Prelims 5010

Consider the following statements regarding Asthenosphere:
1. Asthenosphere lies below lithosphere.
2. Asthenosphere is highly viscous.
Which of the statement(s) given above is/are correct?
1 only
2 only
Both 1 and 2
Neither 1 nor 2
Explanation :
The lithosphere is the solid, outer part of the Earth. The lithosphere includes the brittle upper portion of the mantle and the crust, the outermost layers of Earth’s structure. It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below. The asthenosphere is the highly viscous, mechanically weak deforming region of the upper mantle of the Earth. It lies below the lithosphere, at depths between approximately 80 and 200 km (50 and 120 miles) below the surface. The Lithosphere-Asthenosphere boundary is usually referred to as LAB.