In 2001, during routine pollution studies in the Gulf of Khambhat (formerly Cambay), on the north-west coast of India, sonar equipment on National Institute of Ocean Technology (NIOT) survey boats detected regular, geometric shapes. Divers investigated and found large, rectangular blocks embedded 30-40m below water. The manmade blocks, possibly foundation stones of buildings, reignited curiosity about an ancient city that had flourished centuries before Egyptian and Chinese civilisations, and which was devoured by the sea.
Image credit: Alamy
The area where the sonar images were taken was around 8km x 1.6km – about the size of the city of Manhattan or 150 times larger than the early known settlement of Jericho in today's West Bank.
On the other side of the bay today stands the city of Dwarka. Its name means 'gateway', and its location made it the entry way for traders coming from west Asia to India via the Arabian Sea. The city was the first capital of the state of Gujarat and is one of the country's seven sacred cities. It is a place of pilgrimage for Hindus, Buddhists and Jains. Archaeological excavations here show it was a busy port from around 200 BCE.
Legend has it that the Dvaraka kingdom was founded by Lord Krishna 5,000 years ago as Golden Dvaraka
Image credit: Met Museum
In the 1930s, the Archaeological Survey of India began excavations around the pilgrimage site at Bet Dwarka, about 30km north of today's Dwarka. They uncovered evidence of settlers from the late Harappan or Indus civilisation era (2500-1700 BCE) and some submerged settlements. Although it was concluded that these settlements became submerged due to coastal erosion, the finds renewed interest in finding the legendary lost city of Dvaraka (also known as Dvaravati).
The possibility of finding the lost city of Dvaraka would be as significant to Hindus as the discovery of Noah's ark would be to Christians. Additionally, evidence of a civilisation which pre-dates the ancient Sumerians, Egyptians and Chinese would require academia to re-evaluate the development of urban civilisation.
In 1979, archaeologist Dr Shikaripura Ranganatha (SR) Rao was excavating a temple when he found a second foundation layer underneath. He uncovered more foundation layers, the final one 100m below the surface. There he found shells, pottery shards and iron artefacts, which he believed were from the 15th century BCE and from the lost city, transported to the site as the temples had shifted inland over the centuries.
Image credit: Applied Acoustic Engineering
From 1984 to 1988, Rao's teams of divers searched off the coast. They found large sandstone walls, jetties and stone anchors, similar to those retrieved in Cyprus and Syria. These underwater architectural finds have been dated to the 12th century CE and are evidence of a thriving medieval port city. Other artefacts have been brought to the surface, however, which are much older. Pieces of wood, shards of pottery, some hand tools, bones and a tooth were brought to the surface. Carbon dating showed they are from 1600-1500 BCE, in keeping with the inland Indus settlement. One piece of carbonised wood was carbon-dated as being 9,500 years old, far earlier than the Indus period. The wood is not identifiable as being a human-made object, say detractors. If it is a piece of natural timber, changes in water level (100m in 20,000 years) explain its presence as the area would have once been a forest.
The archaeology community is split into two camps: the 'Dvaraka discovered' and 'Dvaraka deniers'. Dr David Miano, presenter on YouTube channel 'World of Antiquity', is sceptical about the NIOT survey images. He questions why the GPS co-ordinates of the sonar scans have not been published nor replicated. He says that sonar imaging relies on many factors such as the speed of the vessel, the lateral and side ranges of the sonar systems, and may even be subject to software glitches.
Radiocarbon dating, which is used to date microfossils in sea level reconstructions, showed sea levels in the area had receded around 3,500 years ago and then risen again, which corresponds with the legendary city's reclaimed land and subsequent submersion. This strengthens the belief in the existence of Dvaraka which, according to legend, was built on land reclaimed from the sea.
Divers measure and record their findings at an underwater archaeological site
Image credit: Balkan Heritage Foundation/Dr Nayden Prahov
For the sceptics, no positive proof of an earlier civilisation has been found. They maintain that the use of dredging to recover artefacts means that they cannot be definitively tied to the area in which they were found.
They also argue that the pottery shards are too small to determine if they have been crafted using a wheel or handmade and point out that some finds may be natural geofacts or pottery pieces that the currents have carried from shipwrecks to the site. The pottery to date does not bear distinctive patterns, colours or seals, and the shards are too small to be identified with certainty.
The believers and the sceptics will continue to explore the area. Dr Rao died in 2013 without having established the existence of Dvaraka, but there are many who continue to hope and search for the lost city.
Sonar technology for studying the seabed
The survey ship used side-scan sonar to bounce images from the seabed to the ship's monitors. It also used sub-bottom sonar equipment, another reflective positioning system which can identify features and objects at greater depths than sonar. Sub-bottom sonar uses an acoustic or seismic energy source to trigger a pressure wave which travels down the water column and into the seabed. The returning sound is recorded using a pressure-sensitive hydrophone array and used to build an image of the geology below the seabed.
There are a variety of different sub-bottom profiling systems available, explains Applied Acoustics' Mike Calvert. Pinger systems, for example, use a ceramic transducer to produce and detect very high frequencies (2.0-20kHz). This produces a high-resolution image which can show small features but cannot penetrate deep into the seabed.
Chirp systems are also high-frequency and used for high-resolution, shallow penetration surveys (usually 20-50m, depending on sediment and water depth).
A Boomer system uses lower frequencies (500Hz to 5kHz) and can penetrate much further below the sea floor – up to 100m, and high-resolution data, dependent on the sediment type.
For the deepest penetration, a sparker sub-bottom profiling system uses an electrical charge to vaporise the sea water, which rapidly expands to produce a pressure wave. Large, high-powered sparkers can produce low frequency (down to 50Hz) and penetrate down to 1,000m, says Calvert.
"Although lower frequencies can identify deeper geology and features, there is a trade-off in resolution," he adds.
The legend of Dvaraka
The Indian epic poem, Mahabharata, tells the story of how the Hindu god of devotion, Krishna, defeated his uncle in a bitter war. Despite the victory, he did not believe his people could live in peace in Mathura, his birthplace, so he led them to the north-west coast of India to build a new city.
He came to Dvaraka (or Dvaravati), an area of land reclaimed from the sea, which was near the Raivataka mountain range where the gods lived. Krishna asked Vishwakarma, the architect of the gods, to build the city on 96 square kilometres of land recovered from the sea.
The city was built in one day. It had four main gates and could only be reached by ship. The buildings inside are described as tall and made of gold in the Indian legends of Bhugvat Puraan, Skanda Puraan and Vishnu Puraan. The 900 palaces are made of crystal and silver and decorated with huge emeralds, according to the 100,000-couplet poem, Mahabharata.
The poem also describes King Shalva besieging Dvaraka from the air, using a vimana, or flying machine, which launched missiles at the people below. Krishna responded and fired his ships' weapons, launching missiles which are described as roaring like thunder and as bright as the Sun's rays when released. The counterattack was successful, and the invading army was destroyed.
Queen Gandhari's 99 sons died in this battle, and she placed a curse on Krishna, his kingdom, his people and his sons. Shortly after, there was civil war in Dvaraka and Krishna's sons were killed. In the following 36 years no crops grew, and the Yadavas people left Dvaraka. As they were passing through the city gate, a giant wave rose and submerged the city completely.
The late Dr Narahari Achar, who was professor emeritus at the University of Memphis in the Department of Physics and Materials Science, studied the Mahabharata for mentions of asteroid showers, planet alignments and solar and lunar eclipses. Using a Cyber Sky Planetarium program, he dated the war in which the Queen's sons were killed to 3102 BCE, with Krishna's death and the tidal wave that submerged the city occurring in 3066 BCE. The ancient Egyptian pre-dynastic period is around 3150 to 2686 BCE.
