The asthenosphere is a mechanically weak layer beneath which part of Earth? It is characterised by low seismic wave velocities and high attenuation.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. Lithosphere.
- The asthenosphere is a partially molten, ductile, and mechanically weak layer of the upper mantle situated directly beneath the lithosphere.
- This layer allows the rigid tectonic plates of the lithosphere to move and "float" on top of it. Its characteristic low seismic wave velocities and high attenuation are due to its higher temperature and partial melting, which make it less rigid than the layers above and below.
Other Options:
- Exosphere, Ionosphere, and Troposphere are layers of Earth's atmosphere, not its solid interior structure.
- The troposphere is the lowest atmospheric layer, the ionosphere is a part of the upper atmosphere, and the exosphere is the outermost layer of the atmosphere.