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Top 10 Facts About The Earth’s Mantle

The Earth just like the other terrestrial planets has multiple layers which are the crust, mantle, outer core, and inner core. Each layer has its impact on life on Earth’s surface. The mantle of the Earth is a stratum of silicate rock that exists between the crust and the outer core. It has a mass of 4.01 1024 kg and thus accounts for 67% of Earth’s bulk. The mantle starts at the Mohorovicic discontinuity and extends down to the core-mantle boundary, also known as the Gutenberg discontinuity. It has a thickness of 2,900 kilometers and accounts for approximately 84% of the Earth’s capacity. It is primarily solid, but on geologic time scales it behaves as a viscous fluid with the consistency of caramel. Here are some of the facts about Earth’s mantle.

Read also; Top 10 Facts About The Earth’s Outer Core

1. The mantle rock lies between the crust and the outer core

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The Earth consists of three distinct layers the inner core, the outer core, the mantle, and the crust. The mantle in particular is the main solid interior of the Earth. It is the layer of Earth between its dense super-heated core and its thin outer layer, the crust. The mantle can be up to 2900 km deep beneath the crust. It is made up of heated, compact solid rock that is rich in iron and magnesium.

2. The mantle consists of the majority of Earth’s volume

The Mantle is the Earth’s thickest layer. The intermediate mantle is 1800 miles thick and comprised of highly heated solid rock that flows like asphalt under tremendous weight. Although the core and mantle are roughly similar in thickness, the core accounts for only 15% of the Earth’s volume, while the mantle accounts for 84%, with the crust accounting for the remaining 1%.

3. The mantle is divided into several layers

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Seismology results have led to the division of the mantle into sections. These are the upper mantle, which reaches a depth of 410 km from the surface, the transition zone which reaches a depth of 410 km, the lower mantle, which reaches a depth of 2,891 km, and the core-mantle boundary which has a variable thickness (200 km or 120 mi on average). There are two major zones in the upper mantle. The innermost of these is the asthenosphere, which is made up of plastic flowing rock with a thickness of around 200 km. The outer zone is the lithosphere’s lowermost layer, which is formed of unyielding rock and is 50 to 120 km thick. The Earth’s crust is the upper component of the lithosphere, a thin layer 5 to 75 km thick that is separated from the mantle by the Mohorovicic discontinuity (or “Moho,” which is defined by a rapid rise in the speed of seismic waves downhill).

4. The mantle is extremely hot

Temperatures in the mantle range from around 500 K at the upper border with the crust to about 4,200 K at the core-mantle barrier. The temperature of the mantle rises fast in the thermal boundary layers at the top and bottom of the mantle and gradually rises throughout the interior. Despite the fact that the higher temperatures significantly exceed the melting points of the mantle rocks at the surface (about 1,500 K for representative peridotite), the mantle is almost entirely solid. Because the temperature at which melting begins (the solidus) increases with pressure, the huge lithostatic pressure exerted on the mantle prevents melting.  At the core-mantle barrier, pressure in the mantle rises from a few hundred megapascals at the Moho to 139 gigapascals (20,200,000 psi).

5. The Mantle is made up of various mineral components

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The rocks that makeup Earth’s mantle are largely silicates and are a diverse group of substances with a silicon, and oxygen structure. Olivine, garnet, and pyroxene are common silicates found in the mantle. Magnesium oxide is the other major form of rock found in the mantle. Iron, aluminum, calcium, sodium, and potassium are also mantle elements. Silicon dioxide (SiO2) is the most common at 48%, followed by Magnesium Oxide (MgO) at 37.8%. Olivine, pyroxenes, spinel, and garnet are examples of rocks found inside the mantle.

Read also; 15 Fun Facts about Earth

6. The majority of mantle research is carried out by monitoring seismic waves

Humans do not have direct access to samples of the Earth’s interior deeper than the upper mantle. Attempts to dig through the crust to reach the mantle have been futile. Given the scarcity of genuine earth fragments deeper than the asthenosphere, how do we know about the earth’s innermost layers, what they are comprised of, and what their qualities and processes are? The energy released by earthquakes travels in waves. Seismology is the study of seismic waves. Seismologists study seismic waves to learn about earthquakes and the Earth’s innards. Looking at seismic waves is one clever way scientists learn about the Earth’s mantle. Seismic waves travel in all directions from the point where the ground breaches and are detected by seismographs all around the planet.

7. The mantle plays a vital role in the crust evolution

The Earth’s mantle is vital in the formation of the crust and supplies driving forces for plate tectonics which determines the planet’s habitability. It is crucial in the formation of the crust because it provides thermal and mechanical driving factors for plate tectonics. The heat released by the core is transmitted to the mantle where it is convected through the mantle to the lithosphere’s base. Mantle plumes created near the core-mantle boundary layer may transport the remainder upward. Seismology’s resolution of mantle structures has considerably improved over the last decade. The mantle is also a graveyard for falling lithospheric slabs.

8. Mantle plumes are caused by heat transmission between mantle layers

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What is a mantle plume? A mantle plume is a superheated rock upwelling from the mantle. Mantle plumes are the most likely cause of “hot spots,” which are volcanic zones that are not formed by plate tectonics. A mantle plume melts into a diapir as it reaches the upper mantle. This molten material causes volcanic eruptions by heating the asthenosphere and lithosphere. The Hawaiian hot spot, located in the middle of the North Pacific, is thought to be above a mantle plume since it remains relatively constant as the Pacific plate travels northwesterly. Geologists believe this has enabled the Hawaiian hot spot to form a chain of volcanoes.

Read also; 15 Fascinating Facts about Volcanoes

9. The mantle is a mixture of solid and liquid

The pressure at the mantle’s bottom is 136 GPa (1.4 million atm). Because the material beneath must sustain the weight of everything above it, pressure rises as depth increases. The Mantle is in liquid and solid form although, in long timescales, the entire mantle is assumed to deform like a fluid, with persistent plastic deformation accommodated by the passage of point, line, and/or plane defects through the solid crystals that compose the mantle. The upper mantle viscosity is estimated to be between 1019 and 1024 Pas, depending on depth, temperature, composition, degree of stress, and a variety of other parameters. As a result, the upper mantle can only move very slowly.

10. The mantle-crust border does not exist at a constant depth

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The Mohorovicic discontinuity (the Moho), which marks the transition between the mantle and crust, does not occur at a constant depth in the lithosphere. The concept of isostasy explains how the crust can “float” on top of the more pliable mantle due to variations in the physical, chemical, and mechanical properties of the two layers. Not every area of the Earth is in isostatic equilibrium. The density, thickness, and dynamic forces at play in the mantle all affect the isostatic balance.

The thermal and mechanical driving factors for plate tectonics are provided by the mantle which also plays a significant role in the evolution of the crust.