How do we know about the layers of the earth?

Answer 1

Seismic waves have helped scientists learn the various densities of the Earth's many layers because the speed of primary shock waves moving through the earth generally increases with depth. This is because as density increases, seismic wave velocity increases. While P-waves travel through the Earth's crust at an average of about four miles (6.4 km) per second, they reach an average of seven miles (11.3 km) per second at the center of the Earth. When the shock waves suddenly shift in direction and speed, scientists are able to determine the depths at which Earth's various layers are located.

Answer 2

The crust obviously, is observable, and therefore can be studied extensively to determine its composition. Occasionally, material from the mantle has erupted onto the surface, giving us a glimpse of its contents. Additionally, we have been able to determine its density based on the study of seismic wave behavior. In fact, a great deal of our knowledge of the makeup of the Earth's interior is based on seismic wave behavior, on physics, on calculations of Earth's gravitational powers and gravitational fields, and on the study of rocks of extraterrestrial origin.

Answer 3

We know this mostly from the way different kinds of earthquake vibrations travel through the Earth, and where they are picked up. P waves can travel through liquids, but only solids can transmit S waves.

Answer 4

Earth scientists must use a combination of remote sensing techniques, inverse theory, theoretical models, and laboratory experiments to infer the properties of the Earth's interior