The Thar Desert (Hindi: थार मरुस्थल), also known as the Great Indian Desert, is an arid region in the north-western part of the Indian subcontinent that covers an area of in India and Pakistan. It is the world's 20th-largest desert, and the world's 9th-largest hot subtropical desert. About 90% of the Thar Desert is in India, and about 10% is in Pakistan. The Thar Desert is about 5.12% of the total geographical area of India. More than 55% of the desert lies in the Indian state of Rajasthan; the portion in India also extends into Gujarat, Punjab, and Haryana. The portion in Pakistan extends into the provinces of Sindh and Punjab (the portion in the latter province is referred to as the Cholistan Desert). The Indo-Gangetic Plain lies to the north, west and northeast of the Thar desert, the Rann of Kutch lies to its south, and the Aravali Range borders the desert to the east. History of desertification Ice-age desertification During the Last Glacial Maximum 20,000 before present, an approximately ice sheet covered the Tibetan Plateau, causing excessive radiative forcing i.e. the ice in Tibet reflected at least four times more radiation energy per unit area into space than ice at higher latitudes, which further cooled overlying atmosphere at that time. This impacted the regional climate. Without the thermal low pressure caused by the heating, there was no monsoon over the Indian subcontinent. This lack of monsoon caused extensive rainfall over the Sahara, expansion of the Thar Desert, more dust deposited into the Arabian Sea, a lowering of the biotic life zones on the Indian subcontinent, and animals responded to this shift in climate with the Javan rusa deer migrating into India. Desertification due to drying up of Sarasvati river 10,000-8,000 years ago a paleo channel of Ghaggar-Hakra River - identified with the paleo Sarasvati River, after confluence with Sutlej flowed into the Nara river - a delta channel of the Indus River, changed its course, leaving the Ghaggar-Hakra as a system of monsoon-fed rivers which did not reach the sea and now ends in the Thar desert. Around 5,000 years ago when the monsoons that fed the rivers diminished further, the Indus Valley Civilisation (IVC) prospered in this area, with the rise of numerous IVC urban sites at Kalibangan (Rajasthan), Banawali and Rakhigarhi (Haryana), Dholavira and Lothal (Gujarat) along this course. 4,000 years ago when monsoons diminished even