Thursday, January 22, 2015

Field Photos: Basalt Landscapes Around Fort Ghangad Near Pune

Its that time of the year when I go wandering in the basalt countryside around Pune. Its always a fine day off exploring the myriad valleys and mountain ranges. Last Sunday I had gone with some friends to fort Ghangad about 80 km west of Pune, situated near the backwaters of the Mulshi  Dam.

The interactive map below shows the location of the fort and a synoptic view of the landscape and geology too (more on that later).

Fort Ghangad- A small mesa landform. You can see the ramparts at the very top.

Friday, January 9, 2015

Is The Ganga River The Longest River In The Ganga Basin?

Seems like a strange question to ask? The Ganga is no doubt the most important north Indian river in terms of its cultural and religious significance but is it the longest?

A new study published in Current Science (open access) which measured the lengths of various river segments from headwaters to their confluence with the Ganga segment and further to the mouth, finds that it is not. The honor goes to the Tons-Yamuna segments:

The length and discharge data together suggest that there exists a river within the Ganga Basin which is longer than the Ganga River by at least 370 km (Table 3). This is the segment originating from the Banderpunch Mountains (i.e. Tons River). But, is this the main stem in the Ganga basin? It is well known that the main stem of a river sets the base level for its tributaries. Therefore, we measured incision by both the Ganga and the Yamuna rivers upstream of Allahabad up to 100 km. The results showed that the Yamuna River is more incised, thus setting the base level for the Ganga River (Figure 4). This analysis further strengthens the result of the present study that the river segment in the Ganga Basin from the Banderpunch Mountains (source point S8) is the main stem. The total length of the river comes to 2758 km up to its confluence with the Brahmaputra.

Not only is the Ton-Yamuna segment longer than the Alaknanda-Ganga segment up to Allahabad (confluence of Yamuna and Ganga) but the discharge of the Yamuna is significantly more than the Ganga at the confluence.  This is because of the contribution to the Yamuna of the large Chambal river draining the Pre-Cambrian heartland of India. Of interest too is that the Chambal discharges more water than the Yamuna at the confluence of these two rivers.

This kind of work is important because:

This finding has huge implications on the geomorphic study of the Ganga Basin rivers. It would mean that the HFR (the authors have named the newly calculated longest segment as the Himalayan Foreland River for scientific purposes only) sets the base level for the Ganga River. Since several relationships are worked out with the length of a river (e.g. basin area versus stream length, discharge versus stream length, grain size versus stream length, etc.), there is a need to re-evaluate these relationships for the Ganga Basin with this length. Further, changes in these relationships can affect the predictability of river response that can in turn influence any river-related planning in the Ganga Basin.

I have one additional  comment. The authors ask :

The results also raise an important question; in spite of greater length why has this segment not gained importance? This question remains unanswered and the only possible answer could be that rivers in the Ganga Basin attained their present set-up at a much later stage, e.g. the Yamuna River is suggested to have started flowing towards east only during Late Pleistocene.

What could they possibly mean by this? Are they talking  of cultural  significance of these rivers? We are now reasonably sure  that the Yamuna started flowing along its present course as early as 50,000 years ago (1 ,2) much before any of these north Indian rivers came to be deified.

Russia's Underappreciated Contribution To The Geosciences

Nature Geoscience has a short editorial that pays tribute to Russia's scientific legacy, more specifically that in geology. Political differences and language barriers have isolated Russian science and scientific literature from the rest of the English speaking science community.

Consider this:

Lomonosov is the author of one of the most important treatises of geology that those of us who were educated in the West have probably never heard of. On the Strata of the Earth was published in 1763 and many of the ideas put forth in the book predate — by a quarter century — similar theories from James Hutton and others considered today, in the West, to be the founders of modern geology. Instead of being heralded alongside his European counterparts, Lomonosov's contribution to the geosciences has been buried, partially due to the fact that On the Strata of the Earth, like Lomonosov's other texts, was published in Russian.

One can quibble that Nicholaus Steno preceded both of  them, but the point is well made. It  is  of some urgency that Russian scientific literature be made more accessible to the rest of the world:

At this time of renewed tensions between Russia and the West over the annexation of the Crimean Peninsula, Ukraine and the risk of renewed isolation of Russian science, it is especially important that the scientific divide of language and politics be lifted so that the body of literature can grow from a stronger, united base.

read more here...

I remember a guest lecture by a Russian petrologist during my graduate student days in Pune, India. He gave an engrossing talk on retrograde metamorphism with examples from Russia and also from the early Proterozoic mobile belts (ancient orogenic mountain belts) from Central India. He loved those old  Zeiss natural light petrology microscopes our department used then (and still does!). Kept saying the mineral colors appear "natural".

Thursday, December 25, 2014

Darwin's Voyage Captured In Sketches And Watercolors

A nice article in the Guardian tells the story of Conrad Martens, an artist who accompanied Darwin for the first few years of his voyage to South America and beyond. Martens sketches and watercolors helped capture not just the lives of local people, landscapes and seascapes but shipboard and other research activity of crew and of Charles Darwin.

Now all this material has been put together in a digital archive accessible via the Cambridge University Library.

 Darwin's Christmas of 1833 with Martens drawing the activities seemed like fun times aboard the Beagle:

“After dining in the Gun-room, the officers & almost every man in the ship went on shore. – The Captain distributed prizes to the best runners, leapers, wrestlers. – These Olympic games were very amusing; it was quite delightful to see with what school-boy eagerness the seamen enjoyed them: old men with long beards & young men without any were playing like so many children. – certainly a much better way of passing Christmas day than the usual one, of every seaman getting as drunk as he possibly can.”

Its a a treat to go online and peruse through one of history's most epic voyages!

...Meanwhile  FINALLY! .. I  am in possession and eager to start Darwin- Life Of  A Tormented Evolutionist by Adrian Desmond and James Moore. I have heard and read so much about the book that I  am now afraid that I might be disappointed. Unlikely, since Darwin's life, work and times are a fascinating topic with many many treasures to mine.

Happy Holidays!

Thursday, December 18, 2014

Post Permian Mass Extinction Size Reduction In Glossopteris Plant Lineages

Mass extinctions prune away branches of the tree of life. The late Permian-Triassic mass extinction event affected marine and terrestrial animal life severely, perhaps more than it affected terrestrial plant life. One common observation is that survivor species tend to be smaller bodied representatives of groups. This is known as the Lilliput effect.

A lot of attention has been paid to evolutionary trends in size during and post mass extinction in various animal groups. An interesting paper in Current Science (open access)  documents the Lilliput effect in one of the iconic terrestrial plant groups  of Late Permian -Early Triassic times; the seed fern Glossopteris.

From the paper:

Modern day high-resolution regional palaeoecological studies have proved the myth wrong, which stated that the mass extinction event had little macroecological or evolutionary consequence for terrestrial plants The early Triassic (Panchet Formation) in India witnessed more arid or semi-arid climate in comparison to the Permian. The early Triassic experienced greenhouse conditions with a warmer phase (Figure 6) due to global rise of temperature coupled with episodes of intense volcanism. The reduced size of the lamina is one of the strategies adapted by the plants during the adverse condition in early Triassic when there was indeed a shortage of essential nutrients in the soil, in addition to seasonal dry climate, irregular rainfall and widespread aridity. The leaves possessed cuticles with sunken stomata since the atmosphere during the early Triassic had higher levels of CO2 and lower O2levels (Figure 7). The Glossopteris flora of late Permian was adapted to temperate, cool and moist environments. The phenomenon of dwarfism as evidenced in Glossopteris has been observed only up to th e early Triassic, which is represented by the Panchet Formation. During the middle to late Triassic, typical Dicroidium flora associated with Lepidopteris takes over the preceding Glossopteris flora.

Records of plant fossils substantiate the evidence that numerous physiological, reproductive and behavioural traits enabled the smaller sized plant species to persist in extreme climatic conditions.

I didn't know there was a myth that mass extinctions have little macro-ecological or evolutionary consequences for terrestrial plants. Although, I do get the impression that studies of plant evolution get less attention in the media than animal evolution.