Great Victoria Desert

Lore & Background

During the Last Glacial Maximum (26,000–20,000 years ago), an estimated 2,400,000 km2 ice sheet covered the Tibetan Plateau. The low latitude ice sheet reflected at least four times more solar radiation per unit area into space than ice at higher latitudes, resulting in further cooling of the overlying atmosphere. Without the thermal low pressure caused by the heating, there was no monsoon over the Indian subcontinent, which led to the deposition of dust and the desertification of the region. The upliftment of the Aravallis brought about changes in the hydrography of the region, and the Ghaggar-Hakra River system that fed the region dried up, and the region became increasingly arid. Over the years, wind blown sediments and sand from the alluvial plains and the coast accumulated in the region. The Indus Valley Civilisation had prospered in the area, with several settlements along the course of the river system. 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.

Reader's Guide

The Thar Desert is one of the most widely populated deserts in the world, with the Thar people inhabiting the area. The population is clustered into small villages, with majority of them nomadic in nature. Limited agriculture, herding of animals, and ecotourism drive the economy of the region. The natural vegetation of the region is composed of trees, thorny scrubs and scattered grasslands. The desert is home to several animal and bird species. The topography consists of sandy plains intercepted by eroded hills of low elevation. The region has a tropical desert climate with extremely hot summers and cooler winters. Majority of the rainfall is received from the southwest monsoon, which on average is less than 500 mm annually. The rainfall varies over the years, often with large spells of drought. There are very few sources of water, with the inland Luni River system being the only major river system in the region. Rain water is often stored in natural and man-made reservoirs for use in the dry season. The 649 km-long Indira Gandhi Canal, which channels water from the Indus River system, is a major source for irrigation and drinking water.

Did You Know?

• The Thar Desert is the eastern most extension of the Sahara–Arabian desert formation.
• During the Last Glacial Maximum, an estimated 2,400,000 km2 ice sheet covered the Tibetan Plateau, which reflected at least four times more solar radiation per unit area into space than ice at higher latitudes.
• The Luni River is the longest and major river in the desert, part of a minor inland river system.
• The Indira Gandhi Canal, which channels water from the Indus River system, is 649 km long and is a major source for irrigation and drinking water.
• Lithic tools belonging to the prehistoric Aterian culture of the Maghreb from the Middle Paleolithic era have been found in the Thar Desert.

Defining the Sand Sea

The Thar Desert is located in the north-western part of the Indian subcontinent stretching across the border between India and Pakistan, and is the eastern most extension of the Sahara–Arabian desert formation. It is spread across an area of 264,091 km2, with 195,091 km2 of the desert area lying in India, with the remaining in Pakistan. The desert forms about six percent of the geographical area of India, with the majority of the desert lying in the state of Rajasthan, with portions extending into Gujarat, Haryana, and Punjab. Towards the west, it extends into the provinces of Sindh and Punjab in Pakistan. The northeastern part of the Thar Desert lies between the Aravalli Hills, which separates the same from the Central highlands and the Indo-Gangetic Plain to the east. The desert stretches from the alluvial plains of the Indus River in the west and northwest, to the Great Rann of Kutch in the south.

Formation and Geographic Context

In the Mesozoic era (252 to 66 mya), the area was a low lying peneplain, covered by shallow waters. Erosion resulted in the formation of three layers of planation surfaces during the post-Mesozoic (66 to 2.6 mya), and early Pleistocene (2.6 mya to 11,000 years ago) periods. As the Himalayas arose during the mid-Miocene period (23.4 to 5.3 mya), it gave rise to the monsoon. During the Last Glacial Maximum (26,000–20,000 years ago), an estimated 2,400,000 km2 ice sheet covered the Tibetan Plateau. The low latitude ice sheet significantly affected radiative forcing, and reflected at least four times more solar radiation per unit area into space than ice at higher latitudes, resulting in further cooling of 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 region, while resulted in more dust deposited towards the Arabian Sea in the east. It also resulted in changes to the biotic life zones on the Indian subcontinent, as fauna responded to this shift in climate with species like Javan rusa deer migrating into India.

Dune Architecture and Depth

The eastern part of the Thar Desert, that lies in the western foothills of the Aravallis, consists of sandy plains intercepted by eroded hills of low elevation. It rises to about 325 m in elevations as it reaches the Aravallis, which continue as the plateau of the central India beyond the range. The sandy plains extend across to the west, with the altitude dropping to 150 m at the India-Pakistan border. Much of the desert area is covered by sand dunes that are formed due to accumulation of wind blown sand deposited over the sediments from the alluvial plains. The sand is highly mobile due to the strong winds that rise each year before the onset of the monsoon. Much of the bedrock is composed of igneous and metamorphic rocks. The geology of the region varies across its area. The oldest rocks are found in the Barmer region in the south, which are volcanic rocks composed of felsite. In the Pokhran area, there are various colored shales, with varying hardness. Pale colored sandstones composed primarily of quartz are found south of Jodhpur. Sandstones with fossils belonging to the Jurassic period (201.4 to 143.1 mya) are found to the east of Balmer, and to the east and north of Jaisalmer.

A Feature Beyond Earth

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