The Indian (Thar) Desert and the Rann of Kachchh

Detail

1. Location and extent

• The Great Indian Desert is also called the Thar Desert or Marusthali ("land of death" or "desert land"). It lies north-west of the Aravalli Range.

• The Aravallis run south-west to north-east across Rajasthan. They form the desert's eastern edge.

• Spread within India: mostly western Rajasthan, plus parts of Gujarat, Punjab and Haryana (NCERT Class 7).

• Spread outside India: the desert continues west into Sindh (Pakistan).
• Boundaries:
• East: the Aravallis.
• North: the plains of Punjab and Haryana.
• South: the Rann of Kachchh in Gujarat.
• West: the Indus plain of Pakistan.

2. Landscape: dunes and rolling land

• Undulating topography (land that rises and falls gently like waves) covered with sand.
• Longitudinal dunes: long, narrow sand ridges that run parallel to the main wind direction.

• They form where the wind blows steadily from one direction and sand supply is moderate.

• Barchans: crescent-shaped dunes (shaped like a new moon).

• Their two horns point downwind. The gentle slope faces the wind and the steep slip face lies on the sheltered side.
• They form where sand is limited and the wind blows mostly from one direction.

• Figure 2.6 in NCERT shows a barchan. A common exam question asks you to name the dune type from its shape.

• Dune height: up to 150 m (NCERT Class 7).

Feature	Longitudinal dune	Barchan
Shape	Long, straight ridge	Crescent (half-moon)
Direction compared with wind	Parallel to the wind	Horns point downwind
Sand supply	Moderate	Limited
Movement	Grows along its length	Moves forward as a whole (a shifting dune)

3. Climate and vegetation

• Rainfall: under 150 mm a year (NCERT), so the climate is arid (very dry).
• Temperature: days are very hot and nights are cold (NCERT Class 7).

• Why: dry air and bare sand let the ground heat fast by day. With no clouds to trap heat, it cools fast at night. This gives a high diurnal range of temperature (a big difference between day and night temperatures).

• Vegetation: low and sparse. It is mostly thorny bushes and hardy grasses that can survive drought.

4. Once under the sea: Mesozoic history

• The Mesozoic era (about 252–66 million years ago, the "age of dinosaurs") was a time when this region lay under the sea.
• Proof 1: Akal (Aakal) Wood Fossil Park, near Jaisalmer, Rajasthan.
• It holds fossil tree trunks about 180 million years old (Lower Jurassic).

• Petrified wood (wood turned into stone) forms like this:

  1. Trees growing near the sea were buried quickly under sediment.
  2. Water carrying silica soaked into the wood.
  3. The silica slowly replaced the wood tissue.
  4. The result is a stone copy of the tree, with its rings still visible.

• Proof 2: Brahmsar (near Jaisalmer) has marine deposits (rocks laid down on the sea floor, with remains of sea life).

• What it means: the desert is not a permanent landscape. It was sea, then coastal forest, and is now dry land.

5. Structure: Peninsular base, wind-made surface

• Underlying rock: the bedrock is part of the Peninsular Block (the old, hard and stable Gondwana landmass). So structurally the desert is a westward continuation of the Peninsula.
• Surface: it has been carved by physical (mechanical) weathering and wind.
• Physical weathering: rock breaks without changing its chemistry.
• Great heat by day makes rock expand, and cold at night makes it shrink.
• Repeated stress cracks the rock and its outer layers peel off.

• The loose pieces become sand, which the wind can carry.

• Wind-made landforms:

• Mushroom rocks (pedestal rocks): wind carrying sand blows close to the ground. The sand cuts into the base of a rock like sandpaper, but the top is above the sand's reach. The base gets thin and the top stays wide, so the rock looks like a mushroom.
• Shifting dunes: dunes that move as the wind pushes sand forward. They can bury fields, roads and villages.
• Oases: green spots where groundwater reaches the surface. In the Thar they are mostly in the south.

6. Drainage

• Slope:
• the northern part slopes towards Sindh (Pakistan);

• the southern part slopes towards the Rann of Kachchh.

• Ephemeral rivers flow only after rain and dry up for the rest of the year.

• The Luni is the main (and largest) river of the region. It is the biggest river system of Rajasthan west of the Aravallis.
• Origin: near Pushkar in the Aravallis (Ajmer district). It starts as two streams, the Saraswati and the Sabarmati, which join at Govindgarh.
• Course: it first flows west, then turns south-west.
• Mouth: it does not reach the sea. It ends in the Rann of Kachchh.

• Water: its upper course is fresh, but the lower course turns saline (salty).

• Inland drainage means streams do not reach the sea. They end in closed basins inside the desert.

• Playas are shallow, flat lake beds. They fill after rain and dry out in summer, leaving salt behind.

• Their brackish water (slightly salty water) is used to make salt.

• Sambhar Lake (Rajasthan) is India's best-known inland salt lake.

• It was designated a Ramsar site (a wetland of international importance under the Ramsar Convention, 1971) on 23 March 1990, covering 24,000 ha [3].
• It is a large saline lake fed by four streams in a shallow wetland, and its water level changes with the seasons [3].
• It supports many wintering waterbirds, including large numbers of flamingos [3].

7. Human life and water wisdom (NCERT Class 7)

• Jaisalmer, the "Golden City", gets its name from its yellow sandstone. Jaisalmer Fort is a UNESCO World Heritage Site as part of the "Hill Forts of Rajasthan".
• The Pushkar fair (Ajmer district) is a famous cattle and camel fair.
• Saving water:
• Taanka or kund is an underground tank that collects rainwater from rooftops or courtyards for drinking.
• People scour (scrub) pots with sand instead of water.

8. Changing the desert: canal irrigation and desertification

• Indira Gandhi Canal (Rajasthan Canal):
• Source: Harike Barrage in Punjab, where the Sutlej and Beas meet.
• Area served: the north-western Thar (Sri Ganganagar, Bikaner, Jaisalmer and Barmer area).
• Result: desert turned into fields of wheat, cotton and groundnut.

• Side effects: waterlogging (water stays in the soil because it cannot drain) and soil salinity (salt rises to the surface as water evaporates).

• Desertification means good land turning into desert. It is caused by:

• overgrazing and cutting of bushes, which leave the soil bare;

• wind blowing that bare sand onto farmland.

• Response:

• Dune stabilisation: planting grasses and shrubs on dunes to stop them moving;
• shelterbelts: rows of trees that slow the wind.

9. The Rann of Kachchh

• Location: Kachchh district, Gujarat, along the border with Sindh (Pakistan). It lies just north of the Tropic of Cancer.
• What it is: a vast seasonal salt marsh (low, flat land that floods with salty water in one season and dries out in another).
• Two parts:

	Great Rann	Little Rann
Position	North of Kachchh, along the Pakistan border	South-east of the Great Rann, towards mainland Gujarat
Size	Larger	Smaller
Key features	Flamingo breeding grounds; Khadir island (Dholavira); Banni grassland on its southern edge	Indian Wild Ass Sanctuary: last home of the Indian wild ass (khur, Equus hemionus khur)

• Seasonal cycle: 1. Monsoon (June–September): sea water from the Arabian Sea and river water (including the Luni) flood the low flat land, making a shallow sheet of water. 2. Dry season (October–May): the water evaporates and leaves a white salt flat (a hard crust of salt on dry mud). 3. Raised patches, locally called bets, stay above water as islands.

• Wildlife: it is a major breeding ground for flamingos (the Great Rann's "Flamingo City").

• Earthquake risk: very high. Kachchh lies in Seismic Zone V, India's highest-risk zone. The Bhuj earthquake of 26 January 2001 devastated the district.
• Salt making: the Little Rann is a major source of India's inland salt. It is made by the Agariya salt workers.
• Sir Creek dispute: a tidal creek in the marshes between Gujarat and Sindh. India and Pakistan disagree over where the boundary runs (see india-neighbours).

10. Dholavira on Khadir island

• Dholavira is the southern centre of the Harappan Civilisation. It lies on the arid island of Khadir in the Great Rann of Kachchh, Gujarat [2].
• Occupied: about 3000–1500 BCE. The site has a fortified city and a cemetery [2].
• Water harvesting: the city was placed between two seasonal streams so that it could collect scarce water [2].
• City plan: Castle, Bailey, Ceremonial Ground, a walled Middle Town and a Lower Town. A wall with bastions (towers that jut out from a wall) surrounds the whole city [2].
• UNESCO status: inscribed in 2021 at the 44th session of the World Heritage Committee [2].
• It was India's 40th World Heritage Site and the first Indus Valley Civilisation site in India on the list.

11. Banni grassland

• Location: on the southern edge of the Great Rann, Kachchh district, Gujarat.
• What it is: one of Asia's largest tropical grasslands. It is flat, low land with salt-tolerant grasses.
• People and animals:
• Maldhari herders are pastoral communities who raise cattle and buffalo here.

• The Banni buffalo is a hardy breed that can walk long distances at night to graze.

• Threat: Prosopis juliflora (locally gando baval) is an invasive species (a plant brought from outside that spreads fast and pushes out local plants).

• It was planted to stop the Rann's salt from spreading.
• It spread too fast, crowded out the grasses and reduced fodder for livestock.

Prelims Hooks

• Marusthali = the Great Indian (Thar) Desert. It lies north-west of the Aravallis, gets under 150 mm of rain a year, and sits on Peninsular bedrock.
• Barchan = crescent-shaped dune with horns pointing downwind. Longitudinal dune = a long ridge parallel to the wind.
• Akal Wood Fossil Park is in Jaisalmer, Rajasthan. Its fossil trunks are about 180 million years old (Jurassic) and show the area was under the sea in the Mesozoic. The marine deposits at Brahmsar add to this proof.
• Mushroom rock forms by wind abrasion (sand-laden wind cutting the base of a rock). It is not formed by water.
• Luni: rises near Pushkar (Aravallis) and ends in the Rann of Kachchh, not the sea. Its lower course is saline.
• Sambhar Lake (Rajasthan) is an inland salt lake and a Ramsar site since 1990 (24,000 ha) [3].
• Little Rann = Indian wild ass (khur). Great Rann = flamingo breeding + Khadir island (Dholavira). These two are often swapped in exam traps.
• Dholavira is in Kachchh, Gujarat. It became a UNESCO site in 2021 as India's 40th [2]. Don't confuse it with Lothal (Ahmedabad district, not on the list).
• Banni is a grassland in Gujarat (Maldhari herders, Banni buffalo, threatened by Prosopis juliflora). It is not part of Rajasthan.
• Order from north to south: Thar (Rajasthan) → Great Rann → Banni / Kachchh mainland → Little Rann lies to the south-east.

Mains Points

• The landscape keeps changing (GS-I): the area went from Mesozoic sea (Akal, Brahmsar) to Jurassic coastal forest to today's wind-shaped desert. This shows how changes in climate and sea level remake landforms. Wind and physical weathering now shape the surface, leaving dunes, mushroom rocks and playas.
• Adapting to dryness (GS-I society and geography): people store rainwater in taanka or kund, clean pots with sand and depend on oases and herding (Maldharis). Dholavira's city between two seasonal streams [2] shows that collecting scarce water is a 5,000-year-old skill in this region.
• Environmental problems (GS-III):
• desertification from overgrazing and shifting dunes;
• waterlogging and salinity in the Indira Gandhi Canal area;
• Prosopis juliflora taking over Banni;
• pressure on salt-lake wetlands like Sambhar [3].

• Responses: dune stabilisation, shelterbelts, removing invasive plants and restoring grassland.

• Disaster and security (GS-III): Kachchh is in Seismic Zone V (Bhuj earthquake, 2001), so earthquake-resistant building is a must. The Rann's marshes hold the Sir Creek boundary dispute, which affects border management and fishing rights.