The Earth is made up of four primary layers that exist in a spherical structure resembling an onion. The four layers have distinct physical and chemical properties that are influenced by their position from the Earth’s surface. The layers are the crust, mantle, inner core and outer core. These layers have both a direct and indirect impact on the Earth's surface. A boundary known as the Mohorovicic (or simply Moho) discontinuity can be found in between the crust and the mantle.
5. Inner core
The inner core is the central layer of the Earth, composed of dense materials that are thought to have accumulated during the formation of the Earth. Unlike the outer core, the inner core exists in a solid form due to the increased pressure which solidifies iron in the layer. The core has a radius of 750 miles. Temperatures within the core can reach over 10,000 Fahrenheit and the layer contains mostly iron and nickel elements with heavier mineral deposits of gold, silver, platinum, palladium and tungsten.
4. Outer core
The outer core is a liquid layer that has a width of 1,430 miles and a depth of 2,100 miles. Temperatures can reach 10,345 Fahrenheit which is hot enough to melt the iron that composes the layer. The outer core has a very high velocity, spinning at rates higher than the rate of the Earth resulting in the formation of the Earth’s magnetic field.
3. Lower mantle
The lower mantle is larger than the upper mantle and it reaches a depth of 400-1,800 miles. When compared to the upper mantle, the lower mantle is less dense and is mostly solid due to high temperature and pressure. Little information is known about the lower mantle.
2. Upeer mantle
The upper mantle is the second layer below the crust with materials existing in a semi-molten to solid state. The mantle has convectional currents within it which are responsible for tectonic movements of the Earth's crust, seafloor spreading, mountain formation, and temperature regulation. Scientists believe that these movements were instrumental in the formation of the Earth's crust. Temperature and pressure within the mantle increase with depth. The mantle is divided into two layers. The upper mantle is separated from the crust by the Mohorovicic discontinuity or Moho. It extends to a depth of 200-250 miles from the crust. Most of the materials in the upper mantle exist in a semi-molten state (magma) and are brought to the Earth's surface through tectonic movements such as volcanicity. The pressure in the upper mantle is responsible for different chemical and physical properties. Rocks in the upper mantle have less silicon and more iron and magnesium than those of the crust.
The crust is the uppermost and thinnest layer of the Earth made up of mainly sial (silica and aluminium) and sima rocks. The crust extends to a minimum depth of 3.1 miles and a maximum depth of 43.5 miles. The crust has two different varities: the continental crust and oceanic crust. The continental crust supports the solid land mass we live on and is less dense and thicker than the oceanic crust. It also has a higher level of elevation due to its low density and impact from seismic waves. The oceanic crust supports oceans and is composed of dense rocks such as magnesium and silicate igneous rocks. In areas where the continental crust meets the oceanic crust, the physical and chemical properties of the two become similar.
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