core
core Central area of the Earth from a depth of 2885km (1790mi). It accounts for 16% of the Earth's volume and 31% of its mass. Information about the core is obtained from the measurement of seismic waves. These indicate that the outer part of the core is liquid, because shear (S) waves will not travel through it, whereas the inner core from 5150km (3200mi) to the centre of the Earth is interpreted as solid because seismic velocities are lower. It is believed that the change from liquid to solid core occurs because of immense pressure conditions. The core is thought to be composed of iron-nickel alloy (90% iron, 10% nickel). Temperature estimates for the core vary from 4000 to 7000°C (7200–12,600°F). Convection in the iron liquid outer core is thought to be responsible for producing the Earth's magnetic field.
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core