Agroup of scientists studied seismic waves and observed that the speed of seismic waves changes as they travel deeper into the earth. based on the scientists' observations, it can be concluded that earth may have layers made of the same materials empty caverns deep under earth's crust the same density throughout layers of different densities

Based on the scientists' observations, it can be concluded that there may be empty caverns deep inside the Earth's crust and also layers of different densities.

Explanation:

The layers beneath the Earth's surface are distinctly dense. Some layers possess very high density, while some are comparatively less dense. The seismic waves travel at different speeds through layers of different densities. These waves even disappear while penetrating through some layers. This allows scientists to draw solid and reliable conclusions about the formation of the Earth's interior.

Ithink it is space that makes up 70 percent