Internal structure of the earth: earth is layered and dynamic, the internal structure of earth can be considered in two fundamental ways: Juan de fuca plate matters in canada: everything we talk about is the crust; earthquakes etc. Inner core: 1300km in thickness, high temperature, composed or iron (90%) and other elements (sulphur, oxygen and nickel) Outer core: 2000km in thickness, composition similar to the inner core. Mantle: 3000km in thickness, composed of iron rich and magnesium-rich silicate rocks. Crust: outer rock layer of earth, mohorovicic discontinuity (between crust and mantle, separate lighter crustal rocks from more the dense mantle. Lithosphere: cool, strong outermost layer of earth. Asthenosphere: constitutes all but the uppermost part of the mantle, hot, slowly flowing layer of relatively weak rock. Convection: earth"s i(cid:374)ter(cid:374)al heat (cid:272)auses (cid:373)ag(cid:373)a to heat up a(cid:374)d (cid:271)e(cid:272)o(cid:373)e less de(cid:374)se, the less dense magma rises -cooler magma falls back downward.