How do geologists use seismic waves to learn about the earth's interior?

Seismic and the Earth. they came. Geologists use these records to establish the structure of Earth's interior. The two principal types of seismic waves are P-waves (pressure; goes through liquid and solid) and S-waves (shear or secondary; goes only through solid - not through liquid).

Because geologist cannot directly study the interior of Earth, they often use information from seismic waves to infer information. The speed of the waves and the paths that they take through the Earth can tell geologists a lot about the materials though which they travel.

brave new world, aldous huxley (1932)

i'm sure the answer you are looking for would be

a. an ice age

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