Wednesday, August 17, 2011

Reassembling Pangaea In The Year 1493

This is the second great talk I have heard on Fresh Air in the past few days. Author of the book 1493: Uncovering the World Columbus Created Charles Mann talks about the impact on the Americas and Europe due to the sudden exchange of humans, animals, plants, parasites between the continents following Christopher Columbus's voyage to the America's in 1492.

He frames this exchange within a larger geological context -

Mr. CHARLES MANN (Author, "1493: Uncovering the New World Columbus Created"): Well, if you think about it, you know, there's been a tendency in textbooks now to kind of downplay Columbus because they say he was a bad guy, and he mistreated Indians, and he discovered the Americas by accident and so forth.

But to ecologists, he was this super-important figure, and the reason is that 200 million years ago, as you remember learning in school, the world was a single, giant land mass they call Pangaea, and geological forces broke it up, creating the continents we know today. And over time, they developed completely different suites of plants and animals.

And what Columbus did was bring the continents back together. He recreated Pangaea, in effect, and as a result, huge numbers and plants and animals from over there came over here, and huge numbers of plants and animals from over here came over there, and there was a tremendous ecological convulsion, the greatest event in the history of life since the death of the dinosaurs.

As an aside.. he is right off course that after the supercontinent Pangaea broke up more than 200 million years ago, different continents had evolved different suites of plants and animals. But Europe, Asia and the America's were not completely isolated from each other from the breakup of Pangaea until the Columbian exchange. From time to time during the early Cenozoic there were faunal exchanges ..mammals especially migrating via the Beringia land bridge (Siberia -Alsaka) to and from between Asia and America and via the Greenland land bridge in the early Cenozoic between Europe and America. These immigrants also must have caused ecological upheavals of their own. They would have been competition for resources and they must have brought over parasites and caused much death and destruction. We have a more guilt free dispassionate view of these faunal turnovers and extinctions. Tim Flannery has the details of these ancient exchanges that took place tens of millions of years ago and the ecological history of the America's in his excellent book The Eternal Frontier.

Charles Mann though weaves many fascinating stories of the Columbian exchange. One that caught my eye was on the impact of malaria on the institution of slavery. The climate which made the southern parts of the America's friendlier to intense plantation agriculture were also environs in which malaria thrived. Africans were more resistant to this newly introduced disease while indentured servants from Britain and Europe who were more commonly hired to work the fields in the earliest days of colonial settlement were dying off in great numbers. It made economic sense to start bringing over more Africans to work on the plantations.

The word exchange means that the movement of people, animals, plants and diseases went both ways. The damage in terms of human deaths, deprivation and societal disruption though was overwhelmingly more in the America's. I have often come across a common impression that it was technology, firepower and political and financial institutions that gave Europeans the decisive advantage over Native Americans. Those did play a role, but the factor that titled events in favor of Europeans was the evolutionary history of peoples, rather resistance or lack thereof to disease. In a strange twist of fate, Europeans benefited from both a lack of resistance to certain diseases as well as from resistance to others. A lack of resistance to malaria stopped newly arriving European poorer classes from being tied to harsh servitude in plantations in the south where malaria was prevalent. Instead resistance to malaria lead Africans into bondage. On the other hand Europeans had evolved immunity against small pox and many infectious diseases contracted from domesticated animals from time to time. Native Americans had not encountered small pox before and not having a history of animal domestication lacked immunity against animal diseases that occasional jumped hosts. They died in their millions leaving vast swathes of countryside unattended and empty for European settlers.

America though had its grotesque revenge via the potato and guano which was used as a fertilizer. Originating in Peru, the two teamed up and initiated intense potato cultivation all across Europe. Ireland especially became addicted to the potato. But the spud carried with it a fungal parasite. In the mid 1800's the potato crop all over Europe failed. More that a million Irish died of starvation partly due to the blight and partly due to Britain's refusal to divert grain to Ireland.

One last fascinating demographic titbit about the role of Africans in building North America:

..And the second thing is that what happened after the Europeans came was not so much that Europeans came, but the Africans came. The number of Africans who came to the Americas up till about 1840, 1850 far outweighed the number of Europeans. There were three Africans for every European who came to the Americas in those first couple hundred years.

GROSS: And this is because of slavery.

Mr. MANN: Because of slavery. And so the Europeans who came, like, you know, many of my ancestors in the later part of the 19th century came to landscapes that had been radically changed, but they had - and to new cities. But those cities had been built (by) African hands, the landscapes had been reworked by African hands, the boats that were going up and down the rivers were piloted by African crews. And so that - there was a tremendous change in the very distribution of the human race on the planet as a result of Columbus.

Globalization has done great things to us as a people, but it has been served up with more than its fair share of pain.

Monday, August 15, 2011

Vertical Exaggeration Of Relief During World War 1

In Google Earth you can make the landscape look more rugged and dramatic by increasing Vertical Exaggeration i.e. by increasing the vertical scale relative to the horizontal scale of the map.  It is a common technique used to bring out subtleties in topography and to accentuate  relief. 

Perspective plays an important role in our experience of relief. A dropped coin or a small object is easier to find if you lie flat on the floor and bring your eye level as close to the floor as possible. You can get the same effect by using the tilt function in Google Earth.  In his book on World War 1 To End All Wars Adam Hochschild describes one such example of vertical exaggeration or perception of relief experienced by soldiers looking out from their trenches into the open countryside:

I also went to some of these battlefields because I always love to see the places where the history that I'm writing about took place, and you learned something there too. One thing that struck me for instance, I went to a place called High Wood because one of the people that I quote in the book is an infantry officer who gives a dramatic description at one point of a very small cavalry detachment when they were having trouble taking the German position. A small cavalry detachment charged up the hill, disappeared over the brow of the hill and then were never seen again.

So I thought could I find this hill? Well, I went looking for it. I found it. What you realize when you're there is that it's not something which I walking around or you walking around today would describe as a hill. It's, you can barely see the slope in the ground and then that makes me realize that all these descriptions you read from the war of capturing hilltops and ridges and crests and so on are written from the point of view of somebody who's lying on the ground trying to stay underneath all those bullets. Just it's a useful reminder when you go to the place

Did the soldiers really perceive those hills to be larger than they were? Their perspective from ground level could have made the relief stand out but there could be a couple of other things going on. Maybe  relief was sharper during the war but in the decades after the war the landscape has been reworked intensely. Soil rearranged by farming, ditches and crevasses filled and the topography really has become mellower. There is also the soldier's psychological perception of the landscape around them. After watching their comrades being mown down in futile charges against German machine gun pickets, for those bone tired shell shocked soldiers the words hill, valley and crossing may have taken  on a more threatening meaning.  A gentle slope might seem steeper than it was, a shallow depression might appear in the mind's eye as a deep valley. When you need to cross them to reach the enemy territory they might appear to be desperately formidable obstacles.. as menacing and impassable as the enemy waiting for you in the trenches.

Listen / Transcript

Wednesday, August 3, 2011

Documenting The Urban Subsurface In India

In a correspondence with Current Science A.K. Singhvi of the Physical Research Lab Ahmedabad proposes that an opportunity is presenting itself to understand the shallow subsurface in and around cities. Urban areas are undergoing a construction boom and excavations and pits are being dug all over.

Wouldn't it be great if both government agencies and Universities start documenting the geology with the aim of creating a database useful for urban governance.  Sometime back I had mused along similar lines with regards to the aquifers underneath Pune. Large number of borewells are being drilled within and on the fringes of the city to supplement surface water supply. I had suggested that we could further our understanding of the shallow and deep aquifers by enlarging the existing groundwater monitoring programs.

Implementing this though would require embedding a certain flexibility and adaptability to how the concerned geological agencies and University departments work. I am a little pessimistic that currently our agencies may be too wedded to their working plans to deviate from their day to day job descriptions. University faculty too need to shed an insular mentality and proactively network with and develop collaborations with builders and drillers. My experience is that many are only intent on covering and finishing the "syllabus".

These new developments could be a boon for basic data collection on the shallow urban subsurface. But is the Indian geology community opportunistic enough to grab what is being offered?