Tuesday, October 29, 2013

What Disease Did To Europe

From The Economist : Plagued by dear labour

Most of the article is about a debate on whether the population crash due to the plague outbreaks in the mid 1300s Europe brought about real improvements in wages and labor rights.

and then this speculation:

A more speculative theory suggests that the Black Death encouraged Europeans to become more imperialistic. Prior to the Black Death, Europeans were rather averse to long sea voyages, given the extremely high death rates on boats. But as death rates on land soared, people became less afraid of sea travel; it was not much riskier than staying at home. As a result, colonialism was kick-started. Mr Belich links the plague to the “spread of Europe”.

Interesting-- i would think the more immediate reason that triggered widespread European exploration and imperialism was a desire in Christian Europe to break the Muslim domination of Indian Ocean and Arabian Sea merchant routes. With this disease theory one can argue that it was high death rates on land that made Europeans get over their timidity of sea voyages.  Another factor is that advances in ship building made long voyages less risky and produced ships big enough to make voyages profitable. Dom Henrique (better known as Henry the Navigator) the younger son of the King of Portugal in the early fourteen hundred's was asked to find a land route across the Sahara to break the Muslim bottleneck on the Red Sea and Persian Sea routes. He realized the foolishness of this venture and began collecting navigation charts of the African coasts and became a patron of ship builders. That subsequently led to explorers like Batholomew Diaz and Vasco De Gama to finally round the Cape of Good Hope and find a passage to India and the East Indies spice riches.  Again with this disease theory one can argue that disease and the population crash triggered innovation in general and one result was advances in ship building!.. so you can end up putting the disease theory at the root of any complex causal chain and explain all sorts of intangibles with it.. that makes me wary..

Wednesday, October 23, 2013

Early Homo- One Species Or Many?

A paper analyzing the variation in morphology in early Homo fossils from Dmanisi Georgia dated to about 1.8 million years ago and further encompassing East African samples too has created quite a stir. The authors conclude that the range and pattern of variability in the samples suggest that all these early Homo fossils - previously named as Homo habilus, Homo erectus, Homo rudolfensis - represent one variable species. Early Homo did not branch off into new species, rather it is one lineage.

If you want to go beyond the more sensationalistic reporting of how this changes "everything" read these two posts-

1) John Hawks - A perspective on the single species hypothesis for early Homo and what it might be really telling us about evolution, migration patterns and population characteristics of our ancestors.

2) Adam Van Arsdale- What the Dmanisi sample tell us about variation in species and how best to interpret it in the fossil record.

Thursday, October 17, 2013

Lunar Cycles And Groundwater Level Fluctuations In Confined Aquifers From S. India

Interesting paper in Current Science (Open Access) - Impact of Earth’s crustal tides on groundwater regime in confined sedimentary aquifers of Andhra Pradesh, India - Umamaheswara Rao Bollimunta

Water being less rigid deforms more easily due to the Moon's and Sun's gravitational attraction, manifested as the familiar ocean tides. However, the earth's crust too deforms slightly. So, there are crustal tides daily just like ocean tides. The magnitude of deformation is quite small, about 2 feet across the diameter of the earth. U.R. Bollimunta in this paper demonsrates that water levels in two piezometric wells i.e. wells which puncture confined aquifers show cyclical variations in water level tracking lunar phases. When the moon's pull is the strongest as on full moon the water levels drop. This is because when the moon's tidal attraction is maximum the overburden load on the aquifer is reduced allowing it to expand every so slightly.  During times of less lunar attraction the aquifer compresses causing water levels to rise again.

Fascinating stuff-


Signatures of the Earth’s crustal tides are recorded in the groundwater regime, particularly in confined aquifers in the form of rise and fall of its piezometric surface. Though this phenomenon is universal, and exists in the entire groundwater regime, the recording at a few places and in some rare situations is doubtful. An attempt is made here to study the conditions required for recording this phenomenon along with its basic principles. The Central Ground Water Board has constructed 115 piezometer wells and monitored piezometric heads with high frequency digital water level recorder. The impact of Earth tide on ground- water regime is clearly recorded at two sites namely, Kothagudem (Khammam district) and Mangapet (Warangal district). The wells at these sites are constructed in the confined aquifer of Kamthi sandstone in Godavari valley which is nearly 200 km inland from the east coast. Analysis of the data reveals that the piezometric level heads fluctuate in a cyclic manner and the variations for each lunar cycle of 13–14 days with high peaks on new Moon and full Moon days. The peaks observed in the piezometric heads gradually decline coinciding with the lunar phase. Distinct changes in piezometric heads are observed for each phase of the Moon in both of the above-mentioned places. An account of impact of lunar and solar attraction forces on piezometric level heads of ground- water, the ideal conditions required for recording this phenomenon along with a comparison of these hydro- graphs with examples from the literature are provided in the present study.

And No Astrologers.. this slight crustal expansion and compression does not cause big earthquakes.

Monday, October 14, 2013

Giosan Et Al Reply To Valdiya's Article On The Sarasvati River

You may recall this controversy which I detailed in an earlier blog post. A quick recap. A paper in PNAS by Giosan et al in May 2012 presented the results of geomorphological analysis of the Haryana and Punjab plains and concluded that there was no glacially fed rivers flowing through this region during the Holocene. This meant that the Harappan civilization in this region was being sustained by a monsoonal river system, the remnants of which is known today as the Ghaggar, identified by some as the river Sarasvati described in the Rig Ved.

Prof. K.S. Valdiya a very senior Indian geologist did not like this conclusion. Moreover, he felt that Giosan et al have not paid due respect to the work of Indian geologists working on the problem of ancient river systems of this region. He wrote a highly emotional article in Current Science in which he misattributed sentences which I had penned on my blog to Giosan et al and also misrepresented (in my opinion) the work of Giosan et al and other workers.

Both Giosan et al and I complained about the misattribution to Current Science to which Valdiya gave brief unsatisfactory replies.

Now Giosan et al have published a second reply in which they clarify the scientific queries that Valdiya had raised.

Here it is - Open Access.

I find it puzzling that the original paper came out in PNAS, but Valdiya chose to comment and complain - not as tradition expects in PNAS - but in Current Science.

He also has not replied to Giosan et al's second clarification.

Monday, October 7, 2013

Found It! Memories Of Early Days Of Geology Education

A mouse got in to an old book shelf a few days ago. Panicky cleaning up ensued and there from the back out came a treasure.. (not the mouse.. it ran away)

This well worn copy of the Petrology classic was my introduction to rocks when I started taking geology classes during my first year B.Sc. The book written in the late 1920's was still being used in the mid late 1980's and early 1990's! There were about a hundred of us packed in the intro geology class with the instructor drawing rough sketches on the black board and explaining the basics of the interior of the earth and the three primary types of rocks, igneous, sedimentary and metamorphic.

I quickly gave up of Tyrrell and turned to other sources.. but those afternoons I do remember.. I knew that after two years of high school not knowing what I was going to do in life that I was on to something special. Geology has stayed with me ever since.

My decision to take up geology had interesting reactions from family and friends. My immediate family, mom, dad, sister and my grandfather completely supported me. Others were less convinced. I was not very good at math so engineering was out. I was not very good at biology so medicine was out. These two were the prestige courses for students.. they had high social standing and these degrees lead to high income careers. Taking a degree in pure sciences was basically admitting that you hadn't done well in the exams and thus could not hack it in the tough technical degrees.

Getting a B.Sc was for the duffers. But my relatives could not say that to me. So they were very sweet about it.." Geology?.. Yes you should take it.. someone has to do it..  we need oil.. minerals"... blah blah blah..

This condescending attitude continued until I got a scholarship to go to the U.S. Then snobbery took over. Getting scholarships to the U.S was again something that mostly only students from technical colleges like the IIT's were supposed to be successful at. Suddenly I was on par with them. Support for me was now because I had at last brought some prestige to the extended family.. "my nephew got a scholarship to the U.S... for a PhD"..

That I had really become passionate about geology and it meant to me more than scholarships and going to the U.S. completely escaped them.

Friday, October 4, 2013

Quote: John Dewey On The Armchair Geologist

John Dewey in his review of Colliding Continents - a book about the geological evolution of the Himalayas by Mike Searle has these harsh words-

Reading a book like this makes one realise how shallow and limiting is the pseudo-geology done by those who sit in front of their computers composing drivel. As Francis Pettijohn remarked, ‘the truth resides in the rocks’ and that ‘there is nothing as sobering as an outcrop’. This work is a useful lesson to those who are not prepared to sweat and get tired and dirty and try to find out the message of the rocks.

Hard to argue against - but computer modeling when the inputs are acquired through hard fieldwork is a powerful tool to understand geological processes. John Dewey refers to the idea of middle crustal extrusion in Himalayan mountain building. This idea suggests that the rocks making up the High Himalayan Crystalline Series were initially a weak viscous middle crustal layer sandwiched between a strong upper crust and a strong mantle. These soft crustal rocks formed during the India-Asia collision and then were squeezed southwards and as denudation started removing the upper crust were extruded i.e. brought to the surface from underneath Tibet. This idea to be refined and to mature has required all possible ways of understanding the earth- fieldwork, high tech geochemistry, geophysical survey and .. yes... the computer geek... doing mathematical modelling.