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Difficulty: HardInternal and External Structure of the Earth

Geophysical studies reveal that Earth's internal layers are stratified according to their physical properties and chemical compositions. Arrange the following structural layers of the Earth in order of increasing average density, starting from the layer with the lowest density to the layer with the highest density.

  1. 1SIAL (Continental Crust)
  2. 2SIMA (Oceanic Crust)
  3. 3Asthenosphere (Upper Mantle)
  4. 4Lower Mantle (Mesosphere)
  5. 5Barysphere (Inner Core)

Answer

The correct sequence from lowest to highest density is: SIAL (Continental Crust) → SIMA (Oceanic Crust) → Asthenosphere (Upper Mantle) → Lower Mantle (Mesosphere) → Barysphere (Inner Core).
Earth's internal structure is naturally arranged by density due to planetary differentiation. The least dense layer at the surface is the granitic SIAL (2.7 g/cm³), followed by the basaltic SIMA (3.0 g/cm³), the semi-plastic asthenosphere in the upper mantle (3.3–3.5 g/cm³), the solid silicate lower mantle (4.5–5.7 g/cm³), and finally the ultra-dense metallic nickel-iron barysphere (12.0–13.0 g/cm³) at the center.

Step-by-Step Solution

1
Identify the chemical composition and density of the outermost continental crust.
SIAL has the lowest density (~2.7 g/cm³) due to lightweight granitic minerals (silica and aluminium).
Continental crust floats highest on the underlying layers.
2
Determine the relative position and density of the oceanic crust beneath or adjacent to SIAL.
SIMA has a higher density (~3.0 g/cm³) than SIAL because of basaltic composition (silica and magnesium).
Basaltic rocks are denser than granitic rocks.
3
Examine the mantle layers situated beneath the crust.
The asthenosphere (upper mantle) has a density of ~3.3–3.5 g/cm³, while the deeper lower mantle (mesosphere) ranges from ~4.5–5.7 g/cm³.
Density increases with depth in the mantle due to increasing pressure and heavy ultrabasic rock compositions.
4
Identify the innermost core layer density.
The barysphere (core) has the maximum density (~12.0–13.0 g/cm³).
Heavy metallic elements (nickel and iron) concentrated at the center under extreme gravitational pressure.

Key Concept

Density Stratification of Earth's Layers
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Topics

Internal and External Structure of the Earth

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