Monday, March 7, 2016

History of Indian Geology

Geologists, a study found, are the happiest students in campus. Being the only species that can survive just on fermented products, it is not a surprise. There are two thing geologists are fascinated about - rocks and on-the-rocks. Indian geologists, however, have not received the fame their western counterparts enjoy. You don't see Bollywood movies where geologists save people from deadly volcanoes or earthquakes. Indians have been exploiting the vast mineral resources of India for thousands of years. Books have been written describing the locations and identification criteria of precious stones and metals. But, geology as a subject, was brought to India by the Englishmen who wanted to find all hidden resources in the new land that they now governed. East India Company started mineral exploration in India from 1774.

The early geological observations was made in India not by a geologist, but by a zoologist named Francis Buchanan. He surveyed Mysore in 1800 and Bengal between 1807 and 1814. It was Francis who started the Alipore zoo in Kolkata. He noted down in details all the rocks he saw, even those which were used to make temples. He penned his observations in his book ‘Journey from Madras through the countries of Mysore, Canara, Malabar’. Again, it was a statistician named W.H. Sykes who recognised and coined the term ‘Deccan Trap’ in 1833. ‘Deccan’ comes from ‘Dakshin’ meaning south, and ‘trap’ from the Swedish word ‘trappa’ meaning stairs or terraces. These continental flood basalts formed at the end of Cretaceous Period triggered by the India-Seychelles break-up. Some blame the dangerous Deccan volcanism for the extinction of the dinosaurs. Bones of dinosaur was recovered from beneath the traps in Jabalpur by Sleeman. The bones of the Titanosaurus indicas was sent to Kolkata. The bones were confirmed to be that of dinosaur only in 1877. Decades later the dinosaur was gone. The Titanosaurus was rediscovered in 2013. It shy dinosaur was hiding inside a cupboard in Kolkata's Geological Survey of India.

The Doom of Dianosaurs

While the first geological map in the world was made way back in 1743, India had Her first geological map only in 1821. The map was that of Hyderabad, made by Dr. H W Voysey, often called as the father of Indian geology. In fact, geology as a science was taken up for the first time by Asiatic Society of Calcutta in 1808. The 27 year old geologist, H W Voysey, was sent to Calcutta as Surgeon of Trigonometric Survey. Trigonometric survey of entire India was started by William Lambton in 1806. George Everest assisted Lambton, and later succeed him. Appointment of a geologist in Trigonometric survey puzzled Voysey’s colleagues. Hastings had to clarify the need of a geologist in India. A geologist was necessary to understand the density of the  different rocks in the subsurface that deflected the plumb line while taking trigonometric measurements. Apart from gravity, there were magnetic anomalies that affected the surveys as well. One eccentric Dr. Robert Tytler died while trying to hunt down the magnetic pole near one such anomalous ferruginous hill in Gwalior. Voysey came to India to simply help in understanding the anomalies, in which he was not very successful. His mapping did help in understanding the geology of India. However, understanding geology was not why the government paid him. Despite objections from George Everest, Voysey’s salary was cut due to long absence from regimental duties, and he resigned from the post. Soon after, he died of malaria at a young age of 33 years while travelling to Kolkata (Calcutta).

The year before Voysey’s death, in 1823, local Indians presented Captain S Webb with ‘bijli ki har’ - the bones of lightening. These Himalayan fossils were used by local as charms, or by native doctors as medicines. Webb knew that the British would be able to make a better scientific interpretation of these fossils. He send them to The Royal College of Surgeons of England. The fossils were interpreted as an evidence of the great flood. More surveys were undertaken to find the animals that perished in the flood. Attempt was also made to relate the fossil finds to ancient Indian texts. When a giant fossil of turtle was discovered, some wondered if it was the Kumra (tortoise) Avatar of Vishnu. More vertebrate fossils were discovered from what is now known as the Siwalik Group. The name is taken from the Siwalik Hills. Siwalik literally translates to the ‘tresses of Lord Shiva’. Siwalik group are molasses deposits formed by erosion of sediments from the rising Himalayas. They are around 5000m thick and cover the entire Indo-gangetic plain. The dead animals of Siwalik provided the fundamentals in understanding the Mio-Pliestocene epoch. They unfortunately said nothing about the great flood, nor was the fossil of Matsa (Fish) Avatar ever recovered!

The real need of geologists in India came from the coal industry that fuelled the Industrial Revolution in Britain. Raniganj Coalfield was the first field to be commercially mined in India. It was discovered in 1774 by John Sumner and Suetonius Heatly of the British East India Company. A new coalfield was discovered in Angul, Odisha in 1837. It was the Talchir coalfield, and it would bring a new puzzle for the geologists, to which we will come back later. Mining was mostly haphazard until the Coal Committee of India was formed in 1836. Geologist D. H. Williams was called from Britain to do a survey of Ranijanj, Jharia and Karanpura coal fields. He was appointed the Geological surveyor in 1846. Unfortunately, he fell from his elephant and died of ‘jungle fever’ in 1848. Three years later Geological Survey of India (GSI) was officially formed.

Establishment of GSI attracted more European geologist to India. The Irish Medlicott brothers made immense contribution towards Indian geology. They worked mostly around central India. While elder brother Joseph found the important Narmada-Son lineament, younger brother Henry worked the Vindhyas in detail. Proterozoic Vindhyan formation contains one of the oldest known life form on earth. Henry laid the foundation of Himalayan geology and is also credited for coining the term ‘Gondwana’ in 1872. ‘Gondwana’ means the ‘land of Gonds’. ‘Gond’ was probably first used by the Afghan traders for the Khond (hill) tribes in the 11th century. The rock Khondalite (Garnet-Sillimanite-Schist) also takes its name from the same tribe. It was the coals of Permian formations of Gondwana that attracted the geologists. Glossopteris was the key fossils of the Gondwana coals. Joseph identified the Lameta Formation and sub-divided the coals into Talcher, Damuda and Mahadevas in 1860. Joseph also noted the difference of these rocks from those of Vindhyans. The latter was only found north of the Narmada-Son lineament. However, it was not the Medlicott brothers, but Blanford brothers who found the big puzzle.
While studying the coal beds in mid 1950’s the Blanford brothers found huge boulders that could not have been carried by anything other than glaciers. On noticing closely, these boulders had stripes that confirmed them as glacial deposits, something unexpected in these part of the world. Similar boulders were soon found all across India. Mr Oldham correlated them with similar beds seen in Australia. One way of explaining the puzzle was ice-age, a time when glaciers covered most of the earth. As earth warmed up, the ice melted leaving behind the glacial deposits. Forests took over that formed the Permian coal beds.

Before the glacial puzzle was solved another came up further north, on the foothills of Himalayas. It was the old puzzle of gravity anomaly that Voysey was not able to solve. Some errors in positioning were noted by the surveyors while doing trigonometric survey south of the Himalayas. The position from Trigonometric survey done by astronomical measurement did not match the one done by triangulation. The extra gravitational pull from the Himalayas were thought to be the reason for the anomaly by Mr. Everest. To get a better hold of the measurement a mathematician, the Archdeacon of Calcutta, was recruited.

John Pratt was a brilliant mathematician. He became the chaplain of the East India Company in 1838. In 1850 Pratt became the Archdeacon of Calcutta. While studying the anomalies he found that the results were counter-intutive. The mountains attracted the plumb line less than it should, as if they were hollow. While similar measurements near the beach had opposite affect, as if there was an invisible mountain in the ocean. Pratt wrote a paper with his observations, which went to another mathematician, George Biddell Airy, for review. Airy was already a respected scientist. Airy, the man who calculated the mean density of earth, had better explanation for the anomaly. Mountains, he explained, were blocks of lighter crust that floated on the heavier asthenosphere. Mountains have roots of lower density material and thus pulled less. The oceans have anti-roots that pulled the plumb line towards itself. Airy published his hypothesis of isotacy along with Pratt in 1855. Two years later the revolt of 1857 took place and the Queen of England replaced the East India Company. GSI, however, continued to function. Indians started to join GSI, Ram Singh being the first one to join in 1873.

If the lighter continental crust is floating, does it swim as well? That questioned would not be answered soon. The geologists would take one step closer to the answer, but not before really messing it up. Glossopteris was the main plant fossil in the Gondwana coals. The term ‘Glossopteris’ was coined by a French geologist named Adolphe Theodore decades back in 1828. It means ‘tongue fern’ in Greek. Though it looks like a fern, it was later classified as gymnosperm. They are tall trees, sometimes growing 30m high, and produce seeds. Glossopteris became extinct at the end Triassic. The fossils of Glossopteris was studied in detail by Austrian geologist Eduard Suess. He found similar fossils from not just India but also South Africa, Madagascar, Australia, South America and later from Antarctica. Glossopteris fossils of Antarctica was discovered by the famous Robert Falcon Scott. Scott could never make it out of the continent with his Glossopteris. He was buried with his fossil collection, which was recovered later.


Suess claimed in 1885 that land bridges connected the continents containing Glossopteris fossils. He named this super-continent Gondwanaland, “after the ancient Gondwana flora which is common to all it’s part.” Further studies unearthed other similar flora and fauna from these distant continents that were not connected. The mystery of this strange connection between far-away lands bred new myths, and sometimes fuelled old ones. People started to hypothesis lost continents that sank beneath the ocean.
Lemuria - The Lost Continent


Finding of the fossils of Lemurs in India and Madagascar, but not Africa, was an anomaly that confused zoologist and biogeographer Philip Sclater. He proposed in 1864 that there was a lost continent, that he named Lemuria, which acted as land bridge between India and Madagascar. Lemuria caught the fancy of occultist Helena Petrovna Blavatsky. To her it was the land where superior, and spiritually more pure, humans lived. Blavatsky moved to India in 1880 where her cult movement got help from Dayananda Saraswati's Arya Samaj, a Hindu reform movement. She wrote about it in her book ‘The Secret Doctrine’. After she died of influenza she was succeeded by her disciple Annie Besant. The Tamil politicians later misused the discredited idea of Lemuria. Lemuria became the lost Tamil continent Kumari Kandam - the cradle of civilisation. According to them the last bit of the continent still exists in Kanyakumari. At that place now stands the Vivekananda Rock Memorial - where Swami Vivekananda received enlightenment before leaving for the World Congress of Religions of 1893 in Chicago. That piece of rock, where the memorial now stands, is composed of Charnockite.

The Charnockites formed deep within the crust 550 Million years ago when India fused with Antarctica. Kanyakumari was the triple junction along which the Gondwana break-up took place in Jurassic.  We now know that there were no lost continents, but India, Africa, Antarctica, Australia and Latin America were once fused together into one super-continent that we now call Gondwana (without the ‘land’ as ‘wana’ already means land). 

Gondwana


The Charnokies were named by Thomas Henry Holland in 1893 after Job Charnock, the founder of Calcutta. It was the same rock with which the tombstone of Job Charnock was made. Holland later became the director of GSI in 1904. He realised that the geological history of India did not match that of Europe. He proposed four new geological eras for India based on the unconformities found in India. They were Archaean, Purana (Proterozoic), Dravidian ( Cambrian to Middle Carboniferous) and Aryan (Upper Carboniferous to recent).


GSI continued to function actively after Independence. It was headed mostly by European geologists. However, Indians were being trained in the subject in colleges like Presidency College Kolkata where geology was taught since 1892. Maharajapuram Seetharaman Krishnan was the first Indian director of GSI. His book on Indian stratigraphy is still read geology students of India.




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