Monday, July 6, 2015

Monsoon Trekking Season Is Here

I hereby declare the Deccan Volcanics Western Ghat 2015 monsoon trekking season officially open!



That picture is of the steep slopes of Fort Rajgad about an hour's drive from Pune, taken a couple of years ago.

Last year the geology highlight of my treks into the Deccan Basalt countryside was this dyke with horizontal columnar joints near the summit of Fort Ghangad.



Columnar joints are cooling cracks which develop perpendicular to the cooling surface. In lava flows, the cooling surface is mostly horizontal and so the result is vertically oriented, often hexagonal shaped columnar  joints.  In this case, the cooling surface was the near vertical contact between the intruding hot magma and the colder older lava flow. The cooling cracks therefore are horizontal.

I will be posting more pictures from this year's trekking season. The Western Ghats in the monsoon and the winter are a sight to savor!

Sunday, June 21, 2015

Cartosat 1 DEM- Two Strike Slip Faults

My two favorite strikes slip faults in India as rendered by Cartosat 1 Digital Elevation Model-

1) Yamuna Left Lateral Fault-



Source: Cartosat 1 DEM National Remote Sensing Center, ISRO

You can see that the Siwalik hills are breached by the Yamuna and dislocated in a left lateral sense, i.e. one would have to turn left to follow the narrow marker rock bed across the fault.

From a previous post on this fault-

Miocene onwards a thick wedge of fluvial sediments filled up a foreland basin that formed in front of rising thrust sheets uplifted along the active Main Boundary Thrust (MBT). That phase ended about 0.5 to 1 mya.

This fluvial wedge over the last half a million years has been deformed into the Siwalik mountains. These mountains form broad synclines and tight anticlines cut by north dipping thrust faults, a result of the continuing compression of the sediment wedge. The southernmost of these thrusts which brings into tectonic contact the anticlinal Frontal Range of the Siwaliks over the alluvial plains in called the Himalayan Frontal Thrust (HFT).

The HFT is broken into segments and the amount of displacement along these segments or thrust blocks is unequal. For example the blocks west of the Yamuna and east of the Ganga have moved southwards with an opposite sense of movement relative to the central block known as the Dun block. To view this, turn on labels and pan southeastwards in embeddable map below until the town of Haridwar where the Ganga enters the plains.

Thus the Yamuna fault has a left lateral sense of movement while the Ganga fault has a right lateral sense of movement. These faults can be thought of as lateral ramps of the HFT accommodating the displacement caused by the southwards movement of the HFT blocks. 

Structural considerations indicate that during the last 0.5 my there has been about 8 km of displacement along the Yamuna and Ganga faults, a slip rate of approx. 16 mm year. - See more at: http://suvratk.blogspot.in/2010/12/remotely-india-3-left-lateral-yamuna.html#sthash.H9K4tfrI.dpuf
 Miocene onwards a thick wedge of fluvial sediments filled up a foreland basin that formed in front of rising thrust sheets uplifted along the active Main Boundary Thrust (MBT). That phase ended about 0.5 to 1 mya.

This fluvial wedge over the last half a million years has been deformed into the Siwalik mountains. These mountains form broad synclines and tight anticlines cut by north dipping thrust faults, a result of the continuing compression of the sediment wedge. The southernmost of these thrusts which brings into tectonic contact the anticlinal Frontal Range of the Siwaliks over the alluvial plains in called the Himalayan Frontal Thrust (HFT).

The HFT is broken into segments and the amount of displacement along these segments or thrust blocks is unequal. For example the blocks west of the Yamuna and east of the Ganga have moved southwards with an opposite sense of movement relative to the central block known as the Dun block. To view this, turn on labels and pan southeastwards in embeddable map below until the town of Haridwar where the Ganga enters the plains.

Thus the Yamuna fault has a left lateral sense of movement while the Ganga fault has a right lateral sense of movement. These faults can be thought of as lateral ramps of the HFT accommodating the displacement caused by the southwards movement of the HFT blocks.

Structural considerations indicate that during the last 0.5 my there has been about 8 km of displacement along the Yamuna and Ganga faults, a slip rate of approx. 16 mm year.


The Digital  Elevation Model also brings out beautifully the Quaternary alluvial fans with tiers of river terraces deposited in the valley between the Siwaliks and the Lesser Himalayas and the intricate drainage on the southern slopes of the Siwalik frontal range.

2) Gani Kalava Fault-

This too has a left lateral movement and has a prolonged history of being reactived during different phases of sedimentation in the Proterozoic Cuddapah Basin of south India.  I  did my M.Sc dissertation on this area, concentrating on the asymmetric anticline with a gentler dipping southern limb and a nearly vertical dipping northern limb located south of Gani village.


Source: Cartosat 1 DEM, National  Remote Sensing Center, ISRO

From a previous post on this fault-

The feature is an ENE plunging asymmetric anticline with spectacular dip slopes of quartz arenites making up the southern limb of the fold and left-lateral movement along a regional fault steepening the northern limb of the fold. There is some copper mineralization along the fault. The Cuddapah basin is an intra-cratonic basin which was filled up in several depositional mega cycles. Sections of two of these mega cycles are exposed in this area. The older mega cycle comprising the Cuddapah subgroup is exposed in the core of the anticline. An angular unconformity separates the older cycle from the younger Kurnool cycle (sub group) which is exposed along the limbs.

Brown arrows shows the offset marker beds (grey arrows show sense of movement) of the oldest sedimentary formation of the Cuddapah basin, the early Proterozoic Gulcheru Quartzites and Vempalle limestones of the Papaghani Group. These lie unconformably on the Archean Peninsular  Gneiss which is the fawn colored peneplain in the left part of the DEM. The very distinct dip slopes of  the Gani anticline (south of Gani village) are made up of a much younger sedimentary unit, the Banganpalle  Quartzites of the Kurnool Group. They were deposited in energetic shallow seas, forming a vast sand shelf, wherein waves and currents winnowed out unstable minerals, leaving behind a nearly pure well sorted and rounded quartz sand. The quartz grains are polycyclic, meaning they show evidence of being derived by weathering of older sandstones, the most likely source being the Gulcheru Quartzites.

Remember this is a Digital Elevation Model,  same color means the same altitude range and not mineral composition.

Thursday, June 11, 2015

Chimpanzees Cooking

What do you have to say to this statement by psychologist Felix Warneken ?

“The logic is that if we see something in chimpanzees’ behavior, our common ancestor may have possessed these traits as well. If our closest evolutionary relative possesses these skills, it suggests that once early humans were able to use and control fire they could also use it for cooking.”

I would say that one has to be very careful in drawing general implications about ancestral abilities from the behavior of chimpanzees. They are not some frozen Pliocene ape. The human-chimpanzee split from our common ancestor may have occurred 7-8 million years ago. Since divergence,  the lineage that led to chimpanzees has been evolving for the same amount of time as our lineage. Many aspects of modern chimpanzee behavior may not reflect the ancestral condition but instead may have evolved later in their evolutionary history.

What the study that is described in the Guardian shows is that chimpanzees prefer cooked food to raw food and have abilities to defer instant gratification for later preferred reward. This though need not be restricted to cooked food. You could conceivably show that they for example behave the same way if given a choice between a raw and a ripe fruit. Or for that matter something not to do with food at all. There is no evidence that chimpanzees throw raw meat in natural forest fires and come back and eat the cooked meat. Awaiting for cooked food does not mean they posses "most of the intellectual abilities required for cooking"

And nor did our very early human ancestors. One implication drawn from these chimpanzee "cooking" experiments is that our ancestors may have developed a taste for grilled meats early on (possible) and the timeline for cooking may have to be shifted to an earlier date. I don't see the latter connection at all. The oldest confirmed evidence for cooking is about 1 million years ago, although some scientists like Richard Wrangham based on changes in physiology (larger brain, smaller molars)  seen in the fossil record push it back to around 2 million years ago.  Even assuming that the chimpanzees preference for cooked food reflects the ancestral state, one can't draw a connection between that and cooking appearing earlier in our lineage. It took 4-5 million years after our lineage split from the chimpanzee for us to evolve the ability to control fire and the addition of deliberately cooked food as part of our regular diets. That is hardly "early". It took a long time, in fact cooking has been absent for most of the time of our lineages existence, and it was contingent on a host of other unique changes in our cognition, social evolution and our abilities to use our limbs to manipulate objects.

There was nothing inevitable about it.. one just has to look at the chimpanzees. In fact, this precaution taken during the experiments gives the game away-

“Originally we thought of setting up a camping cooker in their sleeping area, but you could imagine them getting hold of a gas tank or burning themselves,” said Warneken. “This was not a viable option.”

It was not a viable option because chimpanzees don't even come close to possessing most of the required abilities to cook.

That is one of the problems of drawing sweeping evolutionary implications about behavior from contrived experimental situations.  They just don't bear any resemblance to behavior in the natural state.

Thursday, June 4, 2015

Free Download- Cartosat 1 India 1 Arc Sec Digital Elevation Model

I've been writing periodic updates on Bhuvan and have been critical about some of its features before. Today I sing its praise.

Bhuvan is the Indian Space Research Organization's web mapping portal. It was  launched with much hype in 2009, touted by the media as a Google Earth killer.  That it hasn't turned out to be. Google Earth /Maps is still the most used application for browsing imagery and exploring the world's surface.

This need not have been portrayed by the media as a Google versus Bhuvan competition. I always felt Bhuvan would offer real value by making available India specific natural resources and earth science datasets to overlay imagery. That in fact is the direction Bhuvan has been evolving for the past few years.

Bhuvan now offers a variety of  India datasets for overlay, analysis and download. I have been playing around with the Digital Elevation Model (DEM) derived from Cartosat 1 stereo imagery. The DEM is available as 1 degree tile corresponding to the Survey of India topo map sheets. The interface  to  select and download the DEM is easy to use. Technical documentation of the DEM is also available. Spatial resolution is 1 Arc Sec, which corresponds to around 30 meters. The vertical margin of  error is about 8 meters. Analysis shows that the Cartosat DEM compares well with other widely used DEM such as SRTM (90 m res) and ASTER (30 m res).

Below is  a Digital Elevation Model of the Nallamalai Hills in Andhra Pradesh with a 0.5 deg graticule overlain. I've generated this representation in Manifold GIS. The geological terrain is part of the Proterozoic Cuddapah Basin. Remember, the color scheme assigned to the DEM is not demarcating different rock types but elevation ranges. However, as a nod to the prominent geological feature that I wanted to highlight, I have assigned a color of the common rock in outcrop. These are the Bairenkonda Quartzites and Sandstones of the Nallamalai Group which form folded ridges, part of the Nallamalai fold belt. The green low relief areas are mostly underlain by shales and limestones.

And check out the drainage in color black (lowest elevation). You can make out the drainage divide between the Godavari and Krishna basins. In the upper right part of the image, streams are draining north towards the Godavari river. In the left lower part of the DEM, streams are flowing south towards the Krishna river.



Source: Cartosat 1 DEM, National Remote Sensing Centre, ISRO

I'm planning to tell more stories about Indian geology using these DEM 's. For that I  have to thank ISRO for making this dataset available.

Tuesday, May 26, 2015

Geological Monuments Of India

Well well, this is something I noticed only recently... you will see on the Geological Survey of India website (when it finally uploads) an interactive map showing sites of geological importance.  The GSI has declared these sites National Geological Monuments and has taken on the responsibility of the protection of these sites as well as their promotion for tourism purposes.

Here is the site map of the geological monuments:


Source: Geological Survey of India

And the list:

Fossil Parks:
1) Marine Gondwana Fossil Park (Gondwana basins Eastern India)_2) Fossil Wood Parks ( Tamil Nadu and Jaisalmer Rajasthan) 3) Siwalik Fossil Park  (Himachal Himalaya Foothills) 4) Stromatolite Parks (Proterozoic of Rajasthan)

Rock Monuments:
1) Peninsular Gneiss (near Bengaluru south India) 2) Columnar Basalt (Coconut Island Deccan Basalts near Udupi coastal Karnatak) 3) Pillow Lava (Chitradurga, Karnataka) 4) Pyroclastic Rocks (Kolar, Karnataka) 5) Nepheline Syenite ( (Ajmer district, Rajasthan) 6) Barr Conglomerate (tectonically stretched pebbles, Pali district, Rajasthan) 7) Welded Tuff (Jodhpur district, Rajasthan) 8) Charnockite (near Chennai, Tamil Nadu)

Geological Marvels:
1) Lonar Lake (Maharashtra) 2) Eddy Current Markings ( Panchmahal district, Gujarath) 3) Natural Arch (Chittor district, Andhra Pradesh) 4) Sendra Granite (Pali district, Rajasthan)

Monuments of Stratigraphic Importance:
1) Eparchaean Unconformity, Tirumala Hills Andhra Pradesh representing a time gap of about 800 million years between the Archean and the overlying Proterozoic
2) Jodhpur Group – Malani Igneous Suite Contact, Jodhpur District, Rajasthan- Contact between volcanic rocks and sandstone
3) Great Boundary Fault at Satur, Bundi district, Rajasthan- Faulted contact between the Aravalli terrain and the Vindhyan basin sediments

Monuments of Economic Significance:
1) Laterite in Angadipuram, Malappuram district, Kerala
2)  Bedded Barytes of Mangampeta, Cuddapah district, Andhra Pradesh
3) Gossan, Rajpura – Dariba, Rajsamand District, Rajasthan- Gossan is a weathered zone formed by oxidation of sulphide  ores.

I would add a few more to these-

1) Western Ghat Escarpment, Maharashtra- how can you ignore the spectacular 1000 feet plus basalt escarpments overlooking the coastal plains leading up to the Arabian Sea? choose any site along the sinuous edge of the Deccan plateau. In the USGS Digital Elevation Model to the left the sharp topographic divide between the darker green coastal plain and the pastel plateau shows up clearly.

2) Chambal River Badlands- Sinister looking and rich in bandit lore, these Quaternary landforms along the Chambal  river in Madhya Pradesh offers lessons in Quaternary climate change and river landform evolution.

3) Bhedaghat Marble Cliffs - Near, Jabalpur Madhya Pradesh. I am surprised the GSI missed including this, as it is already well known. These Proterzoic marble cliffs with the Narmada river flowing between is a great spot to visit.

4) Cretaceous fossil beds around Ariyalur , Tamil Nadu- scores of invertebrate palaeontologists have gotten their PhD training here. Ammonoids, echinoids, bivalves, plant leaf imprints, coral reefs... marine life that inhabited the Cretaceous seas. Some sites must be preserved.

5) Main Frontal Thrust- Chosen site along  the Siwalik Front Range- what better way to explain plate tectonics, the geodynamics of the Himalayas and earthquakes than by showing the active fault zone along which the convergence between India and Asia is being accommodated?

I am sure there are many more which geologists working in different  regions of India feel are worthy of protection.  A palaeontologist working with the Agarkar Research Institute in Pune told me that they are petitioning the GSI for protection of many more fossil sites in Gujarat. I hope the GSI extends their list to include recommendations from outside experts.

I also hope they take professional help in advertizing these monuments. Some of the choices seem a bit esoteric to me. I mean... I really can't imagine people flocking to see a "nepheline syenite intruding an antiform". Unless there is a spectacular exposure of folded strata. In which case it should be advertized as such. .. And "Penisular Gneiss"...why not point to the wonderful delicately balanced (that look as if they might topple  over any minute) granite boulders that dot the landscape around many south Indian cities like Bengaluru and Hyderabad? A few could be made into rock parks and protected from the ever consuming urbanization.

Its time also for the GSI to  rachet up its  science outreach programs. Maybe they can invite National  Geographic or Discovery Channel to make  a program on  geological monuments involving experts from Universities and the GSI. And the many regional GSI offices could develop more proactive, well advertized community outreach programs with more use of social media, geology day interaction with scientists and field trips. Educating the public has many dividends. After all, why should opinions on what should be protected be a top down phenomenon? An interested well informed science loving community could put pressure too for the protection of the many geological wonders of India.