Scientists<span> can tell by observing the seismic waves that are recorded all over the surface of the </span>earth<span> from distant earthquakes. The seismic waves are reflected (bounced off) </span>layers<span> of different density, and they are refracted (bent) when they enter </span>layers<span> of different density.</span>
The surrounding water is usually understood to be continuous, though not necessarily named as a single body of water.
Explanation:
