What does the presence of earthquakes tell you about the land?
One less known of the contributions of Albert Einstein to physics is the orange model of the Earth. In this model the crust of the Earth is compared to the skin of an orange and the interior of the Earth with the pulp of the orange. Furthermore the crust of the orange is not formed by a continuous skin but by fragmented plates. The interior of the earth moves from time to time relative to its previous position and make the skin slide on its surface. Because the skin of the orange is not continuous when the interior moves, different fragments of Earth's crust slide with different speeds relative to each other. Along the lines where these fragments of skin (named plates) meet, faults are formed. This means that one plate has a different motion from the adjacent one (this relative motion can be up-down or left-right or simply one plate is pushing horizontally the other). When these relative motion happen, earthquakes occur. They happen because the sudden motion in the fault zone is transmitted through the earth different layers in the vicinity or the faults over the entire area of land. Therefore the presence of earthquakes tells us that relatively near we can find a fault in the Earth crust.