Thar Desert

The Thar Desert (), 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 18th-largest desert, and the world's 9th-largest hot subtropical desert.

About 85% of the Thar Desert is in India, and about 15% is in Pakistan. The Thar Desert is about 4.56% of the total geographical area of India. More than 60% 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.

The most recent paleontological discovery in 2023 from the Thar Desert in India, dating back to 167 million years ago, pertains to a herbivorous dinosaur group known as dicraeosaurids. This discovery marks the first of its kind to be unearthed in India and is also the oldest specimen of the group ever recorded in the global fossil record.

Geography

The northeastern part of the Thar Desert lies between the Aravalli Hills. The desert stretches to Punjab and Haryana in the north, to the Great Rann of Kutch along the coast, and to the alluvial plains of the Indus River in the west and northwest. Much of the desert area is covered by huge, shifting sand dunes that receive sediments from the alluvial plains and the coast. The sand is highly mobile due to the strong winds that rise each year before the onset of the monsoon. The Luni River is the only river in the desert. Rainfall is per year, almost all of it between June and September.

Saltwater lakes within the Thar Desert include the Sambhar, Kuchaman, Didwana, Pachpadra, and Phalodi in Rajasthan and Kharaghoda in Gujarat. These lakes receive and collect rainwater during monsoon and evaporate during the dry season. The salt comes from the weathering of rocks in the region.

Lithic tools belonging to the prehistoric Aterian culture of the Maghreb have been discovered in Middle Paleolithic deposits in the Thar Desert.

Climate

The climate is arid and subtropical. Average temperature varies with season, and extremes can range from near-freezing in the winter to more than 50 °C in the summer months. Average annual rainfall ranges from 100 to 500 mm, and occurs during the short July-to-September southwest monsoon.

The desert has both a very dry part (the Marusthali region in the west) and a semidesert part (in the east) that has fewer sand dunes and slightly more precipitation.

Desertification

During the Last Glacial Maximum, approximately 20,000 years before present, an estimated ice sheet covered the Tibetan Plateau, See chapter entitled: "Reconstruction of an approximately complete Quaternary Tibetan Inland Glaciation between the Mt. Everest and Cho Oyu Massifs and the Aksai Chin. – A new glaciogeomorphological southeast-northwest diagonal profile through Tibet and its consequences for the glacial isostasy and Ice Age cycle". significantly affecting radiative forcing; due to its low latitude, the Tibetan ice sheet reflected at least four times more solar radiation per unit area into space than ice at higher latitudes, further cooling the overlying atmosphere during that period. 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.

Between 10,000 and 8,000 years ago, a paleo channel of the Ghaggar-Hakra River – identified with the paleo Sarasvati River – after its confluence with the Sutlej flowed into the Nara river, a delta channel of the Indus River, but then changed its course. This left the Ghaggar-Hakra as a system of monsoon-fed rivers that no longer reached 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.Mythical Saraswati River
Press Information Bureau, Government of India, 20 March 2013.

By 4,000 years ago, when monsoons diminished even further, the dried-up Hakra became an intermittent river, and the urban Harappan civilisation declined, becoming localized in smaller agricultural communities.

Desertification control

The soil of the Thar Desert remains dry for much of the year, so it is prone to wind erosion. High-velocity winds blow soil from the desert, depositing some of it on neighboring fertile lands, and causing sand dunes within the desert to shift. To counteract this problem, sand dunes are stabilised by first erecting micro windbreak barriers with scrub material and then by afforestation of the treated dunes—planting the seedlings of shrubs (such as phog, senna, and castor oil plant) and trees (such as gum acacia, '' Prosopis juliflora'', and lebbek tree). The 649-km-long Indira Gandhi Canal brings fresh water to the Thar Desert. It was built to halt any spreading of the desert into fertile areas.

Protected areas

There are several protected areas in the Thar Desert:
* In India:
** The Desert National Park, in Rajasthan, covers and represents the Thar Desert ecosystem; it includes 44 villages. Its diverse fauna includes the great Indian bustard (''Chirotis nigricaps''), blackbuck, chinkara, fox, Bengal fox, wolf, and caracal. Seashells and massive fossilized tree trunks in Akal Wood Fossil Park record the geological history of the desert.
** The Tal Chhapar Sanctuary covers and is an Important Bird Area. It is located in the Churu district, from Jaipur, in the Shekhawati region of Rajasthan. This sanctuary is home to large populations of blackbuck, fox, caracal, partridge, and sand grouse.
** The Sundha Mata Conservation Reserve covers and is located in the Jalore District of Rajasthan.
* In Pakistan:
** The Nara Desert Wildlife Sanctuary covers ; it is located in is located in Mirpurkhas District. It contains the largest population of the endangered mugger crocodile in Pakistan.
** The Rann of Kutch Wildlife Sanctuary located in Badin District is an Important Bird Area and Ramsar Site