Sunday, September 20, 2020

Readings: Measuring Sea Levels, Human Evolution, Elements

 Some interesting articles from the past few weeks:

1) What is global mean sea level? What is relative sea level? Is sea level rising or falling along the India coastline? Science writer Shreya Dasgupta explains how scientists measure sea level change with special reference to the Indian coast.

The Surprisingly Difficult Task of Measuring Sea-Level Rise Around India

2) A long thought human ancestor that turns out to be a contemporary.. a cousin perhaps. Multiple human species coexisted across African landscapes in the Mid Pleistocene, around 300,000 to 200,000 years ago, just when skeletal features that we recognize as 'modern' were evolving.  New fossil finds supplemented by genetics is enriching our understanding of human origins. Fine summary article by Katarina Zimmer.

Genetics Steps In to Help Tell the Story of Human Origins

3) What is an element? From Lavoisier to Mendelev to recent times, Philip Ball traces the contentious issue of pinning down what exactly an element is? 

What is an element?

Friday, September 11, 2020

Bihar: Where Many Rivers Meet

I came across this passage in Vipul Singh's interesting book, Speaking Rivers: Environmental History of A Mid-Ganga Flood Country, 1540-1885. 

 "In consequence of the frequent changes which take place in the channels of the principal rivers that intersect the territories immediately to the presidency of Fort William and the shifting of the sands which lie in the beds of those rivers chars or small islands are often thrown up by alluvion in the midst of the stream, or near one of the banks and large portions of land are carried away by an encroachment of the river on one side, whilst accession of land are at the same time, or in subsequent years gained by dereliction of the water on the opposite side;... the lands gained from the rivers or sea by the means above mentioned are a frequent source of contention and affray,and although the law and customs in the country have established rules applicable to such cases these rules not being generally known, The Courts of Justice have sometimes found it difficult to determine the rights of litigant parties claiming chars or other land gained in the manner above described"

It is a section of the preamble of The Bengal Alluvion and Diluvion Regulation of 1825 which the East India Company passed to assure a regular income from Diara lands. 

Diara land are ephemeral parcels of land that accrete to river banks or emerge in the middle of the river channel by sediment deposition. They can disappear in a decade or so as a major flood cuts away the river bank or erodes an island, only for newer land to appear elsewhere along this meandering fluid riverine landscape.

The satellite imagery covering the region between Patna in the west to Munger in the east forms the heart of this mid -Ganga floodplain.

Diara lands were traditionally farmed by landless peasants for the few months of the year that they were above water and then abandoned during monsoon inundation. There was no concept of ownership of these lands. The East India Company in its quest to maximize land revenue decided to regulate ownership of the Diara. It didn't always work in practice. Zamindars were reluctant to report the ground situation accurately and maps became outdated as topography and landscapes shifted quickly. Diara lands remained and still are a source of dispute.

Fascinating is the struggle outlined in the book of two long lasting empires with this river system. Before the Mughals, the Afghan ruler Sher Shah Suri occupied this region and had adapted to the capricious environment to his advantage. The Mughals though faced a different problem. Their power center was far to the west in Delhi and Agra. Carrying grains and goods from Bihar to Agra-Delhi using pack animals wasn't possible, since the expenses of feeding these animals would have left very little surplus. Being children of the Eurasian steppe, they preferred the horse and land transport, and that meant that they were unable or unwilling to develop a river navigation network on a commercial scale. The direction of river flow also worked against them. Sailing goods-laden boats upstream was challenging, especially as Vipul Singh points out, the Ganga upstream of Varanasi becomes difficult to negotiate. As a result the Mughals could never exploit or control this region fully. 

The British though found the river to their liking. The Grant of Dewani of Bengal, which the East India Company won in 1765, extended to the mid Ganga floodplains. The Company's main port lay downstream in Calcutta and their major markets across the seas in China and Europe. Using their expertise in navigation they soon set up a thriving trade in saltpetre, calico, opium and silk. Slowly, they also began imposing a linear topography on these curving meandering rivers. The building of embankments, canals, and barrages was thought necessary to control the inundation that could lead to a loss of a cropping season. The various Regulations and Acts meant to ensure a permanent and uninterrupted stream of revenue ended up changing the people's interaction with the river. 

These land regulations, beginning with the Permanent Settlement of 1793, entrenched the power of hereditary Zamindars who became Company rent collecting agents. It became especially hard for the landless to eke out a living as they saw even the ephemeral parcels of Diara which they had been farming now being allocated to the nearest Zamindar and his tenants. Large scale flood control projects carried out by Zamindars and encouraged by Company revenue officers began reshaping the ecology of the floodplains with embankments preventing floods in one region but exacerbating them on the opposite side or in downstream areas. Embankments also prevented smaller local streams from draining into the larger rivers, resulting in the water-logging of fields. Praveen Singh in The colonial state, zamindars and the politics of flood control in north Bihar (1850-1945), details how a web of social and economic interests spurred on this construction spree despite warnings from irrigation engineers about the detrimental effects of embankments.

Vipul Singh also emphasizes the linkage between physical processes and cultural evolution.  A unique Bihari regional identity emerged based on the homogeneous ecology, similar agrarian practices and a shared reverence for the Ganga. 

The Ganga of the plains is a turbid river. It transports several hundred million tons of sediment to the Delta. In this section of Bihar, it is joined by the Sone from the south and the Ghaghara, the Gandak and the Kosi from the north. The Kosi and the Gandak are especially sediment rich, carrying a suspended sediment load of 80 million tons per year and 43 million tons per year respectively. All this sediment is what makes this region special. A significant fraction of it gets deposited every year in the river channel and its floodplains. Over time, the Ganga and its tributaries have built vast alluvial deposits, through which the river finds its way, often getting choked on its own sediment, and then breaking free by cutting a new path for itself. This abundance of water and sediment has formed a complex fluvial ecosystem of meandering channels, river islands, abandoned courses, oxbox lakes, ponds, and wetlands. The organic rich silt deposited across floodplains by the rivers during monsoon inundation nourishes multiple crops. Life's daily rhythms became embedded in this ecology and its inhabitants evolved farming practices adapted to the changing tune of the environment.

There was linguistic pride too, not in one common 'Bihari' language, but in the various dialects spoken 'eh /e paar' and 'oh o paar'; this side of the Ganga and on the other side. Bhojpuri was the dialect of the Champaner area north of the Ganga, while to its east on the north side was spoken Maithili. In the Patna region on the south side was Magahi and towards the east near about Munger was Angika. These vernaculars with their common folk tales, poetry, and myths about deities, changing seasons, local plants and animals, and the Ganga, knitted the region together, away from the pull of the Delhi-Agra-Awadhi influence which lay to the west and the Bengali cultural sphere towards the east.

Magh ke garmi, Jeth ke jar
Pahila pani bhar gail tar,
Ghag kahen ham hoban jogi,
Kuan ka pani dhoihen dhobi

[Heat in Magh (January-February), cold in Jeth (May-June),and the tanks filled with the first fall of rain, are the signs of drought. Ghagh says that I will become a beggar, and the washer-men will wash with well-water.]  

This is a gem of a book. Highly recommended reading! 

Sunday, September 6, 2020

Hutton On Erratics

 "There would then have been immense valleys of ice sliding down in all directions towards the lower country, and carrying large blocks of granite to a great distance, where they would be variously deposited, and many of them remain an object of admiration to after ages, conjecturing from whence, or how they came. Such are the great blocks of granite which now repose upon the hills of Saleve".

... James Hutton : Theory of the Earth (1795). 

This passage is quoted in Jamie Woodward's book The Ice Age: A Very Short Introduction, and it is one of the earliest attempts to explain 'erratic boulders'. These are boulders sitting on a surface made up of a different rock type than the boulder, indicating that the boulders have been transported from a far away terrain. The great blocks of granite observed by Hutton were scattered on a limestone landscape that was part of the Jura mountains on the border between France and Switzerland.  Just how these boulders got to their present location was the subject of a lively debate in the late 1700's and the 1800's. Hutton suggested they were brought there by glaciers. Other naturalists, taking inspiring from Scripture, proposed that they were transported by Noah's flood. 

Erratics implied that glaciers must have been much larger in the past. Hutton never developed his thinking about glaciers into a full explanation. That would take several more decades of debate. Erratics found in Alpine regions and on the European and North American temperate plains became part of a growing body of evidence for past climate change.

Closer to home, the picture below shows an 'erratic' made up of a high grade metamorphic rock and sourced from the mountains seen in the background. The location is Darma Valley, Kumaon Himalaya.