Mechanically: Asthenosphere, mesospheric mantle, outer core, and the inner core.
Chemically: Crust, upper mantle, lower mantle, outer core, and inner core.
1. Continental crust (25-40 km?)
2. Oceanic crust (~6 km)
1. Upper mantle (650 km)
2. Lower mantle (2235 km)
1. Outer core: liquid (2270 km)
2. Inner core: solid (1216 km)
- It is the outermost solid part of the earth, normally about 8-40 kms thick.
- Nearly 1% of the earth’s volume and 0.5% of earth’s mass are made of the crust.
- The thin parts are the oceanic crust, which underlie the ocean basins (5–10 km) and are composed of dense (mafic) iron magnesium silicate igneous rocks, like basalt.
- The thicker crust is continental crust, which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks, like granite.
- The uppermost mantle together with the crust constitutes the lithosphere.
- The crust-mantle boundary occurs as two physically different events.
- First, there is a discontinuity in the seismic velocity, which is most commonly known as the Mohorovičić discontinuity or Moho.
- Second, in oceanic crust, there is a chemical discontinuity between ultramafic cumulates and tectonized harzburgites.
- The mean density of the materials in the crust is 3g/cm3.
- The discontinuity between the hydrosphere and crust is termed as the Conrad Discontinuity.
- The portion of the interior beyond the crust is called as the mantle.
- The mantle is about 2900kms in thickness.
- The upper and lower mantle are separated by the transition zone.
- The lowest part of the mantle next to the core-mantle boundary is known as the D″
- The mantle is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust.
- Nearly 84% of the earth’s volume and 67% of the earth’s mass is occupied by the mantle.
- The major constituent elements of the mantle are Silicon and Magnesium and hence it is also termed as SIMA.
- The density of the layer is higher than the crust and varies from 3.3 – 5.4g/cm3.
- Convection of the mantle is expressed at the surface through the motions of tectonic plates.
- The asthenosphere (in between 80-200km) is a highly viscous, mechanically weak and ductile, deforming region of the upper mantle which lies just below the lithosphere.
- The asthenosphere is the main source of magma and it is the layer over which the lithospheric plates/ continental plates move (plate tectonics).
- The discontinuity between the upper mantle and the lower mantle is known as Repetti Discontinuity.
- The portion of the mantle which is just below the lithosphere and asthenosphere, but above the core is called as Mesosphere.
- It is the innermost layer surrounding the earth’s centre.
- The inner core was discovered in 1936 by Inge Lehmann and is generally believed to be composed primarily of iron (Fe) and nickel (Ni) and hence it is also called as NIFE.
- The core is separated from the mantle by Guttenberg’s Discontinuity.
- The core constitutes nearly 15% of earth’s volume and 32.5% of earth’s mass.
- The core is the densest layer of the earth with its density ranges between 9.5-14.5g/cm3.
- The Core consists of two sub-layers: the inner core and the outer core.
- The inner core is in solid state and the outer core is in the liquid state (or semi-liquid).
- The discontinuity between the upper core and the lower core is called as Lehmann Discontinuity.
- Barysphere is sometimes used to refer the core of the earth or sometimes the whole interior.