An Etymological Dictionary of Astronomy and Astrophysics
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The upper zone of the → Earth's core, just below the → mantle, extending from a depth of about 2900 km to 5100 km. It is presumed to be → liquid because it sharply reduces → compressional wave velocities and does not transmit → shear waves. Its density is from 9 to 11 g/cm³. The → temperature ranges from 4400 °C in the outer areas to 6100 °C near the → inner core. Since shear waves do not propagate through a fluid, the Earth's outer core is considered to be liquid because the shear wave velocity is zero. Convection motion within the outer core, along with the rotation of the Earth creates an effect that maintains the Earth's → magnetic field.

→ outer; → core.