The correct option is (c).
Explanation
The Sahara Desert, the largest hot desert in the world, possesses a varied physical landscape. Contrary to popular perception, it is not a uniform expanse of sand but includes a complex mix of arid landforms such as ergs (sand seas), regs (gravel plains), and hamadas (rocky plateaus).
Statement-wise Analysis:
- Statement 1 is Incorrect. The Sahara does not consist solely of sand dunes. While sand dunes (ergs) are a prominent feature, they cover only a portion of the desert. The landscape is vast and heterogeneous, containing other significant geological formations.
- Statement 2 is Correct. A large proportion of the Sahara consists of gravel plains (regs) and elevated plateaus with bare rocky surfaces (hamadas). These surfaces are typically swept clear of sand by wind erosion, exposing the bedrock or gravel layers.
- Statement 3 is Correct. The Sahara contains several mountain ranges and high-altitude plateaus. For example, the Tibesti Mountains in Chad and the Ahaggar Mountains in Algeria feature peaks that rise well above 2500 meters. The highest peak, Emi Koussi, reaches an elevation of 3,415 meters.
Key Takeaway:
The physical geography of the Sahara is defined by a combination of ergs (sand dunes), regs (gravel plains), and hamadas (rocky plateaus), alongside significant mountain ranges, rather than being exclusively covered by sand.