Thursday, January 29, 2015

Darwin: An Encounter With Beetles

In 1827 Charles Darwin's father Robert Darwin, alarmed that his son was turning into  a wastrel, decided to enroll him at Cambridge with the ultimate  aim of preparing Charles Darwin for a life as a country parson. This would set him up for life among the country gentry he already knew and was comfortable with. Charles's unhappy tryst with medical school in Edinburgh had disappointed his father and the Church of England  seemed a perfect place for a rather aimless son with a love for nature and sport.

"What calling but the highest for those whose sense of calling  was nil?"

Charles Darwin mulled  over his future and was not entirely displeased. Although  he had spent two years in Edinburgh in the company of free thinkers  and religious dissenters who insisted that nature be explained in material terms and not through supernatural explanations, he still, under the considerable  influence of  his  sisters, took  religion seriously. Besides, a career in a rural parish would give him time to pursue his real  passion, which was natural history.

In Cambridge, in the company of  his cousin William Darwin Fox he became obsessed with collecting beetles.

"Nothing was spared in the trophy hunt. He bought a sweeping net and learned how to trap tiny jumping and flying insects. Sheaves if cardboard were festooned with beetles, each pinned in its proper place. He also hired a local to collect the debris from the bottom of barges  that brought reeds from the fens, which he sifted through,  hunting down his prey. It was not simple  slaughter, for some beetles had unexpected defences. One day, on stripping  bark from a dead tree, he  pinned down two rare types,one in each hand. Suddenly, he saw a third new species, too good to lose. His  action was that of a trained egg collector. He popped the right-hand one on his mouth. Unfortunately, it was a bombardier beetle,which promptly lived up to its name by squirting a noxious boiling fluid into his throat, momentarily stunning him. He spat the beetle out, losing it on the ground, and in the confusion dropped the others too". 

It was at Cambridge that Charles Darwin met John Stevens Henslow and Adam Sedgwick. From Henslow he learned botany and the methods of  rigorous scientific observation and analysis. Henslow's recommended books, especially Alexander Von Humboldt's South American travelogue Personal Narrative, inspired Darwin to travel. Henslow  also  introduced Darwin to Adam Sedgwick  from whom he learned the basic principles of geology and formed an appreciation of "deep  time", that the earth must be very old. .."What a capital hand is Sedgewick for drawing large cheques upon the Bank of Time".... This conceptual grounding proved crucial to accommodate his theories of evolution. 

Later, it was Henslow who recommended Darwin's name as a companion to Captain Robert FitzRoy who would be commandeering the HMS Beagle to a voyage of South America and beyond.

..summarized from Darwin:  Life Of A Tormented Evolutionist.

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".