Question

The Asthenosphere is a part of :

• A. The Crust
• B. The Upper Mantle
• C. The Core
• D. The Lower Mantle

Answer 1

Answer:

B. The Upper Mantle

Earth's Interior Layers

• The Asthenosphere: It is a highly viscous, mechanically weak, and ductile region of the Earth's upper mantle. It lies just below the lithosphere.

• Depth and Location: It typically begins at a depth of about 80 to 100 km and extends to approximately 700 km below the Earth's surface.

• Physical Properties: The material here is in a semi-molten state due to high temperatures and pressures, which allows it to behave plastically. It is the zone where convection currents occur.

• Geological Significance: The movement of tectonic plates, which make up the rigid Lithosphere, is facilitated by the plastic, flowing nature of the asthenosphere beneath them.

Key Comparisons:

• Lithosphere: The rigid, outermost shell of the Earth, consisting of the crust and the uppermost part of the mantle.

• Asthenosphere: The ductile, flowing layer immediately beneath the lithosphere.

• Mesosphere: The section of the mantle below the asthenosphere, extending to the core-mantle boundary (the Gutenberg discontinuity).

• Scientific Terminology: The term astheno comes from the Greek word meaning 'without strength', reflecting its ability to deform rather than fracture under stress.