Geology And Geophysics

Study of the Layers of the Earth



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The earth has an equatorial diameter that is approximately 7,900 miles long. It is the largest of the of the four known terrestrial planets, i.e. planets that are composed of rock material and the only planet which can support life. The other terrestrial planets are Mercury, Venus and Mars. While human beings have traversed the earth for several thousand of years, little is known of its composition. It wasn’t until the mid 19th century that some headway was made through scientific advances that enabled a better understanding of the earth’s structure.

So what are the earth’s layers? In a nutshell, it is comprised of the crust, mantle and core. The crust is the outermost layer and is relatively thin compared to other structural layers of the earth. The crust is composed of igneous, metamorphic and sedimentary rock material. The crust can be further broken down into continental and oceanic crust. The oceanic crust also known as the oceanic plate is 3-5 miles thick while the continental crust known as continental plate is thicker at 25 miles. The crust is comprised of tectonic plates that float on mantle. While the temperatures on the outermost layer of the crust is at bearable, in the interior it may reach 1600 degrees Fahrenheit. According geological history, the earth was one large landmass called the Pangea and due to the plate tectonic movement lasting over a period of millions of years we ended up with the present day continental layout. If you were to observe the continents carefully you can be forgiven if you thought they were pieces in a jig-saw puzzle.

The next layer is the mantle which lies beneath the Moho discontinuity so named after a Croatian Geologist Dr. Andrija Mohorovicic. Dr. Mohorovicic conducted geological research focusing on the structure of the earth. Through the seismic readings he was able to determine there was a transition boundary between the upper layer of the earth and the mantle. He observed the waves transmitted from his seismograph into the earth’s interior, traveled in a different manner traveling upon reaching a specific depth. From this he was able to infer there were two distinct geological entities.

The mantle being the largest constituent matter is approximately 1800 miles thick. The asthenosphere which is found within the upper mantle. The lithosphere and the crust may appear to be the same but they are not. The crust’s base is defined by the Mohorovicic discontinuity, while the lithosphere is the rigid part that is consists of the crust (continental and oceanic) and part of the upper mantle. The asthenosphere is of plastic consistency and extends deeper into the earth for about 400 miles and it rests on top of more dense inner mantle. It is as a result of the mantle convection process that geological processes like continental drifts and volcanic activity are possible.

Eventually, the final layer of the earth is reached, which is the core located approximately 1,800 to 3900 beneath the earth’s surface. It is comprised of the outer and the inner core. The average core temperature is between 4000 degrees Fahrenheit at the top layers and increases as you go toward the center of the earth to a maximum of about 9000 degrees Fahrenheit.

Within the outer core, the metals found at this depth are molten liquid. The earth’s rotation that moves the outer core fluid like consistency results in the creation of earth’s magnetic fields. The inner core is the final layer that makes the earth and is located 3,219 miles beneath the crust and it is 800 miles thick. The geologists estimate the pressure at this depth is the equivalent of 3,000,000 times the air pressure that would be experienced at sea level. It is as a result of the depth and intense pressure that the pure iron found at this depth is solid and is suspended within the outer core fluid.

In conclusion, the Earth’s geological evolutionary process is still ongoing. Though the layers are still perhaps going to remain the same for several millions of years to come one  thing that is for sure is the geological process that shape the continents and the oceans are ever ongoing. Perhaps the landscape that exists thousands or millions of years from now would be totally different from what is seen today.

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