THAR DESERT

The Thar Desert Rajasthan: थार मरुधर, Hindi: थार मरुस्थल, Sindhi: ٿر ريگستان, Urdu: صحراےَ تھر also known as the Great Indian Desert is a large, arid region in the northwestern part of the Indian subcontinent and forms a natural boundary running along the border between India and Pakistan. With an area of more than 259,000 km2 (100,000 sq mi), within the Indian state of Rajasthan, covering the districts of Jaisalmer, Barmer, Bikaner and Jodhpur, and some region of the states of Punjab, Haryana and Gujarat. It is the world's 9th largest subtropical desert.

Location and description;

Thar Desert extends from the Sutlej River, surrounded by the Aravalli Ranges on the east, on the south by the salt marsh known as the Great Rann of Kutch parts of which are sometimes included in the Thar, and on the west by the Indus River. Its boundary to the large thorny steppe to the north is ill-defined. It lies mostly in the Indian state of Rajasthan, and extends into the southern portion of Haryana and Punjab states and into northern Gujarat state.

Physiography and geology;

The Thar Desert slopes imperceptibly towards the Indus Plain and surface unevenness is mainly due to sand dunes. The dunes in the south are higher, rising sometimes to 152 m whereas in the north they are lower and rise to 16 m above the ground level.

The Aravalli forms the main landmark to the south-east of Thar Desert.

Desert soil - The soils of the Arid Zone are generally sandy to sandy-loam in texture. The consistency and depth vary according to the topographical features. The low-lying loams are heavier and may have a hard pan. Some of these soils contain a high percentage of soluble salts in the lower horizons, turning water in the wells poisonous.

Origin;

The origin of the Thar Desert is a controversial subject. Some consider it to be 4000 to 10,000 years old, whereas others state that aridity started in this region much earlier. Another theory states that area turned to desert relatively recently: perhaps around 2000 - 1500 BC. Around this time the Ghaggar-Hakra ceased to be a major river. It now terminates in the desert but at one time was a water source for the Indus Valley Civilization centre of Mohenjo-daro. It has been observed through remote sensing techniques that Late Quaternary climatic changes and neotectonics have played a significant role in modifying the drainage courses in this part and a large number of palaeochannels exist.

Most studies did not share the opinion that the palaeochannels of the Sarasvati River coincide with the bed of the present-day Ghaggar and believe that the Sutlej along with the Yamuna once flowed into the present riverbed. It has been postulated that the Sutlej was the main tributary of the Ghaggar and that subsequently the tectonic movements might have forced the Sutlej westwards, the Yamuna eastwards and thus dried up the Ghaggar-Hakra.

Studies on Kalibangan in the desert region by Robert Raikes indicate that it was abandoned because the river dried up. Prof. B. B. Lal retd. Director General of Archaeological Survey of India) supports this view by asserting: "Radiocarbon dating indicates that the Mature Harappan settlement at Kalibangan had to be abandoned around 2000-1900 BCE. And, as the hydrological evidence indicates, this abandonment took place on account of the drying up of the Ghaggar-Hakra. This latter part is duly established by the work of Raikes, an Italian hydrologist, and of his Indian collaborators".