What Lies Beneath: The Earth's Hidden Secrets


“What Lies Beneath” may imply we are discussing a horror movie with the same title; however, this article takes you to a journey into the center of the Earth and above. It is not about Jules Verne’s famous novel, Journey to the Center of the Earth, either; in this journey, we will dig deep into Earth’s layers to find out what lies beneath its surface.

The Earth is made up of four layers: the crust, the mantle, the outer core, and the inner core; the inner core is the center of the Earth, and the crust is the layer we see at the top. Compared to the other layers, the crust is very thin; its thickness ranges 0–60 km, depending on the location. The thinner parts are located at the oceans, where the layer is the oceanic crust; the thickest parts include the land, where the layer is the continental crust, and where the mountains are the thickest place. The crust is made up of tectonic plates; those plates are in constant motion, either colliding with each other or moving away. Their motion explains the movement of the continents that happen over long periods of time.

The mantle lies below the crust, and it makes up to 84% of the Earth’s volume, with 2,900 km thickness. The mantle is composed of semi-molten rocks, which are called magma; they are hard at the top and soft at the bottom. The temperature of the mantle differs according to the location; at the top, the degree is 500°–900° Celsius, while at the bottom, near the core, the temperature reaches over 4000° Celsius.

The outer core is the third layer of the Earth; it is the nearest layer to the center and is extremely hot, ranging 4030°–5730°. It mainly consists of iron and nickel, and its thickness is approximately 2,300 km. The outer core is in liquid form, as it is not exposed to enough high pressure to be solidified into rocks. It is important to note that the outer core is responsible for creating the Earth’s magnetic field; the iron present in the outer core serves as a good conductor, and the motion of this liquid and the rotation of the Earth provide good energy.

The fourth and final layer of the Earth is the inner core. It resembles the outer core as it is mainly made up of iron and nickel; however, the pressure in this layer is high enough to transform the liquid into solid. The inner core is the hottest part of Earth; its temperature reaches 5500° and it is safe to say that it is as hot as the surface of the Sun. In general, when it comes to the layers of Earth, density increases at the center of the Earth—the inner core—that is why heavier elements are found.


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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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