Thursday, February 11, 2016

Book- Landscapes And Landforms Of India

Landscapes and Landforms of India ed. Vishwas S. Kale 

This is a much needed compilation by different experts of the varied geomorphological provinces of India. Every university and college in India should get a copy.

Review - Landscapes and Landforms of India by L.S. Chamyal of the University of Baroda.


Saturday, February 6, 2016

Field Photos- Deccan Volcanics- Buttes And Rubbly Flow Tops

Last Sunday I went for a short trek to Tail Baila, a basalt rock feature about 80 km west of Pune on the Mulshi dam backwaters road from Nive village to Lonavala. Take a look.


This is a "butte". It was once an extensive lava flow (s), but weathering and erosion has removed much of the extensive volcanic plateau to leave behind remnants like this , poking up like skyscrapers.


This is an edge view of the butte. Believe me it is scary when you finally come near it. It is a popular spot for hardened rock face climbers and in fact that Sunday there was a team of climbers which had made their way up to the very top.

These features are not common all over the Deccan plateau. I had put up a satellite image some time back. Here it is below again.


This region close to the Western Ghat escarpment is fractured by N-S and E-W oriented systems. Over eons, weathering and erosion along these weak planes has removed rock material and slowly fragmented the plateau in to a series of mesas, buttes and pinnacles.

On the outcrop scale too are interesting features. Here is a lava flow with a brecciated top.

 
This happens when a crust forms on newly erupted lava. As the lava moves, the crust breaks into a rubbly (breccia) upper layer. Taking a broad picture, geologists have found that these kind of lava flows with rubbly tops are more common in the upper stratigraphic formations of the Deccan volcanic pile and might be indicating more voluminous eruptive episodes and rapid expulsion of volatiles from the lava. The buttes and mesas and pinnacles of the region I having been trekking in fall in this stratigraphically upper part of the Deccan Province (see fig. on left, credit K. Canter AGI), somewhere I am guessing in the Khandala to Bushe Formations.

Better geo-chronology of  the Deccan eruptive history is now strongly suggesting several phase of eruptions with a low voluminous early phase from about 69 mya to 66 mya, followed by a high voluminous phase beginning around 66.3 mya and lasting for 750,000 years in which about 80% of the Deccan Province lava was erupted. This continental volcanism  lasted for 4 million years, but the lava pile I live on around Pune and seen in the spectacular cliff sections of the Western Ghats all erupted in a relatively smaller energetic time period of about half a million years or so. Its still a long long time from a human viewpoint. Since then, for the last 60 million year or so, the province has been eroding slowly to form the landscape we see today, the deep valleys, the mesas, plateaus and pinnacles. Imagine the enormous amount of rock broken up and material removed to form this landscape, streams and rivers carrying the derived sediment in solution and as clay particles to the Arabian Sea and the Bay of Bengal.

It has been a really glorious winter in the Deccan Volcanic Province. Monsoons have their own beauty, but winter with its brown and earthy grass meadows, bright pink blooms and black rock make for some stunning views as well.


Tuesday, January 26, 2016

History Of India Land Use Changes- 1880 To 2010

Notable Effort:

In India, human population has increased six-fold from 200 million to 1200 million that coupled with economic growth has resulted in significant land use and land cover (LULC) changes during 1880–2010. However, large discrepancies in the existing LULC datasets have hindered our efforts to better understand interactions among human activities, climate systems, and ecosystem in India. In this study, we incorporated high-resolution remote sensing datasets from Resourcesat-1 and historical archives at district (N = 590) and state (N = 30) levels to generate LULC datasets at 5 arc minute resolution during 1880–2010 in India. Results have shown that a significant loss of forests (from 89 million ha to 63 million ha) has occurred during the study period. Interestingly, the deforestation rate was relatively greater under the British rule (1880–1950s) and early decades after independence, and then decreased after the 1980s due to government policies to protect the forests. In contrast to forests, cropland area has increased from 92 million ha to 140.1 million ha during 1880–2010. Greater cropland expansion has occurred during the 1950–1980s that coincided with the period of farm mechanization, electrification, and introduction of high yielding crop varieties as a result of government policies to achieve self-sufficiency in food production. The rate of urbanization was slower during 1880–1940 but significantly increased after the 1950s probably due to rapid increase in population and economic growth in India. Our study provides the most reliable estimations of historical LULC at regional scale in India. This is the first attempt to incorporate newly developed high-resolution remote sensing datasets and inventory archives to reconstruct the time series of LULC records for such a long period in India. The spatial and temporal information on LULC derived from this study could be used by ecosystem, hydrological, and climate modeling as well as by policy makers for assessing the impacts of LULC on regional climate, water resources, and biogeochemical cycles in terrestrial ecosystems.

See this comparison


Source: Tian et al. 2014

The massive increase in cropland density over the Indo-Gangetic plain and the diminishing of forest over the Himalayan belts, Central India and Western Ghats is brought out starkly. The forests of the north east though appear to be in a better shape somewhat than other parts of India.

The paper makes a good point that deforestation was higher during colonial times and early days of Independence. The British saw forests as a resource to be exploited, a legacy that continued  after Independence as well. Post 1980's, Forest protection policies did put the brakes on massive deforestation. This however hides some details. Two year surveys of forest cover and forest health by Forest Survey of India reveals that denser canopy forests are being degraded, prime forest land continues to be diverted for development, and the band aid and balancing the book trick that is known as compensatory afforestation is not always meeting its goals and occasionally ends up causing more damage to the environment.

The article comes with lots of details about methodology used and a good reference list.

Open Access

Sunday, January 24, 2016

Papers- Geochemistry Of Carbonate Diagenesis

Aladin's cave has opened up! (behind pay wall)

This is for students and researchers in sedimentary geology and particularly those studying carbonate sediments. The journal Sedimentology has compiled a virtual collection of  papers from the past few decades on the geochemistry of various aspects of carbonate diagenesis ranging from impact of sea water composition and sea level changes on broad patterns of diagenesis to how crystal shapes and sizes are controlled by chemistry of fluids and micro-scale roughness of constituent sediment to oxygen and carbon isotope studies of grains and cements and what they tell us about the past groundwater systems and their interaction with rock material during sea level falls. I read some of these papers during my PhD research, especially some of the classic early work on stable isotope analysis of Pleistocence and Holocene carbonate sediments and rock from the Caribbean and the Bahamas.

One bad miss though - The Great Barrier Reef- A 700 000 Year Diagenetic History. I wrote a post on it some time back. It uses stable isotope and minor element analysis to understand how the Barrier Reef sediments have, through the Pleistocene, interacted with sea water and fresh water (during periodic sea level falls) and transformed in their physical and chemical composition. One can draw surprisingly broad inferences about the regional geological setting from chemical patterns imprinted in carbonate sediments, such as, the thickness and extent of groundwater systems, the paleo-topography, the paleo-climate and the role of surface vegetation in enhancing chemical reactions.

Diagenesis transforms sediment into rock. This is a great reference collection about this fundamental process of rock formation in carbonate environments.

Tuesday, January 12, 2016

5300 Year Old Iceman's Bacteria Genome Does Not Support Out Of India Theory

The genome of bacterium Helicobacter pylori found in  the stomach of the 5300 year old European mummy named the "Iceman" shows close similarity with Helicobacter pylori strains found in the gut of north Indians. This finding published in Science has been used as evidence to support the Out of India theory, which proposes that the Aryans and the Indo-European language family originated in India. One branch of it spread into Europe, diverging into various IE languages, while the branch which remained in India became the common  ancestor of Iranian and Sanskrit. A later migration into Iran founded the Iranian branch of the IE family.

Here is a tweet by Subhash Kak, one of the proponents of the Out of India theory.



He and others who use this finding of the bacterial genome to support this scenario are wrong.

Here's why.

Their scenario requires the European strain of Helicobacter pylori to have been derived from the Indian strain. That means people from India migrated  into Europe in the Neolithic-Early Bronze Age around five to six thousand years ago carrying with them the Indian bacterial strain which then evolved into the European variety found in the Iceman. This interpretation is demonstrably wrong. The analysis of the bacterial genomes clearly shows that the Indian strain shares ancestry with the European strain

" The resulting linked co-ancestry matrix (Fig. 4) showed that the ancient H. pylori genome shares high levels of ancestry with Indian hpAsia2 strains (Fig. 4, green boxes), but even higher co-ancestry with most European hpEurope strains".....

... "Furthermore, our co-ancestry results indicate that the Iceman’s strain belonged to a prehistoric European branch of hpAsia2 that is different from the modern hpAsia2 population from northern India".

In plain English what this mean is that the European strain has not evolved directly from the Indian strain.  Rather, the European strain and the Indian strain share an Asian common ancestor. This is clearly seen in the phylogeny (evolutionary relationship) presented in the supplementary materials of the  paper (page 50 of 88). See the image below.


Source: Supplementary Materials Maixner et al. 2016

The red arrow points to the common ancestor of the Iceman and Indian strains. The Iceman's strain and the Indian strain are sister lineages. The European strain is not derived from the Indian strain. The most sensible explanation of this finding is that from a common Asian source in the Anatolian / Near East region this bacteria spread into Europe and into India with the Neolithic expansion of farmers. It then diverged into the respective strains seen in the Iceman and in extant Indians. In Europe, this Asian derived strain then mixed with an African variety due to a migration in more recent times.

No evidence can be  found for a bronze age Out of India migration of people and languages from this study of the Iceman's bacterial genome.