Consider the statement about Mantle
- It extends from Repetti discontinuity to a depth of 3,900 km.
- The lower mantle extends beyond the asthenosphere and it is in a liquid state.
- Temperatures range from approximately 200 °C at the upper boundary with the crust to approximately 4,000 °C at the core-mantle boundary.
Correct options are:
- Only 2
- Only 3
- Only 1
- Only 1,3
Answer: ( b ) Only 3
- Mantle forms about 83 per cent of the earth’s volume and holds 67% of the earth’s mass.
Statement 1 is incorrect;
It extends from Moho’s discontinuity to a depth of 2,900 km.
- The density of the upper mantle varies between 2.9 g/cm3 and 3.3 g/cm3.
- The density ranges from 3.3 g/cm3 to 5.7 g/cm3 in the lower mantle.
- The mantle is composed of silicate rocks that are rich in iron.
- Regarding its constituent elements, the mantle is made up of 45% oxygen, 21% silicon, and 23% magnesium (OSM).
- Because of the temperature difference, there is a convective material circulation in the mantle (although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile).
Statement 2 is incorrect;
The lower mantle extends beyond the asthenosphere. It is in a solid state.
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Statement 3 is correct
Temperatures range from approximately 200 °C at the upper boundary with the crust to approximately 4,000 °C at the core-mantle boundary.
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