One could think that Earth is a just a solid structure but, in reality, Earth’s crust is basically floating on magma—molten rock which is semi-liquid below the crust. Earth scientists have come to belief that Earth’s core is composed of nickel and iron. check her latest blog posted at http://www.polarisnet.ca/geology-education/
Scientists are able to determine this since Earth’s interior experience high temperatures and pressure making traveling there impossible and, in fact, even the deepest oil wells go down only a few kilometers. It is through the measurement of seismic waves that scientists are able to measure Earth’s internal structure. Earthquakes are common today, from the devastations of Haiti to constant threats in Island nations like Japan, earthquakes are common hazards.
Earthquakes produce seismic waves from their vibrations; these waves travel to Earth’s interior and are measured using seismographs. To understand earthquakes and seismic movement around the world, it is essential first to study the different types of seismic waves.
Generally, there are two main types of seismic waves: Surface and body waves but its only body waves that are used in determining the Earth’s internal structure. Body waves are divided into P waves and S waves. These two waves are the ones used in determining Earth’s internal structure.
• P Waves – They are knows as primary or pressure waves. They travel in a legion of compression and are the fastest seismic waves. Essentially, longitudinal P waves are able to move even through a solid and fluid rock just like water. It then pulls and pushes through the rock the same way air is pulled and pushed by sound. A perfect example is when a big clap is able to rattle the windows, thus the window are able to rattle just because of the pushing and pulling of the sound waves just like how the rock is pulled and pushed by the P waves going through it
• S Waves – Also known as shear waves, they travel like vibrations and the second you would feel during an earthquake. The wave is slower than its counterpart the P waves and cannot get through a liquid. This is due to the fact that liquids are not rigid in order to transmit S waves. visit this link for additional tips.
Scientists are able seize the information about the movement of seismic waves in the Earth to determine the earth’s internal structure. P and S waves are not only generated by earthquakes but they can also be generated by meteors when they hit Earth, volcanoes and even large machinery or huge explosions can create them. Basically, the P and S waves from earthquakes do not have a constant speed or travel straight.
Using the seismic waves, scientists have managed to determine the Earth’s internal structure. Since both waves travel at their own speeds and through different materials, the waves help locate the epicenter of an earthquake. Evidently, scientists say that the internal structure of Earth has changed dramatically over time through a process of differentiation. It is critical therefore, to lighten human activity and work towards limiting these waves as they would be the cause of Earth’s undoing.