives the earth its magnetism.
Label the layers in order from outside in and give thickness and composition for each one you describe.