Bengal Delta, Africa Rifting, India Sand Mining

A few readings for your perusal- 

1) The future of Bengal Delta. With this succinct title Dipen Bhattacharya has written an informative article on the origin and evolution of the Bengal Delta. The Bay of Bengal was created when India broke away from eastern Antarctica about 130 -120 million years ago in the early mid Cretaceous. The basin expanded as India drifted northwards. From Cretaceous to Oligocene times (120-25 million years ago) rivers from Peninsular India were providing most of the sediment being deposited in the Bay. Himalaya derived sediment started overwhelming Peninsular river input from about 25 million years ago. K.S. Krishna and coworkers have very elegantly demonstrated this in their study of sediment pathways in to the Bay of Bengal.

Dr. Bhattacharya has traced the evolution of the delta into more recent times, explaining the role of the Pleistocene ice ages in delta growth. The delta’s future too is at risk with dam building and ground water extraction amplifying the changes due to global warming induced sea level rise. Well worth reading.

2) Eastern Africa Is Splitting Apart, but Not Where We Expected.  Africa is tearing apart along a north south oriented corridor from the Red Sea to Mozambique. Plate motion has formed the famous rift valleys of Ethiopia, Kenya, and Tanzania, as the crust stretches and subsides along faults. Kimberley Cartier explains the geological set up of the region and the stages in which continents break apart with oceanic basins eventually forming along the initial zones of continental rifts.

Why this region of Africa is rifting is not all that easy to explain. If you look at the plate tectonic map of Eastern Africa and the adjacent Indian Ocean and Arabian Sea you will notice that the oceanic Somalia and Indian Ocean tectonic plates are pushing into East Africa. For continents to split and be pulled apart, there have to be extensional forces generated. These are usually provided at the locus of rifting by the mantle doming up, thereby breaking and pushing the lithosphere away, and by one end of the plate subducting underneath another overriding plate. The subducting oceanic crust becomes denser and heavier as it sinks deeper, pulling the rest of the plate with it.

After the breakup of Gondwanaland, the northerly movement of the India plate through the Cretaceous was sustained by the pull force of the northern edge of the India plate sinking under Asia. On the other hand, Eastern Africa is surrounded by plate spreading zones. There is no pull force available for eastern Africa, only the localized extensional stresses due to mantle upwelling.  Is that providing adequate horizontal traction at the base of the Africa Plate for the crust to break apart and stretch? For a deeper understanding into the mantle forces responsible for this, I will recommend J Micheal Kendall and Carolina Lithgow-Bertelloni ‘s article- Why is Africa Rifting?

3)  India’s rivers bear lasting scars from relentless sand mining. Some years ago I heard a podcast on Planet Money about a Jamaican beach that was stolen. An estimated 500 truckloads of sand was hauled away in the middle of the night. Sand is big business all over the world. Indian river beds too are being plundered for their sand to satisfy the demands of the booming construction industry. Sahana Ghosh explores how scientists are surveying Indian rivers using field observations and satellite data. They are trying to track down the amount of sand being extracted and the environmental impact of sand mining.

Deep Sea Mining, Early Indus Farmers, Indus Basin Dams

Some readings over the past couple of weeks- 

1) The Promise and Risks of Deep-Sea Mining: In late 1988 I visited the National Institute of Oceanography in Goa for a job interview. The buzz in the marine geology labs was about the discovery of manganese nodules on the deep sea bed of the Indian continental shelf. At that time, exploration had just started and the technology was not advanced enough to mine these lumps which contained, besides manganese, other metals like cobalt, nickel, and copper.  The nodule deposits were being looked at as a future resource. 

That day is upon us. Many countries have expressed an interest in mining the deep-sea bed for metals required for the transition away from fossil fuels. Metals concentration of Mn, Co, Ni, and Cu also occurs around hydrothermal vents. Not much is known about the ecology and biodiversity of these remote sites. Most experts feel that mining will result in extensive damage to the sea floor ecosystems and to life in the surrounding water column.

Daisy Chung, Ernest Scheyder, and Clare Trainor describe what is at stake in this beautifully illustrated article published by Reuters. 

2) Indus Valley farming started later than thought, radiocarbon study shows:  Mehrgarh, in Balochistan, Pakistan, was thought to be South Asia's oldest farming settlement going back to around 8000 B.C. New carbon dating of grains using a more robust dating method called Accelerator Mass Spectrometry has revised the date of earliest occupation to around 5200 B.C. Subhra Priyadarshini writes about the implications of this new date with regards to the origins and spread of farming in South Asia and cultural linkages of Mehrgarh to the Indus Civilization. 

3) Water Towers of the Indus Basin: Last month's heinous terrorist attack in Pahalgam, Jammu and Kashmir, India, has refocused attention on the Indus Water Treaty between India and Pakistan and the many hydropower projects that India is planning on the Indus and the Chenab rivers. These rivers provide water security to vast areas of India and Pakistan. 

Despite the importance of these rivers to local livelihoods, hydropower projects are being built without due  consideration being given to the impact dam construction and climate change will have on the Himalaya ecosystem..  

Parineeta Dandekar (story), Abhay Kanvinde (photos), and Michelle Hooper (story map) meticulously document the completed and planned hydropower projects along the Chenab river and point to the lapses in science and environmental governance that have taken place during the project planning process.

Deep Sea Mining, Indian Ocean, Infectious Diseases

Some readings for you:

1) Mining the bottom of the sea: The deep sea bed is considered the last frontier on earth for mining. Large patches of the sea bed are littered with metallic lumps or nodules rich in manganese, cobalt, zinc, and nickel. These elements are considered vital for powering the world's green economy. Nauru, a tiny Pacific Ocean island nation situated northeast of Papau New Guinea, along with a Canadian mining company, wants to start mining a region of the Pacific between Hawaii and Mexico known as the Clarion-Clipperton Zone. Scientists warn that a hurried push to mine the deep ocean bed will result in an irreversible loss to biodiversity, ecologic functioning, and ocean health. Elizabeth Kolbert writes about the complex legal and regulatory issues and conflicts of interest related to international deep sea mining.

As things stand in June 2024, a deep sea mining code is still being decided by the International Sea Bed Authority. Rohini Krishnamurthy of Down to Earth has the latest news on the progress made on this issue. Negotiations are hampered by a lack of basic science and divergence of views between member states.

2) Indian Ocean headed for a near-permanent state of marine heat wave:  Rapid fossil fuel emissions over the past century or so has changed the earth's energy balance. More energy is now coming in than is being radiated out to space. More than 90% of this excess energy is ending up in the ocean as heat. As a result, the world's oceans are warming up. The Indian Ocean is warming rapidly too. Recent studies have found that it may be heading towards a scary sounding situation known as 'permanent heatwave state' where the sea surface temperatures exceed a threshold value for 220-250 days a year.

Environment and climate journalist Nidhi Jamwal summarizes the findings of this research and a new book titled The Indian Ocean and its Role in the Global Climate System. The consequences are far reaching, impacting tropical cyclones, biodiversity, and fisher folk livelihood.

3) Probing the pathogens that afflicted ancient humanity: Pathogens and humans have been co-evolving for millennia. Paleoanthropologist John Hawks charts out the history of some of the common infectious diseases afflicting humanity. Infection patterns are not random. Rather, they follow networks of transmission shaped by ecology and culture. Very illuminating essay!

Readings: Gagging Indian Scientists, Human Evolution, Sand Mining

From the past couple of weeks:

1) Slow Subsidence of Scientific Institutions: As land movement and destruction of homes in Joshimath Uttarakhand became a prominent talking point, the Indian government reacted like it usually does when faced with an awkward situation concerning its own accountability. It imposed a gag order on its scientists, forbidding them from talking to the media until publication of a final report. Dinesh C. Sharma offers a thoughtful perspective on the corrosion of autonomy of India's scientific institutions and the damage this withholding of information does to open and informed debate. 

2) Teeth Reveal How Brains Developed In Utero: How fast did our ancestors brain grow before birth? When did patterns of brain growth become more human like? Teeth start developing very early in a fetus at about 20 weeks old and they fossilize well too. Researchers found a relationship between molar length and prenatal brain growth by studying teeth from skeletons of various primate species and comparing them with gestation length and mass at birth of each species. The final conclusion was that rates of pre natal brain development increased during hominid evolution and became more human like about one million years ago.  By anthropologist Tesla Monson.

3) Grains of Sand: Too Much and Never Enough. This is a topic of great concern in India too. Unregulated sand mining is stripping river valleys barren of sand, in turn changing river morphology and devastating habitats. Alka Tripathy-Lang writes about the global demand for sand and its impact on environment and livelihoods. What is the future for this resource? Will we learn to use it sustainably?  I'll also recommend this Planet Money podcast episode on Peak Sand featuring a stolen beach! - Episode 853: Peak Sand. 

Kolar Gold Field

Geology and Livelihoods #19

I came across this excellent documentary on the Kolar Gold Field via Twitter. The film is directed by Basav Biradar and produced by Sahapedia.

Email subscribers who are unable to see the embedded video can watch it here- In Search of Gold.

Like many established mining towns, Kolar too saw generations of the same family work in the mines. Son followed father into the dark shafts. Mining provided employment, but it was dangerous back breaking work. The documentary highlights the lives of workers and their struggle for better work conditions. 

Kolar gold is late Archaean in age with mineralization taking place between 2700-2500 million years ago. There are two types of deposits. There is a "stratiform sulphide type", so called because the gold bodies are contained within iron sulphide rich volcanic and sedimentary layers. These deposits formed on the sea floor contemporaneous with volcanism and sedimentation. The second type is a hydrothermal deposit wherein mineralizing fluids mobilized and precipitated gold in veins along N-NE oriented fracture zones. This mineralization event occurred at a later stage when magmatism and metamorphism affected the host terrain.

But do watch this for the many personal stories of the people who worked the mines. 

Links: Indian Monsoon, Hominin Footprints, Copper Mining

 Few links from past few weeks:

1) Rethinking the Indian Monsoons - This is a cracking good talk on the Sandip Roy Show with Dr. Sulochana Gadgil, meteorologist and an authority on the Indian monsoons. Dr. Gadgil talks about her career researching the monsoons. She elegantly explains the common misconceptions about its origins, pointing out the changes in monsoon patterns that have taken place over the past couple of decades, the difficulties in constructing accurate computer models and in predicting the future behavior of this complex phenomenon. She also draws an intriguing connection between variation in rainfall and crop yields. Drought years have lower yields, but there are no commensurate gains with excessive rain. There is also some advice on making Indian agriculture more resilient to climate change. All this interesting science is mixed with some delightful vignettes of her personal life too. Dr. Sulochana Gadgil is married to the well known ecologist Dr. Madhav Gadgil.  Exceptional interview! 

2) Multiple Bipedal Hominin Species 3.6  million years ago- A good write up of a reassessment of long forgotten set of footprints, from Laetoli, Tanzania. Scientists made new casts, developed digital reconstructions and compared them with a range of creatures. It looks like besides the famous Lucy (Australopithecus afarensis), another hominin species walking with a different gait coexisted in this area.

3) Copper Mining of the Future- Renewable energy infrastructure will require a lot of copper. Many times more than what we are mining now. Maybe, instead of blasting copper rich rock in giant open pit mines, we can suck out copper rich brines out of dormant volcanoes, like drilling for oil? Some speculation about this wild sounding idea. 

The Early History Of Coal Mining In India

India's coal reserves come from the Permian-Early Mesozoic continental rift basins situated in eastern India.

Coalgate is making headline news almost every day in India but Vikram Doctor on his blog On My Plate writes about the many shenanigans of early coal mining:

It was an American who first tried to develop systematic coal mining in India. Suetonius Grant Heatly was born in Newport, Rhode Island, but during the American Revolution his family was loyal to the British, and fled to Britain. Heatly joined the East India Company in 1766, possibly because Lord Cornwallis, the Governor-General of India, had earlier headed the losing British forces in America, and was expected to favour the British loyalists of that conflict. Heatly became Collector of Chotanagpur and Palamu (now part of Jharkhand). And it was while travelling here that he noticed local tribal people burning coal fires, Jha notes that the seams are found exposed on the surface in these areas. This was not far from the Damodar river and Grant, along with another East Indian man, John Sumner, realised that coal could be mined and floated down the river to Calcutta.

Grant and Sumner teamed up to get Company permission to mine coal. Yet their first application, in 1770, was rejected. Jha suggests this was because the Company was unsure of its rights of mineral extraction and, in any case, preferred to use its monopoly position to import minerals from Britain and sell them at high prices in India. Also, they were apprehensive about Indians learning how to use these minerals: “They even feared that once the natives acquired the art of smelting metals and the manner of casting them into cannon shot and shells that they would become masters of the latter.”

There were many early attempts in the late 1700's to early 1800's to mine coal but these ventures were never profitable due to hazardous mining conditions, legal disputes over land rights, poor transport and the better quality of imported English coal.  Then later in the 1800's demand reached a point whereby mining Indian coal became economic again. The East India Company backed English entrepreneurs who leased land from local rulers.  There were Indian businessman too. Among them who made a fortune in coal was Dwarkanath Tagore, grandfather of one of the most famous Indian poet writers Rabindranath Tagore. 

Tirthankar Roy in his book The East India Company describes the precarious balance the Company had to maintain between monopoly and allowing its agents and other merchants to conduct private trade in competition with the Company. Vikram Doctor's article brings out this aspect of  Company business life quite well along with the ruthless opportunism of these early coal entrepreneurs.

Read more here.

Gold And Metal Exploration In The Deep Sea

The recent interest in metal sulphide deposits localized around deep sea hydrothermal vents has been nicely summarized in an article in the New York Times.

Gold and copper are the main metals of interest along with silver, zinc and cobalt. The deposits are not randomly distributed on the sea floor but are near undersea volcanic activity with the Pacific areas along Papua New Guinea and Fiji being of special interest.

Years ago as a student I had visited the National Institute of Oceanography in Goa, India. At that time the thrust of research was on the origin and distribution of manganese nodules which could be found in several zones in the Indian ocean. That never became a commercial venture due to probably the low concentration of the nodules and the high costs of extraction.

These new ventures though are going to be operating on a gigantic scale:

...Last year, Nautilus won a 20-year lease to mine a rich deposit in the Bismarck Sea, in the southwestern Pacific. The mounds are a mile down. The company says the site holds about 10 tons of gold and 125,000 tons of copper.

Nautilus plans to start mining next year but also cites possible delays. It is building robots up to 25 feet tall that are to collect sulfides and pump them to the surface. Barges are then to carry the seabed minerals to Rabaul, a Papua New Guinea port some 30 miles away.

Robots 25 feet tall and maybe even taller in the future.

Hollywood won't be far behind..