How have scientists been able to determine that Earth has a liquid metal outer core?
What will be an ideal response?
Geoscientists can use the arrival times of reflected and refracted seismic waves from distant earthquakes to construct a model of Earth's interior. Seismic waves from distant earthquakes pass through Earth, but a certain kind of wave, the S type, does not pass through the core. Because the S waves cannot move through a liquid, scientists conclude that Earth's core is partly liquid. Earth's magnetic field is further evidence of a liquid metallic core. The theory for the generation of magnetic fields, the dynamo effect, requires a moving, conducting liquid (for a planet) or gas (for a star) in the interior. If Earth's core were not partly a liquid metal, it would not be able to generate a magnetic field.
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