How are earthquake waves used to provide information about earths 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).

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

a. an ice age

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