The planet can be divided into four main layers: the solid crust on the outside, the mantle, the external core and the inner core. Out of them, the mantle is the thickest layer, while the late is the thinnest layer.

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byMihai Andrei

The earth can be split into 4 main layers: the solid late on the outside, the mantle, the outer core and also the inside core. Out of them, the mantle is the thickest layer, if the late is the thinnest layer.

The earth structure

Artistic depiction of the Earth’s structure. Picture via Victoria Museum.

The Earth’s structure can be characterized in number of ways, yet general, we view the earth as having actually a hard crust top top the outside, an inner and also an outer core, and also the mantle in between. The crust’s thickness varies between some 10 km and just end 70 km, having an median of around 40 km. The main point has, in total, a radius that 3500 km, but it is typically viewed as two unique parts:

the solid inner core, with a radius the 1220 kmthe viscous external core, v a radius the 2300 km

The mantle’s thickness is around 2900 kilometres – so if you think about the Earth’s main point as one large thing, then the main point is the “thickest layer” (though has actually a enlarge radius is probably a far better way of saying it) – yet the idea the a different outer and inner core is normally accepted.


The Mantle – thickness and also composition

The mantlecomprises around 83% of the Earth’s volume. That is divided into number of layers, based upon different seismological characteristics (as a matter of fact, lot of what us know about the mantle comes from seismological information – more on that later in the article). The upper mantle expand from where the crust end to about 670 km. Also though this area is pertained to as viscous, girlfriend can also consider it as developed from absent – a rock called peridotite come be an ext precise.A peridotite is a dense, coarse-grained igneous rock, consistingmostly that olivine and pyroxene, two minerals only found in igneous rocks.

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Peridotite, as viewed on the Earth’s surface. Picture via Pittsburgh University.

But it it s okay even an ext complicated. The late is separated into tectonics plates, and those tectonic plates are actually thicker than the tardy itself, encompassing the top component of the mantle. The crust and also that top component of the mantle (going00 come 200 kilometers below surface, is called the asthenosphere. Clinical studies imply that this layer has physical properties the are different from the rest of the upper mantle. Namely, the rocks in this component of the mantleare much more rigid and brittle since of cooler temperatures and also lower pressures.

Below that, there is the lower mantle – varying from670 come 2900 kilometers listed below the Earth’s surface. This is the area with the greatest temperatures and also biggest pressures, reaching all the method to the external core.


Mantle Trivia: even though girlfriend can consider the mantle together molten rock or magma, modern-day research found that the mantle has between 1 and 3 times much more water 보다 all the seas on planet combined.


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How have the right to we study the mantle?

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Waves propagating from Earthquakes through the Earth. Photo via Brisith geology Survey.

Pretty lot all the valuable geology we execute takes areas at the crust. Every the rock analysis, the drilling… whatever we do is excellent in the crust. The deepest drill ever before is part 12 km listed below the surface… so climate how deserve to we understand the mantle?

As I said earlier, many of what we know around the mantle originates from seismological studies. When huge earthquakes take place, the waves propagate transparent the Earth, carrying with them information from the layers they pass through – consisting of the mantle. Furthermore, modern simulations in the rap showed just how minerals likely behave in ~ those temperatures and pressures, and we also have indirect gravitational and magnetic information, and studies on magma and crystals found on the surface. Yet the mass of the information originates from seismic analysis.

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Image via Wiki Commons.

Seismic waves, as with light waves, reflect, refract and also diffract once they accomplish a border – that’s just how we know where the late ends and also where the mantle begins, and also the very same goes because that the mantle and also the core. The waves also behave differently relying on different properties, such together density and also temperature.

In the mantle, temperatures selection between 500 to 900 °C (932 to 1,652 °F) in ~ the top boundary with the crust; to over 4,000 °C (7,230 °F) in ~ the boundary with the core. Many thanks to the substantial temperatures and also pressures in ~ the mantle, the rocks within undergo slow, viscous choose transformations over there is a convective product circulation in the mantle. How material flows in the direction of the surface ar (because it is hotter, and also therefore less dense) when cooler product goes down. Many think that this convection actually is the main driver behind key tectonics.

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Mantle convection may be the main driver behind key tectonics. Photo via college of Sydney.

Another exciting fact around the mantle: Earthquakes in ~ the surfaceare a an outcome of stick-slip faulting; rocks in the mantle can’t error though, yet they sometimes generate comparable earthquakes. It’s not clear why this happens, yet several mechanisms have actually been proposed, includingdehydration, thermal runaway, and also mineral phase change. This is just a reminder that how tiny we tho know around our planet: we’ve just scratched the surface ar of the thinnest layer, the crust.

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Mihai Andrei

Andrei"s background is in geophysics, and he"s to be fascinated by it ever since he was a child. Emotion that over there is a gap between scientists and the basic audience, he began ZME scientific research -- and also the results are what you view today.