Question

How do seismic waves help scientists understand Earth's layers? Select the two correct answers.
Responses

Scientists can observe which seismic waves change the composition of the layers they pass through.
Scientists can observe which seismic waves change the composition of the layers they pass through. - no response given

Scientists can observe how seismic waves change speeds when passing through different layers.
Scientists can observe how seismic waves change speeds when passing through different layers. - no response given

Scientists can observe which seismic waves cannot pass through certain layers.
Scientists can observe which seismic waves cannot pass through certain layers. - no response given

Scientists can generate seismic waves in order to observe their paths through Earth.
Scientists can generate seismic waves in order to observe their paths through Earth. - no response given

Scientists can observe how seismic waves multiply when passing through different layers.
Scientists can observe how seismic waves multiply when passing through different layers. - no response given

Answer 1

Correct answers:
- Scientists can observe how seismic waves change speeds when passing through different layers.
- Scientists can observe which seismic waves cannot pass through certain layers.

Brief explanation: seismic wave speeds (and refraction/reflection) change with density and material properties, revealing layer boundaries; also, S-waves do not travel through liquid (showing the outer core is liquid) while P-waves do, so which waves are blocked or transmitted gives information about composition and state.