Earth's
interior is subdivided in two different classifications (Fig. 5,
right, click to zoom in):
Based on differences in
composition:
Core: mostly iron
Mantle: mostly olivine
Crust: mostly silicate; solid, separated from mantle by Moho
oceanic crust:
5-6 km thick, basaltic, relatively dense continental: 20-70 km thick,
granitic; lighter than basalt
Based on differences in
rock behavior:
Inner core: solid
Outer core:
molten (source of Earth's magnetic field) Inner mantle: mostly
solid, but flows over millions of years
Asthenosphere: behaves like soft butter; part of mantle;
present to about 350 km depth
Lithosphere: solid, cold; includes crust and outermost mantle;
about 100 km thick;
Plates -- part of the lithosphere
-- probably are carried along on top of the asthenosphere as the latter
flows due to convection in the mantle. Convection, in turn, is driven
by Earth's loss of heat. Thus: