Question

scientists observe that s-waves from an earthquake completely disappear when they reach a certain depth within earth. based on this seismic wave data, what can scientists conclude about earths structure at this depth?
the rock density becomes less dense
pressure causes all waves to slow down equally
the temperature increases significantly
a liquid layer exists that s-waves cannot penetrate

Explanation:

S - waves (shear waves) cannot travel through liquid. When S - waves disappear at a certain depth, it indicates the presence of a liquid layer there. The first option is incorrect as S - wave disappearance is not related to density decreasing. The second option is wrong because not all waves slow down equally (P - waves can travel through liquid), and the third option about temperature increase is not directly related to S - wave disappearance.

Answer:

D. A liquid layer exists that S - waves cannot penetrate