Lonar Lake, also called Lonar Crater, is a salty and alkaline lake located in Lonar, 79 kilometers from Buldhana in the Buldhana district of Maharashtra, India. It is recognized as a National Geo-heritage Monument.

Lonar Lake lies inside an impact crater formed by a meteorite hitting Earth during the Pleistocene Epoch. It is one of only four known impact craters in basaltic rock on Earth. The other three are in southern Brazil. The lake has an average diameter of 1.2 kilometers (3,900 feet) and is about 137 meters (449 feet) below the crater’s edge. The crater’s rim is approximately 1.8 kilometers (5,900 feet) wide.

Earlier estimates suggested the crater was about 52,000 years old, but newer research indicates it is approximately 576,000 years old.

Lonar Crater is located on the Deccan Plateau, a large area of volcanic basalt rock formed by eruptions about 65 million years ago. At first, some scientists thought the crater might have been caused by volcanic activity. However, it is now understood to have been created by a meteorite impact. The lake’s water is both salty and alkaline.

Scientists, including geologists, ecologists, archaeologists, naturalists, and astronomers, have studied the lake’s ecosystem. Organizations such as the Smithsonian Institution, the United States Geological Survey, the Geological Survey of India, the University of Sagar, and the Physical Research Laboratory have conducted detailed research on the site. In 2007, scientists discovered that the lake helps fix nitrogen in the soil.

A 2019 study by IIT Bombay found that the minerals in the lake’s soil are similar to those in Moon rocks collected during the Apollo Program. In November 2020, the lake was declared a protected Ramsar site.

Lonar Lake is an endorheic (closed) basin, nearly circular in shape, formed by a meteorite impact about 50,000 years ago. It is one of the four known impact craters in basaltic rock on Earth. The lake has high salinity and alkalinity because it has no outlet, causing minerals to concentrate as water evaporates. Animals living there include the vulnerable Asian woolly-necked stork, common pochard, and grey wolf. It is a National Geological Monument recognized by the Geological Survey of India (GSI). It is the only crater lake in India formed by a meteorite impact. The site was identified as unique by British officer C. J. E. Alexander in 1823. Hemadpanti temples are located near the lake. Recently, the lake’s water turned pink due to the presence of salt-loving microbes called haloarchaea. These microbes produce a pink pigment and live in highly salted water.

Geographical features

A group of small hills surrounds the basin, which is shaped like an oval, almost round, with a top edge measuring about 8 km (five miles) around. The sides of the basin rise sharply at an angle of about 75°. At the bottom of the basin’s sides, the lake has a shoreline that is about 4.8 km (three miles) around. The slopes are covered with tree-savannah, which includes teak (Tectona grandis), Wrightia tinctoria, Butea monosperma, and Helicteres isora, and with shrub-savannah, which includes Acacia nilotica and Ziziphus spp. Along the lake’s edge, non-native Prosopis juliflora is growing. The main crops grown in the area include millet, maize, okra, banana, and papaya.

The lake’s water contains different types of salts and soda. During dry weather, when water evaporates and the water level drops, large amounts of soda collect. Two small streams, called Purna and Penganga, flow into the lake, and a well of fresh water is located on the southern side, near the lake’s edge.

Geological origin

Lonar Lake is located within the only known extraterrestrial impact crater found in the Deccan Traps, a large basaltic formation in India. At first, scientists thought the lake was formed by volcanic activity, but it is now understood to be the result of an impact from a comet or asteroid. Evidence such as plagioclase that has changed into maskelynite or shows planar deformation features confirms the crater was formed by an impact. Scientists believe only the extreme pressure from a very fast impact can change plagioclase into maskelynite or create planar deformation features. Other signs, including deformed basalt layers around the crater, shocked breccia inside the crater, shatter cones, and a non-volcanic layer of material surrounding the crater, all support the impact origin of Lonar Lake.

The crater has an oval shape, and the space rock that caused the impact came from the east at an angle of 35 to 40 degrees.

Scientists have estimated the crater’s age in different ways. Earlier studies using thermoluminescence suggested the crater was about 52,000 years old. More recent argon-argon dating indicates the crater is much older, approximately 570,000 ± 47,000 years old. This older age matches the level of erosion seen on the crater’s rim.

Studies have divided the geological features of the Lonar crater into five distinct zones, each showing unique landform characteristics. The five zones are:

History

The lake was first written about in old religious books called the Skanda Purana and the Padma Purana.

A document called the Ain-i-Akbari, written around the year 1600, describes the area as follows:

These mountains have everything needed to make glass and soap. There are also places where saltpetre is made, which provide money to the government through taxes. A spring on the mountains has salty water, but the water from the middle and edges is completely fresh.

The lake is located in Buldhana district, Maharashtra. This area was once part of the Maurya Empire and later the Satavahana Empire. The Chalukyas and Rashtrakutas also ruled there. During the time of the Mughals, Yadavas, Nizam, and British, trade in this region grew. Many temples near the lake are called Yadava temples or Hemadpanti temples, named after Hemadri Ramgaya.

In 2022, the government of Maharashtra started planning to make the area a tourist spot. On September 8, 2000, the government declared the lake and nearby land as Lonar Wildlife Sanctuary. On February 21, 2017, the government of India declared the surrounding area as an Eco-sensitive Zone.

Ambar Lake

There is a small round hole about 700 meters (2,300 feet) away from the main lake. Scientists think this hole may have been created by a piece of the meteor that formed the lake. Near the lake, there is a temple dedicated to Hanuman. The statue in the temple is made of rock and is believed to have strong magnetic properties. Farmers in the area use water from Ambar Lake. This lake is sometimes called Chhota (little) Lonar.

By-products of the lake

The Gazetteer records the work of British officials and scientists, including Colonel Mackenzie, Dr. I. B. Lyon, J. O. Malcolmson, and Plymen, an agricultural chemist. Some parts of Plymen’s report, shown in quotes, provide useful information.

Salt deposits found in the lake are unusual. Compared to Sambhar Lake in Rajasthan, India, which is famous for its salt, the Lonar Lake deposits are different. At Lonar, the most important salt is soda carbonate, while Sambhar Lake’s value comes from sodium chloride, or common salt. The ways these salts form are also different. It is likely that the Lonar salts come from an unknown source in the lake’s bed. Water flows into the lake continuously, and no water is lost except through evaporation. However, the main stream and smaller rainwater sources cannot explain the amount of salt found. This is because the area around the lake has plenty of plant life, especially where the main stream flows. If the water contained salt, the plants would not grow well and would eventually die.

The salts collected from Lonar Lake vary in type and composition. People who handle these salts can easily tell them apart by appearance. Five or six main types are named, but there is no clear boundary between them. Their composition depends on when and how they form. Today, large amounts of these salts are found along the lake’s shores.

During the process of forming crystals, sodium chloride (common salt) and soda carbonate combine to create different products.

Kala Namak and Nimak Dalla appear as white, crystal-like masses. Khuppal is a solid, dense lump made of roughly equal parts of carbonates and chlorides. Pipadi, which has a similar chemical makeup, looks different. It often has a slight pink color, and hollow spaces exist between its crystal-like layers. Bhuski has no clear structure and is a soft, flaky powder mixed with impurities. It resembles baking soda or small salt particles. These salts are not collected in the same way or at the same time of year. Pipadi and Bhuski form along the lake’s shore as water evaporates during hot weather. Pipadi is found in the upper layer and is purer than Bhuski. Except for Bhuski, the other salts are mostly pure and contain small amounts of earthy material. Further purification of these salts is not difficult.

The use of these salts for commercial purposes began in 1842, during the time of the Nizam’s government, and continued until 1903. Today, only a small local demand exists for these Lonar Lake products.

Gaylussite mineral

Gaylussite is a mineral that has been recently found in drill core samples from Lonar Lake. It is a carbonate mineral, specifically a hydrated sodium calcium carbonate, with the chemical formula Na₂Ca(CO₃)₂·5H₂O. Gaylussite forms as clear or cloudy, glass-like white to grey to yellow crystals shaped like prisms. It is an unstable mineral that loses water when exposed to dry air and breaks down when placed in water.

Streptomyces alkalithermotolerans is a type of bacterium that thrives in alkaline environments and can survive in high temperatures. It belongs to the genus Streptomyces and was found in the Lonar soda lake in India.

Lake ecosystem

The lake has two separate areas with different chemical properties that do not mix. The outer part has a neutral pH level of 7, and the inner part has a higher pH level of 11. Each area supports its own types of plants and animals. The lake is home to many different species of plants and animals.

The area is home to 160 bird species, 46 reptile species, and 12 mammal species. Birds that live near or visit the lake include black-winged stilts, brahminy ducks, grebes, shelducks, shovelers, teals, herons, red-wattled lapwings, rollers, blue jays, baya weavers, parakeets, hoopoes, larks, tailorbirds, magpies, robins, and swallows. Among reptiles, the monitor lizard is a common species. The lake also has thousands of peafowls, chinkara, and gazelles.

The area covering 3.83 kilometers (1.48 square miles) was officially named Lonar Wildlife Sanctuary by the government on November 20, 2015.

Microbial diversity

Lonar Lake often appears green most of the year because of large amounts of cyanobacteria, such as Arthrospira spp. Many types of bacteria and archaea live in the lake, including methanogens (organisms that produce methane), methanotrophs (organisms that use methane), phototrophs (organisms that use light), denitrifiers (organisms that remove nitrogen), sulfur oxidizers, sulfate reducers, heterotrophs, and syntrophs. Molecular studies of Lonar Lake sediments found many types of microorganisms, such as alveolates, fungi, stramenopiles, choanoflagellates, amoebozoans, cercozoans, and new groups of micro-eukaryotes. Scientists also found gene sequences from ciliated protozoans like Oxytricha longa and fungi from the Candida spp. in sediment samples with enriched methylotrophic bacteria. A new type of fungus, Curvularia lonarensis, was discovered in the lake.

Methylotrophs, including species from Methylomicrobium, Methylophaga, and Bacillus, live in Lonar Lake sediments. Methane-oxidizing methylotrophs (methanotrophs) were found in the surface scum on top of the lake water. A new type of non-methane-using methylotroph, Methylophaga lonarensis, was grown in pure culture from sediment samples. This bacterium, which thrives in high salt and alkaline conditions, produces organic solutes like ectoine, which are useful in biotechnology. Methylotrophic methanogenesis (a process where methane is produced using methylotrophs) has been found in Lonar Lake sediments. The main microorganism responsible for this process is closely related to Methanolobus oregonensis.

Endolithic bacteria, including those from Actinobacteria, Acidobacteria, Proteobacteria, Firmicutes, Cyanobacteria, and Bacteroidetes, and endolithic archaea from Thaumarchaeota and Euryarchaeota, were found in basalt rock samples from Lonar Lake’s crater walls and lake bed. The number and variety of endolithic bacteria in these samples were higher than those of endolithic archaea. Many of the detected endolithic prokaryotes are likely methanotrophs, methanogens, phototrophs, ammonia-oxidizers, nitrogen-fixers, denitrifiers, sulfate-reducers, and metal-reducers.

Non-symbiotic nitrogen-fixing microorganisms, such as Halomonas sp., Paracoccus sp., Klebsiella sp., Slackia sp., and Actinopolyspora sp., have been found in the lake. These nitrogen fixers can only grow in environments with a pH of 11. Some bacteria and actinomycetes from the lake can grow using components of inorganic medium that include materials similar to Martian soil.

In early June 2020, the lake turned red or pink within 2–3 days. Studies by the Agharkar Research Institute, National Environmental Engineering Research Institute, and Geological Survey of India suggested that lower water levels and high salinity caused the growth of Halobacterium and increased carotenoid levels, leading to the color change.

Religious setting

Many temples surround the lake, most of which are now in ruins. The only temple still standing is the Daityasudana Temple in the center of Lonar town. This temple was built to honor Vishnu for defeating the asura Lonasura. It is a good example of early Hindu architecture. Other temples inside the crater have statues of deities such as Vishnu, Shiva, Brahma, Lakshmi, Parvati, and Sarasvati. During the Mughal Empire, many statues were destroyed or damaged. Today, some statues have missing heads.

The Daityasudana Temple was created by the Chalukya dynasty, which ruled parts of India from the 6th to 12th centuries. It belongs to the Hemadpanthi style and has an irregular star shape. The carvings on the temple are similar to those found at the Khajuraho temples. The statue of the deity is made from a type of rock that looks like stone. The ceiling and exterior walls are covered with carvings. The base of the temple is about 1.5 meters (4.9 feet) tall, and the unfinished roof has a pyramid-like shape.

The Daityasudana Temple is the best example of the Hemadpanthi style. The image of Surya, the sun god, in a niche at the back of the temple suggests it may have originally honored Surya. However, it now honors Vishnu as Daityasudana. Lonasura was an asura who lived in this area with his siblings. Vishnu killed Lonasura, which is why the temple is named Daityasudana.

The temple is 32 meters (105 feet) long and 25.8 meters (84.5 feet) wide. It has three main rooms. The innermost room, called the sanctum sanctorum, holds a statue of Vishnu standing over the defeated Lonasura. The current statue was made by the Bholse rulers of Nagpur after the original was destroyed. The second room, called the antari, is used for individual worship. Statues of Vishnu killing Lonasura, Krishna killing Kamsa, Narasimha killing Hiranyakashipu, and Krishna and Rukmini are carved on the roof of this room. The outermost room, called the sabhamandapa, is used for group offerings and performances. This area and the entrance gate do not match the rest of the temple’s style, as they were added later after the temple was damaged in the 10th century.

The main entrance of the temple faces east. The main niche at the back has an image of Surya, the sun god, which suggests the temple might have originally honored him. The niche on the south has an image of Chamunda, and the niche on the north has an image of Narasimha. Each of these niches is built like a small temple with detailed pillars and decorations.

Many ridges on the temple have different carvings and images. Many of these images show deities and stories from the Hindu Puranas.

Threats to Lonar lake

Lonar Lake has human-related and environmental challenges, as described below:

The crater is protected as a geological landmark, and officials have acknowledged its importance for history and archaeology. However, steps must be taken to reduce the harmful effects of nearby communities and religious festivals on the local environment. Several community efforts, such as the "Save Lonar" movement, are currently working to protect the Lonar crater.