Lothal, meaning 'land of the dead' in local language, in Ahmedabad district, Gujarat, a bustling port in it's hey days (2350 BC) is now a paradise for the archaeologists. Remnants of the ancient port town with an acropolis and a warehouse are spread over an area of 64,752 square meters says Prabhas Pande an eminent seismologist of Geological Survey Of India (GSI).
Similarly Dwarka on the west coast of Saurashtra was another site of late Harappan culture. Underwater search carried out by the Marine Archaeological Centre of the National Institute of Oceanography in the Gomti creek found structures such as bastions, walls, pillars, anchors etc at a depth of 20 m indicating presence of a late medieval period harbor. Similarly in Bet Dwarka and Poomphuar at depths of five to eight meters, pottery, stone sculptures, terracotta beads, bronze, copper-iron objects etc indicate that while the Mahabharata was being fought this flourishing town was submerged.
Like Lothal there were many towns and ports for example, Dholavira (2500 BC) in Kutch district, whose remains are found spread in a 50 hectare area had one of the best planned layouts, architecture and water management systems. Artefacts indicate that the civilization started to decline around 2100 BC. Around 1800 BC the urban character was lost and abandoned in 1700 BC but once again populated in 1500 BC. Finally in 1400 BC the town was finally abandoned and was never populated again.
It is perplexing, isn't it? Why this bias of nature for Gujarat only? The answers to this question were sought by the Indian Society of Engineering Geologists in a recent brain storming session held at Lucknow. Pande tried to solve the riddle and his findings make an interesting reading.
To go to the root of the problem one has to travel in a time machine and go back to nearly 2000 millions years ago (Ma). That was Precambrian era of the earth's history. The ancient rocks of those days had already been fractured and there were three major sets of fractures. These became the weak planes along which rifts were formed later between 250 Ma to 65 Ma. These rifts are termed as the Kutch, Narmada and Cambay grabens by the geologists. The weak planes formed in the infancy also gave rise to several fault planes out of which some have remained active in the last chapter of the earth's history, the Holocene epoch. This is the period when the snow blanket over the globe started to melt. The snow melt raised the sea levels all over and Gujarat coast was no exception.
Prabhas Pande in his paper says that the northwestern part of Gujarat lies in a hyperactive seismo-tectonic domain comprising Zones V and IV of the Seismic Zoning Map of India. Gujarat is at a junction of continental plates where due to severe stresses energy at an average rate of 7.30 X 1020 ergs per year is being released. This calculation is based on a 182 year database says Pande. Between 1668 and 2001 a total of 100 earthquakes of significance have rocked the area.
Gujarat has been a centre of attraction from the pre-historic periods. Find of buried ancient civilizations, 13,000 to 8,000 years and another 7600 to 3000 years old from the sea bed in the Gulf of Cambay has already been described in an earlier story, 'Submerged towns of the past: was it a tsunami?' ( Boloji.com-14.01.07). During the pre-history period from 2500 to 1400 BC, the people of Indus Valley or Harappan civilization inhabited the landmass. So far 60 settlements of Indus civilization have been found in Kutch and out of these 40 belong to early and the remainder to late Harappan culture. The historical records for Gujarat are available from 250 BC onwards Having seen the hey days of Gupta Empire in the 4 th-5th century AD to the Arabic Muslims, Mughals, Marathas and the British rules Gujarat is a province that has seen a great variety in terms of human rulers and the Natural hazards as well. Some of the natural hazards have left their tell tale marks on the sediments thereby proving that there were many environmental vicissitudes which made the people desert their abodes and later reoccupy when the conducive conditions returned.
The conducive climate and availability of water made the Harappans to settle at Dholavira in Kutch region. They remained there nearly for a millennium. It is astonishing that they suddenly abandoned their abodes. Pande conjectures from the circumstantial evidences that possibly the Indus delta those days might have extended to this part of Kutch. In most likelihood the pre-historic rivers like Puran and Saraswati distributaries of the Indus River were debouching in to the sea in this region only. Evidences indicate that Dholavira experienced three distinct upheavals between 2000 and 1400 BC in the form of severe earthquakes. Perhaps the collision of the Indian Plate with the Asian Plate was the root cause of these earthquakes! These were must have been responsible for far reaching changes in the river drainage. The rivers like Saraswati began to vanish. Lack of fresh water might have caused people to move to safer areas!
What is seen as the great Rann of Kutch today was once upon a time an inlet of the sea. Thomas Oldham of GSI in his memoir of 1926 quoted Sir Alexander Burne's statement that the area between Lakhpat and Mundhan was on the bank of an old river Puran. In its eastern upstream this river was connected with Hakra, the lost river of the Indian desert. This river system carried the powerful discharge of the Sutlej and its tributaries in to the sea. This drainage was active between 6th and 16th centuries AD. Later when the ground suddenly moved up near Ambala the Indus drainage took a northwestern curve and Sutlej river became part of the present Indus system and Hakra became a dry channel to be filled up. The river Puran continued to flow with a diminished discharge for some more time.
A Capt. R.M. Grindlay accompanied a mission to Sindh in 1808 and navigated through the channel of Puran from Lakhpat to Ali Bandar. During the 1819 earthquake of Kucth an 80 km long and six metre high embankment came up in East-West direction. Since it was a natural embankment it was named as the 'Allah Bund'. Land south of this subsided due to the shaking. Thus huge areas were inundated by the sea waters within no time. The river too was lost into oblivion. Whatever human settlements were there in this area were completely ruined compelling people to flee to safety.
The two sites of the coastal settlements at Dwarka and Lothal were lost in a short span of time, probably due to severe fluctuations in the sea levels and resultant submergence, coastal erosion and drying up of the channels. Evidences show that the entire coast of western India sank by 12 metre around 1500 BC. There could be either one or all the three possibilities that led to the submergence of Dwarka, they are: I) A change in the level of the sea bed; ii) a massive earthquake and iii) sudden increase in the level of sea water, which could also have been due to a tsunami! Inundation of Dwarka is comparable to the flooding of the great Rann of Kutch during the 1819 earthquake. Similar mishap had taken place in Bulgaria when a great earthquake some 7500 years ago ruptured the Bosporus Strait and vast areas were marooned.
Lothal, though a prosperous and busy trade centre of Harappan civilization lost it's glory when the ancient port channel became dry due to sea level fluctuations. Pande and his co-workers conclude that Lothal was developed over a tidal salt marsh and it was left high and dry once the sea level dropped.
History has ample evidences to show that rise and fall of civilizations has been due to water. Earlier days the natural hazards due to excess or shortage of water played a key role in the survival or otherwise of the civilizations. The possibilities of natural hazard have not lessened with time. Infact they have become more fatal now because there are more people staying close to hazardous areas. The additional risk due to anthropogenic hazards has gained significance now, making coastal areas still more vulnerable.
We shall read about some ancient, prehistoric events that carved the destiny of many civilizations in the past in the Indus-Ganges interfluves