Depth of the Earth is mysterious and far less accessible world than the space surrounding our planet. There is no device yet that could penetrate the depths of the planet. The deepest mine in the world has a depth of 4 km whilst the deepest borehole in the Kola Peninsula - 12 km. It's only 1/500 part of the radius of the Earth! However, people have learned to "drop in" to the depths of the Earth. The main method of studying them is seismic (from the Greek. "Seysmos" - an earthquake). From earthquakes or artificial explosions in the bowels of the earth spread fluctuations. The materials are different in composition and density, therefore, they propagate at different speeds. With the help of specific equipment it is possible to measure these velocities and decrypt information.
It is a common fact that the composition of our planet is divided into several shells: the core, mantle and crust.
Core is the central part of the globe. It is of very high pressure and temperature of 3000-4000 0C. The core consists of a very dense and heavy material, presumably iron. Core takes about 30% of the mass of the Earth, but only 15% of its volume. Internal hard part of the core appears to float in the outer layer of the liquid. Due to this movement the magnetic field occurs around the Earth. It protects life on Earth from harmful cosmic rays. The boundary of the mantle and the core has been determined on the basis that it does not go deeper than the transverse seismic waves. Since this phenomenon is observed only in fluids - it is assumed that at least the upper part of the core - flowable substance. At a depth of more than 5100 km. (Inner core), the substance presumably becomes hard. As for the composition and density of the core there are only theories. The basic assumption is that the core is composed of nickel-iron. The hypothesis has evolved from studying of meteorites’ iron which consists of Fe (90,85%) and Ni (8,5%).
Another layer of the Earth is Mantle (from the Greek. "Mantle" - blanket coat). It is the largest of the inner shells of the Earth. It occupies (80%) of the volume and (nearly 70%) of the weight of our planet. The substance is a solid mantle, but less denser than the core. The pressure and temperature in the mantle increases with depth. In the upper part of the mantle is the layer where the material is partially melted and plastic. It is suggested that the composition of the mantle corresponds to the composition of basalts and dunites.
Finally, the Earth's crust is the thinnest outer shell of our planet. The share of the earth's crust has less than 1% of the mass of the globe. In different places of the earth's crust numerous mines and boreholes are created. Millions of samples taken from them and from the Earth's surface, allowed to determine the composition and structure of the Earth's crust.
The Earth's crust is made up of rocks and rocks from minerals.
Overall, all three Earth’s layers are of great importance to be studied. They provide the scientists with the information that can lead to the answers that everyone is looking for: How old the Earth is and how was it created?
References
Earth's Layers. (n.d.). Earth's Layers. Retrieved August 25, 2013, from http://volcano.oregonstate.edu/vwdocs/vwlessons/lessons/Earths_layers/Earths_layers2.html
