Saturday, February 20, 2016

Late Antiquity Little Ice Age And Central Eurasian Empires

Of interest-

A 120-year cold spell that spanned the Northern Hemisphere during the 6th and 7th centuries was so profound that it deserves its own name, according to a new study. Analyses of tree rings from more than 150 living trees in the Russian Altai-Sayan Mountains, as well as more than 500 older trees that have fallen to the ground there, provide a complete chronicle of climate stretching from 359 B.C.E. to the year 2011. Of the 20 coldest summers in that region in the last 2000 years, 13 occurred in the 6th century after the year 536, which a recent study of ice cores has pinned down as the date of a massive volcanic eruption somewhere at high latitude in the Northern Hemisphere. Two more large eruptions (in the years 540 and 547) helped render the 540s the coldest decade in more than 2300 years, with an average temperature of about 11.8°C (53.2°F), researchers report today in Nature Geoscience. (For comparison, 2015’s global average temperature was 14.8°C, or 58.6°F.) Particles spewed high into the atmosphere by those eruptions scattered sunlight back into space, thus cooling Earth substantially, the researchers explain. The extraordinary cold spell was probably strengthened and lengthened by the resulting increase in sea ice at high latitudes, as well as an unusually low number of sunspots in the middle of the 7th century. The poor climate may been one of many factors contributing to societal changes of the era, including widespread crop failures and famines in Central Asia that may have triggered migrations from the area to China and Eastern Europe, thus helping spread an episode of plague (depicted in this 15th century painting) that originated there. The researchers’ proposed name for the event is the Late Antique Little Ice Age, a nod to the interval’s falling within the last phases of a period many cultural researchers call the Age of Antiquity.,

Paper: Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD

I am currently reading Empires of the Silk Road: A History of Central Eurasia from the Bronze Age to the Present by Christopher I. Beckwith. It is a rich and dense book on the history of Central  Eurasia,  wherein since the Bronze Age, trade between pastoralists, agriculturalists and cities essentially created and maintained the Silk Road. It was a region typified by an aggressive expansionist mentality in the elites, necessitated in part by a peculiar cultural custom of warriors and their cult, the "Comitatus".  Maintaining these loyal followers was an enormously expensive task, achieved through control over trade routes and often war booty.   In the time period of the cooling in the 6th and 7th centuries there was continued warfare between the eastern Roman Empire and the Persians (6th century) and the expansion of Turkic people westwards from the Altaic region of Siberia. In the early 7th century the disruption of Arab tribal trade and pilgrimage routes by Romans and Persians in northern regions of Arabia saw a rebellion by Mohammed of the Quraysh family who proposed a unification of the tribal peoples of Arabia into one community under one God. And in China, the 6th century saw a reunification under the Sui dynasty after a warring period known as the Sixteen Dynasties and later consolidation under the Tang Dynasty in the 7th century. The Chinese too saw internal rebellion and also warfare with frontier regions which were under the influence of steppe Mongols to the northeast and various Eurasian peoples to the west.

How much of this prolonged warfare (going on for 3 centuries) between the Romans and the Persians and the eventual demise of these two empires in the mid late 7th century, the migration and expansions of Turkic influence in Central Eurasia, the rise of Islam and the disintegration and consolidation of Chinese dynasties be blamed on climate change? I refer to Peter Turchin's meta analysis War and Peace and War: The Rise and Fall of Empires in which he argues that such social and cultural cycles follow their own internal dynamic driven by demographic changes and trends in inequality and social cohesion or "Asabiya" which is society's ability for collective action. Exogenous influences like climate change do matter. But they may simply exacerbate divisions, schisms, and cooperative ventures that were already unfolding for internal reasons. A political ideology to expand and build empires took root early in the history of Central Eurasia, from the Bronze Age horse riding Scythian nomads onward, and has been a recurring theme until recent times argues Christopher Beckwit in his book. Climate change or not, migrations, displacement of people and languages, and the rise and fall of empires has been the inevitable consequence.

Lots to think about and digest from these two books.

Monday, February 15, 2016

Stephen Jay Gould On Justice Scalia's Misunderstanding About Evolution Science

The United States Supreme Court Justice Antonin Scalia died a couple of days ago. I remembered an  essay on him written by Stephen Jay Gould. The occasion was Justice Scalia 's dissenting opinion in the 1987 case that invalidated the State of Louisiana 's "Balanced Treatment for Creation-Science and Evolution-Science Act." Louisiana was in effect arguing that "Creation Science" be put on the same footing as the theory of evolution in science classrooms.

Here is an excerpt that goes to the core of Justice Scalia's misunderstanding about what the theory of evolution seeks to elucidate:

 Justice Scalia has defined evolution as the search for life's origin--and nothing more. He keeps speaking about "the current state of scientific evidence about the origin of life" when he means to designate evolution. He writes that "the legislature wanted to ensure that students would be free to decide for themselves how life began based upon a far and balanced presentation of the scientific evidence." Never does he even hint that evolution might be the study of how life changes after it originates--the entire panoply of transformation from simple molecules to all modern multi-cellular complexity.

and a wonderful concluding passage-

   Consider also, indeed especially, Scalia's false concept of science. He equates creation and evolution because creationists can't explain life's beginning, while evolutionists can't resolve the ultimate origin of the inorganic components that later aggregated to life. But this inability is the very heart of creationist logic and the central reason why their doctrine is not science, while science's inability to specify the ultimate origin of matter is irrelevant because we are not trying to do any such thing. We know that we can't, and we do not even consider such a question as part of science.

    We understand Hutton's wisdom. We do not search for unattainable ultimates.

We define evolution, using Darwin's phrase, as "descent with modification" from prior living things. Our documentation of life's evolutionary tree records one of science's greatest triumphs, a profoundly liberating discovery on the oldest maxim that truth can make us free. We have made this discovery by recognizing what can be answered and what must be left alone. If Justice Scalia heeded our definitions and our practices, he would understand why creationism cannot qualify as science. He would also, by the way, sense the excitement of evolution and its evidence; no person of substance could be unmoved by something so interesting. Only Aristotle's creator may be so impassive.

    Don Quixote recognized "no limits but the sky," but became thereby the literary embodiment of unattainable reverie. G.K Chesterton understood that any discipline must define its borders of fruitfulness. He spoke for painting, but you may substitute any creative enterprise: "Art is limitation: the essence of every picture is the frame."

Let me add here that although the problem of the origin of life is not addressed directly by the theory of evolution, it does come under the purview of being a scientific problem. When Gould writes "we do not even consider such a question as part of science", he means specifically the theory of evolution.  Creationists would have you think that life began as some miraculous spark, a forever mysterious event that is beyond scientific inquiry. Not so. Basic chemistry is making headway in our understanding of how inanimate matter can aggregate to form self replicating entities. See this fine post by Ashutosh Jogalekar on how chemists ponder the Origin Of Life problem. 

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.