Seismic waves are energy waves able to travel through the Earth and that result from eruptions, earthquakes and other movement phenomena. The study of these waves allowed geologists who are the scientist that study the Earth to know how deep energy waves can go and how energy behaves in different levels of depth. As geologist noticed energy waves changed their speed and other features depending on the depth in Earth they were and that certain patterns repeated they could determine the Earth was composed by different levels or strata each with different features. These strata are commonly known as layers as these are levels that compose the Earth and are consistent all around it being mainly uniform; these layers include the cruts, the mantle, the outer and inner core among others. Thus, by using data from seismic waves the geologists have learned that the Earth's interior is made up of several layers. This is the correct answer as layers this the most accurate word to describe the levels or strata (plural of the word stratum) that composed Earth.
