Layers of Earth: The Crust, the Mantle and the Core for NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc. 2023
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Layers Of Earth: The Crust, The Mantle and The Core (Environmental Science)
The Crust
Thickness of crust
- Oceanic areas – 5 - 10 Km (More Iron)
- Continental areas – 35 Km (Less Iron)
- Orogenic belts- 55 - 70 Km
Density of crust is 2.6 - 3 gm⟋cm3
- Sub-divisions of crust:
- Sial- Al and Silica
- Sima- Mg and Silica
Conrad Discontinuity- Separates Sial layer from the underlying Sima layer
The Mantle
- Thickness is about 2865 km
- Density of mantle is 3 gm⟋cm3
- Temperature of upper mantle is 870°C and lower mantle is upto 4470°C
- Upper mantle has pyrolite (3 parts of ultramafic rock + 1 part of Basalt) .
- Lower Mantle extends from 1000 Km to the core boundary.
- Repetiti Discontinuity- At 950 Km depth- It marks the lower limit of the very rapid rise in the velocity of seismic vibrations.
The Core
- Thickness of 3500 Km
- Density is 9 – 12 gm⟋cm3
- Consists of three parts:
- Outer Core- Homogeneous fluid
- Middle Core- transition layer
- Inner Core- metallic Ni and Fe
Facts
- Central Temperature of core- 6000°C
- Central Pressure of core- 392 × 108 bars
- Density of centre of core- 18gm⟋cm3
- Core is separated from the Mantle by the Guttenberg Weichert Discontinuity
- Mohorovicic Discontinuity- This Boundary separates crust (low density silicates) from mantle (high density silicates) .
Multiple Choice Questions
1. Which among the following discontinuity separates the Sial layer from Sima layer?
- Conrad Discontinuity
- Mohorovicic Discontinuity
- Repetiti Discontinuity
- None of the above
Answer: a
2. Metallic Iron and Nickel is found at
- Inner core
- Crust
- Mantle
- Earth՚s surface
Answer: a
3. Central temperature of the core is
- 2000°C
- 4000°C
- 5000°C
- 6000°C
Answer: d
4. Which among the following statement is true?
- Mantle is the upper region of lithosphere
- Inner core is the transition layer
- Oceanic crust is denser than continental crust
- All of the above
Answer: c
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