Exploring the Earth's Core
How was the Earth's core discovered? Seismic
waves from earthquakes gave the first clue.
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Seismic waves will bend and reflect at the interfaces between different materials. The two types of seismic wave behave differently, depending on the material. Compressional P waves will travel and refract through both fluid and solid materials. Shear S waves, however, cannot travel through fluids like air or water. Fluids cannot support the side-to-side particle motion that makes S waves. |
Earth's Magnetic Field
Paleomagnetic records indicate that the geomagnetic field has
existed for at least three billion yrs. Based on the size
and electrical conductivity of the Earth's core, the field
would decay away in only about 20,000 years. Also, the dipole polarity has
reversed many times in the past.
A mechanism within the Earth's
interior must continually generate the geomagnetic field.
This mechanism is a convective dynamo operating in the
Earth's fluid outer core.