Tuesday, September 20, 2011

New York Times Profiles Richard Dawkins

The New York Times Profiles In Science series features the evolutionary biologist Richard Dawkins.

Here is a gem:

Professor Dawkins often declines to talk in San Francisco and New York; these cities are too gloriously godless, as far as he is concerned. “As an atheistic lecturer, you are rather wasting your time,” he says. He prefers the Bible Belt, where controversy is raw.

I have first hand experience explaining evolution in the Bible belt. During graduate student days at Florida State University, I used to help my advisor on Science Day at the local mall with the fossils display.  " Well.. I can't see where the intermediate fossils are between this one and that one.." ..." I can't believe that amoeba can evolve into humans" were the kind of questions we often faced.

Teaching evolution comes with a risk of extreme reaction sometimes. Richard Dawkins though labors on and has done it better than anyone else.

Monday, September 19, 2011

Geological Framework Of the Sikkim Earthquake

Everyone is calling it the Sikkim earthquake (6.8 Richter) of September 18 2011 but the epicenter plots just west of the Sikkim border in Nepal. Information about the geological framework of the region and the tectonic elements responsible for the earthquake has been limited. At the USGS website I got the following:

The September 18, 2011 Sikkim, India earthquake occurred near the boundary between the India and Eurasia plates, in the mountainous region of northeast India near the Nepalese boarder.......

The preliminary focal mechanism of the earthquake suggests strike slip faulting, and thus an intraplate source within the upper Eurasian plate or the underlying India plate, rather than occurring on the thrust interface plate boundary between the two.

I have highlighted the sentence of interest to me. It is very unlikely that the earthquake source was within the upper Eurasian plate. It was almost certainly in the Indian plate.

Below the image shows the Himalayan orogen bounded between the Himalayan Frontal Thrust to the south and the Indus Tsangpo Suture to the north. It is along the Indus Tsangpo suture that the two continents have collided and the Indian plate has dived under the Asian plate.  The location of the Sikkim earthquake is a good 200 km or so south of this zone of thrust interface plate boundary between the two.

Source of Active Faults (red lines) - Styron, R., Taylor, M., & Okoronkwo, K. (2010). Database of active structures from the Indo-Asian Collision. Eos Trans. AGU, 91(20), 0-1. doi: 10.1130/GES00217.1 and Taylor and Yin (2009). Available as a kml file at HimaTibetMap-1.1.  See this post on the Rocks and Water blog for the story about the compilation of the fault database.

I have put up below a generalized cross section across the Himalayan orogen with the red arrow pointing to the approximate geographic position of the earthquake in relation to the major tectonic boundaries.

As you can see the location of the earthquake is between the Southern Tibetan Detachment (STD), a zone of normal faulting between unmetamorphosed Paleozoic sediments (Tethyan deposits) and high grade Greater Himalayan metamorphic rocks representing the Tethyan basement and the Main Central Thrust one of the major thrust faults that brings into contact the Greater Himalayan Proterozoic high grade metamorphic rocks (Tethyan basement) with the Lesser Himalayan low-medium grade Proterozoic metamorphic rocks. These represent deformed and exhumed upper to mid crustal levels of the Indian plate. The earthquake's epicenter estimated to be at most at 20 km depth lies firmly within the Indian plate. The Asian plate is far to the north.

Since two plates are pushing into each other, the major stress regime in the Himalayan orogen is one of compressional forces. This earthquake though was likely caused by movement along a strike-slip fault where two crustal blocks slide past each other and not towards and over the other as expected in an area where compressional forces are common.

Below is a geological map of the Sikkim Nepal region. The earthquake is located quite close to the Main Central Thrust. Geologists can learn about the type of fault that caused an earthquake by an analysis of the first motions of the seismic waves generated by the earthquake being recorded at different monitoring locations. See here for a good explanation of this method. Such a focal plane solution (yellow beach ball) for the Sikkim earthquake indicated a strike slip fault oriented NW- SE. The map also plots focal plane solutions (smaller red beach balls) for few of the recent earthquake's in this region and as you can see strike slip motion is a common type of earthquake movement here.

 Source: EIA of the TING TING H.E. PROJECT, SIKKIM - RS Envirolink Technologies Pvt Ltd (large file)

Detailed analysis of the seismicity in the Sikkim Himalayan region indicates that although earthquake activity is located in the region  near major thrust faults, many earthquakes are not associated with them. Instead movements along faults like the Gangtok lineament and the Tista lineament which are  transverse to the strike of the orogen seem to be responsible for many earthquakes including the September 18 earthquake. These are north northwest trending faults. The plate motion of India into Asia along the Himalayas is in a north north- east direction. Some geologists have suggested that in this part of the Sikkim Himalayas some of the crustal shortening is being accommodated by movement along these transverse strike slip faults rather than by underthrusting.

Crustal Shortening: The upper part of the Indian plate is being crumpled and squeezed into a narrower zone. How is the crustal material accommodated in that narrow zone. Commonly by piling crustal blocks on top of each other by thrusting along faults. This leads to crustal thickening and contributes to the elevation of the mountain chain. Or sometimes by sliding blocks past each other   along strike slip faults both transverse to the orogen as in the case of this earthquake and also parallel to the orogen as is possibly happening along the two east west strike slip faults north of the Sept 18 earthquake location seen in the first image of this post.

In the past 35 years there have been 18 earthquakes in this region of magnitude 5 or greater. No doubt there will be many more in the future. Some will be along the strike slip faults described above. Others may be along the major thrust faults like the Main Central Thrust.

..and no... you won't be able to predict them. Preparedness in the form of better building construction and a functioning disaster relief mechanism is the only way to save lives.

Friday, September 16, 2011

Why The Majority Of Scientists Believe In Evolution

Came across this golden oldie at JesusandMo.net.

Callan Bentley at Mountain Beltway has very ably demonstrated that the Dunning-Kruger effect afflicts most of the U.S. Republican Presidential candidates.

New Geosciences Blog By Author Of Basin Analysis

Professor Philip Allen of Imperial College London and one of the authors of the book Basin Analysis: Principles and Applications is blogging.

Check out this great post on Dynamic Topography.

Monday, September 12, 2011

Data Problems In The Indian Geospatial Industry

Geospatial World has several articles (1, 2, 3 ) on the current state of the Indian Geospatial Industry. As I have been writing on this blog, there have been several initiatives taken by the Indian government to encourage growth of this industry. Of primary concern to users is the unavailability or slow availability of useful data.

Aditi Bahn Assistant Editor, Geospatial Media and Communications Pvt. Ltd. writes:

There is no single window where all the information can be obtained. For example, if a user requires information about topography and demography of a place, he has to approach Survey of India and Census of India respectively. The two have their own procedures in place and would provide data in their own time frame. She quotes industry specialists : 

“The overhanging issue is the availability of data under one umbrella. Information is scattered and varied and have to be collated very frequently. It has become extremely challenging,” explains Aiyer.

..and (Mr. Agarwalla) -  “Even before we talk about public-private partnership, we need to talk about public-public partnership. For most of my users, just the map or census data by itself is not good enough. So can Survey of India and Census of India partner together?”

That is not unusual. Having data in two or several different places need not by itself be a big problem. Even in countries  where spatial data is relatively freely available like the U.S, many state agencies and federal agencies have ownership of their data. Finding it though is easier by going to a central data listing like the one maintained by the U.S. National Spatial Data Infrastructure. Most government agencies who produce spatial data are registered with their NSDI and follow agreed upon data standards and data dissemination practices.

In fact it is inevitable that various central and state agencies responsible for the data will want to keep ownership of it. The Indian National Spatial Data Infrastructure (NSDI) was meant to deal with exactly this problem by issuing guidelines and standards for data creation, data storage formats and data access thereby enabling users to find and combine data from different agencies with ease. The important challenge is not whether different agencies can partner each other, but getting agencies to follow standard practices in a time bound manner. The NSDI portal would then list agency addresses to go to for your data needs.

I remember talking to a senior geologist with the Geological Survey of India in 2004. I was told that digitization of 1:1 million scale geological maps is almost done and work is going on the 1:250K and selected 1:50k series. Most of this data would be ready to go online by 2006. Five years since this self-proclaimed deadline, there is still no easy way to access geology digital data.

Why has the NSDI not been successful in getting organizations to cooperate in a timely manner?

Bad Science Is Quite Funny

I am enjoying reading Bad Science by Ben Goldacre. As the back cover promises, it offers relief from scaremongering journalists, pill pushing nutritionists, flaky statistics and evil pharmaceutical corporations. I should add homeopathy to the list. It gets a thorough drubbing too.

The book is about exposing charlatans and quacks who misrepresent or ignore science and carve out a place for themselves as health experts promising cures and interventions to enhance the quality of your life.

It is fun to read not just because it is wittily written but it is a useful exposition on how sensible people can end up believing nonsense and how you can train yourself to critically weigh evidence and sift through the mountains of (mis)information and fantastic claims that self-serving experts throw at you.

Wednesday, September 7, 2011

The Easterly Tilt Of The Deccan Plateau

A reader came across an old post of mine on the uplift history of the Western Ghats and asked:

1) What is the relationship between the Deccan volcanics and the easterly tilt of the Indian plateau (i.e. the plateau covering the Deccan volcanics and the southern Indian peninsular region)

2) Why is the northern half of the Western Ghats composed of basalt and the southern half composed of gneiss?

The region south of the Tapi river covering the Deccan basalts  and the southern Indian peninsula exhibits an easterly drainage with the rivers flowing into the Bay of Bengal. Image below shows the Indian peninsular region with easterly drainage. The Deccan Plateau (in green) is the area covered by the Deccan basalts. South of this region is Precambrian terrain. Along the east coast there are Permian-Triassic and Cretaceous basins.

Source: Sheth H.C. (2007)

The relationship between the Deccan volcanics and this easterly tilt is indirect. There are many plausible reasons for the easterly tilt of the Indian crust. ,

a) The breakup of Gondwanaland produced Permian-Triassic rift basins along what is now the eastern margin of India. Initially the sources of sediment being deposited in these basins were from the east and south i.e elevated regions now forming continental shelves of  India and the continental margins  of Australia and Antarctica. Beginning late Jurassic rifting produced the now western margin of India. This younger rifting event generated topography to the west and reversed sediment distribution patterns. The Late Jurassic and Cretaceous basins of south India received sediments from the west i.e. via an easterly drainage.

b) The rifting event that created the western margin of India also eventually triggered the Deccan volcanic episode. Post volcanism in the Cenozoic the Deccan region has titled to the east due to the Western margin undergoing uplift. This has been explained as an isostatic response to denudational unloading of the crust i.e. erosion has stripped material away from the Western margin forming the coastal plain and the steep Western Ghat escarpment. All that eroded sediment has been deposited  within basins in the Arabian sea.  This removal of weight has led to the crust rebounding and tilting in an easterly direction. The schematic  shows the development of an easterly tilt  ( east to the left) due to rift flank uplift and isostatic rebound (source: Campanile et al 2008)

c) The eastern margin of India is older (about 130 my)  than the western margin (about 65 my). The oceanic lithosphere in the Bay of Bengal is colder and denser and it is sinking and dragging down the peninsular region with it.

d) The Bengal sediment fan i.e. the pile of sediment eroded from the Himalayas throughout  the Cenozoic and deposited in the Bay of Bengal is weighing the crust down and exerting a dragging down effect on the Indian peninsular region. There is about 22 km of sediment at the mouth of the Ganges -Brahmaputra delta and about 8 km of sediment as south as Chennai.

Likely all the above have acted in combination to produce the easterly tilt.

2) The reason why the southern part of the Western Ghats are made of gneiss is that the Deccan lavas never erupted and flowed that far south. So the boundary between the basalts and the gneiss marks the southern limit of Deccan volcanism.

Tuesday, September 6, 2011

The Ganges Delta And The Hungry Tide

Amitav Ghosh is his book The Hungry Tide  evocatively describes the Ganges -Brahmaputra delta, the place where these mighty rivers change form as in from a one major active meandering channel into many entangled entities:

In our legends it is said that the goddess Ganga's descent from the heavens would have split the earth had Lord Shiva not tamed here torrent by tying it into his ash-smeared locks. To hear this story is to see the river in a certain way: as a heavenly braid, for instance, an immense rope of water, unfurling through a wide and thirsty plain. That there is a further twist to the tale becomes apparent only in the final stages of the river's journey - and this part of the story always comes as a surprise, because it is never told and thus never imagined. It is this : there is a point at which the braid comes undone; where Lord Shiva's matted hair is washed apart into a vast  knotted tangle. Once past that point the river throws off its bindings and separates into hundreds, maybe thousands of tangled strands.

Until you behold it for yourself, it is almost impossible to believe that here, interposed between the sea and the plains of Bengal, lies an immense archipelago, stretching for almost three hundred kilometers, from the Hoogly River in West Bengal to the shores of the Meghna in Bangladesh. 

The islands are the trailing threads of India's fabric, the ragged fringe of her sari, the achol that follows her, half-wetted by the sea. They number in the thousands, these islands; some are immense and some no larger than sandbars; some have lasted through recorded history while others were washed into being just a year or two ago. These islands are the rivers restitution, the offerings through which they return to the earth what they have taken from it, but in such a form as to assert their permanent dominion over their gift. The rivers channels are spread across the land like a fine mesh net, creating a terrain where the boundaries between land and water are always mutating, always unpredictable.

The delta and its front end - the sediment fan -  that is present below sea level in the Bay of Bengal is essentially made up of Himalayan sediment worn down by the many rivers and redeposited in the Bay. A pile of sediment more than 10 km thick have accumulated since the early Cenozoic.  Image below shows the Ganges Brahmaputra delta and the region called the Sunderbans named for the mangrove forests that grow on the thousands of sandbars and islands.

Friday, September 2, 2011

India Asia Collision And The Evolution Of Hindu Thought

Wendy Doniger in her book The Hindus: An Alternative History draws the following parallel between the collision of a piece of Africa (the Indian plate) with the Asian plate and the evolution of Hindu thought:

In part because of the intertextuality and interpracticality of Hinduism, one text or ritual building on another through the centuries, right back to the Vedas, scholars looking at the history of transmission have assumed that the Veda was the base onto which other things were added in the course of Indian history, just as Central Asia was the base that absorbed the impact of that interloping piece of Africa so long ago. And in the textual tradition, at least, this is true enough of the form in which ideas were preserved, the chain of memorized texts. But from the standpoint of the ideas themselves, it was quite the opposite. The Vedas was the newcomer that, like the African island fusing onto a preexisting continental base, combined with a preexisting cultural world consisting perhaps of the Indus Valley, perhaps of any of several other, more widely dispersed non -Vedic cultures. 

One can get carried away to the point of silliness comparing geological evolution of India with the coming together of cultural and religious thinking during the evolution of Hinduism. So don't take this too seriously but I couldn't resist extending the comparison a little.

One aspect that comes to my mind is the retention of the original state. All along the geological landscape of the Indian subcontinent it is easy to make out which  is the original fragment of Africa (Gondwana)  and which the original Asian plate. Over much of the Indian subcontinent the original Gondwana characters of India remained unchanged after the two continents collided as is the case with the Asian continent. They are in proximity only along a narrow zone called the Indus-Tsangpo Suture in the Ladakh -Tibetan Himalayan region. Over there the crustal blocks of the two plates, their provenance recognizable, lie next to each other along  faulted contacts, slivers of ancient Gondwana pasted onto fragments of Central Asia. The boundaries between the two are sharp. It is like as Doniger puts it components of a salad. It may appear mixed but you can recognize the greens from the nuts easily. 

The coming together of the Vedic and non-Vedic worlds has resulted in a more diffuse landscape of ideas and people. Unlike geology there is no spatial boundary within the Indian subcontinent where the Vedic world collides with the non-Vedic. You might be tempted to put this at the junction where Indo-Aryan languages give way in the south to Dravidian languages..but that boundary between the two peoples has shifted geographically and evolved over time to be more a language boundary than a boundary of ideas. Gods and cultural and social practices have flown to and fro between Indo-Aryan and Dravidian speaking people across geography and social strata. So have genes, and the result is more a milkshake than a mixed salad. 

Beyond the Dravidian speaking pariah, farmers, merchants, kings and priest, a social hierarchy likely imported from the Indo-Aryan world, there were many groups speaking Austro-Asiatic and other now extinct languages who progressively became marginalized with the encroachment of Indo-Aryan and Dravidian farming communities and city states. These were the adivasis or tribal populations who at first sight might seem to be a world apart from Vedic and mainstream Hindu thought. They would seem to resemble the discrete pieces of Gondwana and Central Asia, living in close proximity but separated from mainstream Hindus by sharp social, cultural and genetic fault lines. There is some truth to the salad bowl analogy here. But over millenia these fault lines must have been breached and boundaries blurred. Once thought to be unchanged descendants of the first migrants from Africa many tribal populations have to a degree assimilated with the Indo-Aryan and Dravidian speaking populace. Recent studies have shown substantial amounts of Eurasian and south east Asian genetic components within different Indian tribal populations.

There must have been linguistic and cultural exchanges as well.. for example many marginalized groups adopted Indo-Aryan and Dravidian languages. Going the other way it is likely that both the
elite Sanskrit literature and popular vernacular mythology borrowed from animist tribal traditions and folklore.

Within the Ladakh and Tibetan region and the Karakorum and Hindu Kush ranges though there are indicators of geological processes that resulted in the two plates not just residing side by side but forming a more complete mix. As the Indian plate subducted underneath the Asian plate, deep inside the crust, very high pressures and temperatures caused the rocks at the contact between the two plates to melt.  In that magma, elements scavenged from two different plates recombined into new minerals. The two plates created one entity.  These mixed rocks called anatexic granites form chains of plutons north of  the Indus -Tsangpo suture, the zone of collision of the two continents. 

So although the fault bounded terrain of the Indus-Tsango suture works as an analogy particularly for some marginalized groups, it is in these granites that geology comes to being the closest analogy to the evolution of mainstream Hindu thought in which ideas from the Vedic and non-Vedic worlds have come together, some traceable to their sources, others having synthesized into inseparable traditions, multiplicities within an individual.