Advertisement

Terrestrial mantle

Advertisement

The mantle is a particular type of layer within an astronomical body . A mantle in most cases occurs in a solid object as the layer of material that surrounds a definable and extra dense core . The mantle itself can be divided into two sub-layers and can be covered by a layer called the crust , as is the case on our planet Earth. In the interior of the Earth, the mantle is a rocky layer that is found directly under the crust and on the outer core . The Earth’s mantleIt makes up about 70 percent of the Earth’s volume and overlaps the Earth’s iron-rich core, which occupies about 30 percent of the Earth’s volume. Although predominantly solid , much of the mantle is highly viscous due to the extremely high pressures within it. The convection of the mantle is expressed on the surface through the movements of the tectonic plates .

Advertisement

What is the Earth’s mantle?

The Earth’s mantle is the intermediate structure located in the geosphere and is the limit between the crust and the Earth’s core . It is between the Mohorovicic discontinuity and the Gutenberg discontinuity .

Advertisement
  • Characteristics of the land cover
  • Composition
  • Layers of the Earth’s mantle
  • Importance of the terrestrial mantle

Characteristics of the land cover

Among the main characteristics of the terrestrial mantle we can mention the following:

Advertisement
  • The mantle is distinguished from the crust by chemistry , rock types , rheology, and seismic characteristics .
  • The melting part of the material of the mantle makes incompatible elements separate from the rock mantle, with less dense material that float up through the cracks or fissures, chilled and frozen on the surface
  • Typical mantle rocks have a higher magnesium to iron ratio and a smaller portion of silicon and aluminum than the crust.
  • The mantle rock less than 400 km deep consists mainly of olivine , pyroxenes, spinel and garnet.
  • Below 650 km, all the minerals in the upper mantle begin to become
  • The upper part of the mantle is defined by a sudden increase in seismic velocity.
  • The upper mantle plus the overlying crust are relatively rigid and form the lithosphere .
  • Beneath the lithosphere, the upper mantle becomes noticeably more plastic in its rheology.
  • Very little is known about the lower mantle, other than that it appears to be seismically homogeneous.

Composition

Its composition has not yet been determined exactly, but it can be said that it is composed of:

  • 46% silicon oxide
  • 38% magnesium oxide
  • 8% iron oxide

The speed of the seismic waves that occur in the mantle makes the density of the materials that make it up higher. The mantle materials are also rich in mafic minerals and iron , mainly olivine and pyroxene. You can also find rocks such as peridotite , dunite and eclogite , which have high percentages of iron and magnesium. The materials in the mantle are in a solid state or in a viscous form due to pressures. Its viscosity is approximately 1021 and 1024 Pascals depending on how deep it is.

Layers of the Earth’s mantle

One of the layers of the earth’s mantle is viscous and the other is rigid, this causes an acceleration in seismic waves between both layers . Geologists have differentiated the following layers in the Earth’s mantle:

  • Upper mantle : this layer begins in the area known as Moho and covers approximately 400 kilometers deep. It is made up of peridotite rocks and its density is 3.3 g / cm3. It is solid and viscous . In the upper mantle we can find the asthenosphere, which is responsible for marking the areas of partial fusion. The density of the upper mantle is 3.4 and 4.6.
  • Transition zone : it is the intermediate layer that is between the upper mantle and the lower mantle. Its thickness is 300 kilometers and the exact way in which the materials in it are created is not known. This zone has several convection currents .
  • Lower mantle : it is the layer of the earth’s mantle located between 700 and 2900 kilometers deep. The materials found in it are dense and with abundant iron and magnesium oxide . It is a mantle with fluid and viscous characteristics . No major changes occur in this layer, but gradients do occur in the speed of seismic wave propagation.

Importance of the terrestrial mantle

The terrestrial mantle is important because it forms the inner layer of the earth richest in heavy elements and is always in constant motion , which allows the tectonic plates to move, thus allowing the evolution of the earth. The mantle together with the outer core produces a magnetic field that protects the earth against powerful radiation and at the same time forms the northern lights that can be observed at the poles.

Leave a Comment