Geology And Geophysics

Structures of the Earth



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Geophysical studies have revealed that the interior of the Earth is comprised of multiple layers, just like the exterior. These layers, more commonly known as structures, of the earth can be defined in two ways, chemically and mechanically. Chemically, the layers can be divided into crust, upper mantle, lower mantle, outer core, and inner core. Both the crust and the outermost layer of upper mantle share the same mechanics, solid and rigid, therefore both of them are mechanically classified as lithosphere. Below it, the rest of upper and lower mantle are classified as asthenosphere. This article will explain about the characteristics and depth of each layer.

Crust – The crust is the very ground that we stepped on, and also the outermost layer of the Earth. The Earth’s crust can be distinguished into two parts, the continental crust and the oceanic crust. Continental trust, which ranges from 30-40 km in depth, is composed of granite rocks, while the oceanic crust, which is about 5km in depth, is mainly composed of basalt rocks.

Upper Mantle – While the outermost upper mantle belongs to the Lithosphere, a large part of it is not solid; in fact, they are somewhat viscous, and are capable of moving the tectonic plates around the world. These viscous parts of the upper mantle, constitutes the asthenosphere, together with lower mantle. The upper mantle ranged from 40-400km in depth, and mainly comprised of ferro-magnesium silicates.

Lower Mantle – The lower mantle is composed of a very viscous substance, allowing the tectonic plates to “float” above it. Scientists believe that this flowing movement is caused by convection currents, which is a current that is born from the temperature difference inside the mantle, enabling the hotter part of the mantle to arise and replace the cooler part of the mantle, which sinks due to gravity.

Outer Core – The outer core is like a sea of very hot metals. It was so hot that all metals in this region are all in liquid state. It is composed mainly of nickel-iron alloy, and its thickness is around 2300 km.

Inner Core – The inner core is the opposite of the outer core, it is very solid and composed almost entirely of iron. The pressure and temperature of this area are so great that the metals are squeezed together and are not able to move freely like a liquid. The inner core is 1200km thick, and some scientists believe that it has some correlation that causes the Earth’s magnetic field. 

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