Our understanding of the Earth's interior has been the focus of scientific study for several decades, recognized in the early 1900s. Over the years, scientists have debated and argued over their discoveries, observations and theories for the most correct model of the composition and internal structure of the Earth. Earthquakes play an important role in understanding the composition and materials that exist within the Earth (Merali and Skinner, 2009, p.252). Earthquakes are the main source of knowledge about the inner workings of the earth, due to the nature of the seismic waves they produce. P and S waves are reflected and refracted at different boundaries within the Earth, and this allows seismologists to make inferences about the internal and structural composition of planet Earth. (Merali and Skinner, 2009, p.252). In 1906, a scientist named Richard Dixon Oldham had suggested a theory that structured the findings of another scientist named Emil Wiechert. Oldham had identified that S waves and P waves behaved differently and could be used to explain and illustrate that previous theories were not entirely correct (Merali and Skinner, 2009, p.253). Through the analysis of the arrival times of these waves, Oldham had come to the conclusion that p-waves and s-waves react differently in terms of refraction, reflection or absorption depending on the state of the material, as shown in Figure 1. (Tarbuck, Lutgens, Tasa, 2013, p.143). Oldham had developed this theory that the Earth is not in the same state due to these seismic discontinuity effects shown in Figure 1., consisting of refraction, reflection and absorption. The changes visualized by this idea are; the speed of the waves due to a refraction that occurs...... in the middle of the paper...... the composition of the core and the mantle (Merali and Skinner, 2009, p.259), (Tarbuck, Lutgens, Tasa, 2013, p.397-406). Ultimately, the development of previous inferences and observations that have developed our current model for the composition and internal structure of the Earth are a key concept in understanding our future developments towards our planet's resources and understanding how it works at a further level Bibliography Merali Z., Skinner B., 2009, Visualizing Earth Science, 1st Ed, John Wiley and Sons, Hoboken, New Jersey. Tarbuck E., Lutgens F., Tasa D., 2014, An Introduction to Physical Geology, 5th edition , Pearson Education, Upper Saddle River, New Jersey. Elsasser W., 1950, Review of Modern Physics, The Earth's Interior and Geomagnetism, 22, 2-20. Herndon J. M, 2005, Current Science, Scientific Basis of Knowledge of Composition of the Earth, 88, 1034-1036)