Which one of the following best describes the Lithosphere ?

The lithosphere is the rigid, outermost mechanical layer of the Earth [1]. It is defined by its physical properties as a brittle solid that moves as a single unit over the more plastic and deformable asthenosphere [1]. Structurally, the lithosphere consists of the entire crust (both continental and oceanic) and the uppermost portion of the mantle [3][4]. Its thickness typically ranges from approximately 10 km at mid-ocean ridges to over 200 km beneath stable continental interiors [1][3]. While the crust and mantle are chemically distinct layers, the lithosphere combines the crust and the rigid part of the upper mantle into one mechanical layer [2][5]. This layer is broken into tectonic plates, which float and move upon the semi-molten asthenosphere below [3]. Therefore, the lithosphere is best described as the combination of the crust and the upper mantle.

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Lithosphere > p. 10
2. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > Lithosphere > p. 54
3. [4] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > The Mantle > p. 23
4. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > 4.1. The Internal Structure of The Earth > p. 52
5. [5] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > Asthenosphere > p. 55