The Aesthetics and Chemistry of Petrified Forests

Someone can observe a fair number of sunrises without becoming jaded. There is often an unprecedented observable variation in the pattern and thickness of clouds, which changes the corresponding array of colours. Add to it the sense of scale and the feeling of rejuvenation with every dawn, and each sunrise has the potential of inspiring a line like Cat Stevens’ “Morning has broken like the first morning”.

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Petrified Forest National Park (pic by the author)

So far I have only walked through Arizona’s Petrified Forest once, but I cannot imagine being jaded from repeated hikes. Almost every log of stone appears unique, and its perception, as every good photographer realises, is influenced by lighting conditions. Touching them is not monotonous either. In some petrified wood, the ends of the logs are rugged; in others the mineral has been cleaved, as if by a blade. In others, the ridges and the grain of the original tree are preserved.

And what intensifies the sense of wonderment is the mechanism that created these masterpieces of natural history. Remarkably the first rigorous laboratory study was only published recently in May of 2016. As the authors Marisa Acosta and George Mustoe pointed out, prior to their research explanations of petrified wood’s colour were derived from an unpublished analysis of limited rock samples and from speculation.

Education and Exhibitions
The Earth at the time of the late Triassic. Image from the Australian Museum

The story of Arizona’s petrified wood started about 225 million years ago during the Late Triassic period, when all land was part of a splitting Pangaea, when dinosaurs and large reptiles dominated. Flowering plants had not yet evolved, so there were no poplars, maples or palo verdes, Arizona’s national tree. Cacti, also being angiosperms, had not arisen either, and they would not have lived there anyway because the land within present-day Arizona was then a lush subtropical forest filled with the ancestors of present day conifers. In one area, these clung to eroding riverbanks and the trees fell into streams. Buried in flood plains, they were out of contact with oxygen. Anaerobic conditions slowed their decomposition. That in itself would not have been sufficient for petrification (the process of turning into stone without seeing Medusa’s head 🙂 . There was a lot of volcanic ash nearby, which introduced silica into the ground water,probably in the form of Si(OH)4. With the cell walls still intact, their cellulose and lignin (components of wood) had an affinity for silica. How the silica(quartz) formed chemically from Si(OH)4  is a mystery so far because the process has not been replicated in the lab.

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This is the process believed to occur in diatoms that deposit SiO2 particles. Whether something similar occurs during petrification is not clear.

Then the intracellular spaces also filled with the same quartz mineral. But there wasn’t just one single episode of permineralization. As we shall see, a given sample’s varied oxidation states of iron in the silica suggest that the solidifying wood was exposed to penetrating solutions exposed to different environmental conditions over the course of time.

It was previously believed that ions of copper, chromium, manganese and aluminate were responsible for the assortment of colours in petrified wood. But the authors collected over 30 samples from 3 sites in Arizona, including the Petrified Natural Park and also from Nevada, Oregon and Zimbabwe. Using a petrographic machine they prepared 200 um slides and then used Laser Ablation Inductively Coupled Plasma Mass Spectrometry(LA-ICP-MS) to identify the key impurity colouring the silica. The technique is highly sensitive in identifying elements directly on solid samples. Using LA-ICP-MS they began by focusing  a laser beam on each thin rock sample to generate fine particles. The ablated particles were then transported to the secondary excitation source of the ICP-MS instrument for digestion and ionization of the sampled mass. The excited ions in the plasma torch were finally sent to a mass spectrometer detector for elemental analysis.

Rainbow patterns in petrified wood especially were believed to be caused by a variety of metal ions. But iron alone was the key to the hues of red, purple and yellow. Strangely iron and not chromium was also responsible for the green colour in 1/3 bright green samples and in ¾ of dark green rocks. It’s already known that both abiotic and biotic pathways can reduce the +3 state of iron in ferric oxyhydroxide minerals to a +2 state to produce green rust or fougerite( Fe2+ 4 , Fe 3+ 2 (OH)12 CO3.3 H2O). Those of course are the actual minerals involved in the green parts of petrified wood. But the fact that the different oxidation states of iron in red and green minerals coexist in the same rock sample suggests that permineralization is not a one-shot deal. The following graph reveals how combinations of pH and exposure to the atmosphere influence the electron-ripping (oxidation)or electron-donating abilities (reduction) of solutions. The latter is measured by Eh, a solution’s oxidation potential. As the Eh changes over time, it could use different events to precipitate a different colour in the same log, even if iron is involved in both cases.ehph

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Petrified wood from the Long Logs Loop Trail (photographed by the author)

One will also notice abstract art–like patterns in the petrified wood. The authors describe a number of physical processes at work. These include diffusion, dilution, and a form of natural chromatography. The black parts, contrary to the previous speculation, are not due to the presence of manganese, as revealed by the analysis. Total absorption of light by the silica structure could be one cause, or in some cases small amounts of persistent organic matter were responsible.

The Petrified Forest is in essence a nature-made museum of art, history and geochemistry.

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Where is the Derivation, Dude?

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All over the internet and even in the graffiti of underpasses, we are seeing more of science’s and mathematics’ iconic formulas advertised as never before.  On the surface they seem comforting to aficionados, but are they really making the public more likely to delve into the fields?

Anyone can use a hammer, so to a society, the knowledge and skill needed in making one is more important than the skill involved in using it. Similarly anyone— even computers– can plug numbers into mathematical or scientific formulas, so how to derive them is key. Yet schools struggle just to get students to acquire the simple mechanics and end-products of math and science. Increasingly most high schools, perhaps due to preconceived notions, do not emphasize or even cover derivations, acting as if the formulas were brought down on two stone tablets by Moses.

As a result, you can argue that the crux of math and science are not really taught to those who don’t continue to specialise in math and science. Could it be partly why in the United States, evolution is not understood and why there is a large fraction of climate change deniers in the population? Many other countries’ educational systems are not that far behind in misguiding their youth.

In the same vein,  due to oversimplified models of matter we carry around a bricks-and-mortar-simplification in our heads every day. When some say, “we are nothing but an assembly of molecules”, they don’t realise how much they are shortchanging our understanding of chemistry, physics and biology.

Even if we don’t buy arguments along the ideas of those of Philip Goff, who suspects there are aspects of matter itself that play a key role determining the nature of consciousness, there is simply the fact that atoms and molecules are not solid lego blocks. On the contrary they are something quite special, and the sophisticated models we have arrived at , are just that, models. We have no conclusive, final understanding of what they are.

More precisely, the atom’s constituents: protons, neutrons and electrons are not like anything we experience at the macroscopic level. Sometimes they behave like particles, but in other experiments they also show wave-like properties. (Light also has a dual nature, but it’s distinct from particles because light has no mass.) When atoms bond into molecules, the energy levels of electrons change significantly. And the relationship between molecules and their energetic environment is a very dynamic one, leading to an assortment of effects, ranging from colour, synthesis and decomposition.

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Several storms of Jupiter caught by NASA’s Juno

And things get far more complicated when molecules are part of a living entity. It’s even far more complex than having to account for the weather of both Earth and Jupiter. If the reference seems outlandish, here’s what I mean. On Earth, storms are caused by the uneven solar heating of our surface and the ensuing pressure differences. On Jupiter, storms result from the uneven heating from within the Jovian planet. In living systems, molecules not only respond to external energy and to molecules from outside of cells, they respond  to the energy provided from ingested molecules and to the information provided by genetic material. The latter is not static itself–its molecules are also subject to the environment.

And it continues. At every level that molecules enter, new realities emerge. There are beautiful mutual relationships that occur between organisms: trees and orchids whose roots need ectomycorrhizal fungi to absorb adequate ions; microbiota in our gut that increase our ability to harvest otherwise inaccessible nutrients; parents who cling to their children from birth to adulthood to nourish them with molecules, habits, morals, skills and knowledge.

Isn’t it then an intellectual crime to proclaim “we are nothing but an assembly of molecules” ? The concepts of math and science are too intricate for parents to handle by themselves. But schools, books and the internet have to do a better job. Simple advertising, mere use of formulas or articulation of technical vocabulary alone will leave children’s minds unnourished.

N.B. And in case you were curious about the origin of eπi + 1 =0, here it is:

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Start with the MacLaurin series for e, and use xi as its power. After simplifying the powers of i, select-terms turn out to be the MacLaurin series for cos x, and ,after factoring out i, the series for sin x. Then if we let x = π radians and evaluate the trigonometric terms, we end up with our equation.

Postcript

Certain aspects of mathematics are a form of poetry of the rational mind. Another consequence of the relationship exi = cos x + i sin x is that if we let x= π/2, we realize that ln(i) = πi/2. From that, we can realize that ii = e-π/2. Where’s the poetry? It surfaces when you put it into words. The irrational number e, raised to an irrational power, is equivalent to an imaginary number raised to the power of itself. 🙂

Pourquoi j’aime le Québec

p1120348My wife and I lived and worked in Hawaii for a year— living there on a short-term basis was enjoyable, but the decision to move back to Québec was a wise one.

Here are reasons why I find Québec endearing .

  1. Deep-rooted conflicts have been settled here rather peacefully. In the early 20th century, Québec and Ontario had become the most urbanized of Canadian provinces. But the government had not prevented industry from being exploitative. In Québec the majority of people were (and still are) French, but enterprises were owned and managed by English Canadians and by Americans. Despite the urbanization, during Premier Duplessis 18-year tenure, he did his best to keep the province agrarian, Catholic and conservatively-minded, denying his French citizens a chance to participate in commerce. Meanwhile his administration and the Catholic Church were responsible for much corruption and abuse.In 1960, a year after his death, a new government led the province into the Quiet Revolution, which ousted the Church from social, health and educational infrastructure.  Almost overnight, as echoed by Rémy in a Denys Arcand`s movie, Les Invasions barbarespeople stopped going to church. The Lesage government nationalized hydroelectric power and financed larger projects. These supplied more power to cities that grew as more people left their farms.
  1. In Québec, the crime rate is below the national average. The vast majority don`t own guns. Even though most francophones still don`t attend Sunday mass, and many just raise families in common-law arrangements, Québecers are civil, if not just plain nice to each other, and no less moral than anyone else .map
  1. Thanks to our supply of a relatively green energy source, we have the lowest carbon footprint per capita in the country. In Gaspé most of the power is supplied by wind turbines. We are also one of the few places to have a cap and trade program for greenhouse gas emissions.

  1. Racial and religious discrimination is relatively low. A few years ago, when the Parti Québecois political party tried to exploit a minority-sentiment of intolerance, voters saw through the politicians’ attempt to manipulate them , and Marois’s party was ousted from power. A 1976 language law that made French the official language initially alienated the anglophone community, but again the conflict was resolved peacefully. Some panicked and left the province. But the English who remained made more of an effort to learn French, and in cities at least, francophones reciprocated.
  1. Our citizens are heavily taxed, but taxes fund Medicare, good social programs and an excellent CEGEP system. Many of our southern neighbours don`t understand social democracy; it only takes plain common sense to tell John Steinbeck apart from Joseph Stalin. University tuition rates, thanks to the federal government`s transfer payments, are also among the lowest on the continent. Although the bureaucracy in both health and education is excessive and large city-hospitals are crowded,  these problems could easily be fixed by replacing most administrative retirees with more good doctors, nurses and quality-teachers.
  1. Its physical geography is beautiful. Many of our city folks don`t realize it. Instead of travelling abroad, we could vacation more often within our own province. It would lower our carbon footprint and stimulate the provincial economy outside urban centres.  I will let my pictures speak for themselves.