Through The Sandglass

Summertime: the palette of beaches

Look closely, and even Hawaii's famed black sand beaches, while stark and dramatic, display their own spectrum of hues. But the diversity of origins and composition of beaches around the world leads to a more overtly dazzling palette. I recently came across, via Andrew Alden's  http://geology.about.com/, a post by travel writer Barbara Weibel that captures the spectrum of the world's beaches with some stunning photos. So, go to  http://beaches.uptake.com/blog/rainbow-beaches-colored-sand.html and enjoy.

Thinking like a pile of sand

It sometimes seems to me that managing my thoughts (and memories) resembles trying to control a pile of sand grains as they sift through my fingers. Now, new neuroscience research suggests that the analogy is not far off the mark. As reported recently in the New Scientist, it appears that the way in which our brain's neurons connect to each other and communicate is very much like the way a pile of sand behaves, and it is this that bestows on our brain some of its "remarkable powers."

Ten years ago, a Danish physicist, Per Bak, published How Nature Works: The Science of Self-Organized Criticality, a book that I devoured and still refer to (the paperback cover has an image of sand ripples; it's now, sadly, out of print and used editions seem to be going for either $130 or £130!). Bak used sand pile avalanches as an illustration of the ubiquity of scaling  or power laws in nature: the frequency (or its logarithm) of occurrence of something is proportional to a measure (often size) of that something multiplied by itself a specific number of times (raised to a certain power, mathematically speaking). Newton’s law of gravity is a power law; the pull of gravity on an object decreases with distance to the object squared. Since it decreases, Newton’s law is an inverse power law—and so is that of sand avalanches: the bigger the event, the more rare it is. But what about the “real world”? Scaling laws show up everywhere—in earthquake magnitudes (each successively larger magnitude on the scale is a multiple of the previous), population distributions, city sizes, the brightness of the Sun, and music (the structure of rock music, classical music, and the spoken word all obey scaling laws). Systems displaying this behaviour exist on the boundary between stability and instability, order and chaos, and Bak coined the term self-organized criticality (SOC)to describe this condition. It would now seem that the brain operates in this apparently precarious realm, but generally manages it rather well - and powerfully.

SOC is definitely not characterised by randomness, and, thankfully, neither are our brains (contrary to occasional appearances). If the connections between the neurons in the brain were random and structureless, then the organ would be instantly overwhelmed by the sheer numbers of useless but energy-sapping events. Nor are the neuronal connections simple - the new work makes the comparison with "small-world" networks, more flexible and powerful than simple networks, but perfectly manageable compared to randomness.

Such a network of connections allows powerful "avalanches" of neuron communication across relevant regions of the brain, often with synchronised "phase-locking" of large groups of neurons firing at the same frequency; these groups operate effectively but independently of other groups. These episodes of phase-locking alternate with periods of much greater disorder, "blizzards" of activity in which significant reorganisation seems to take place. The durations of these phases and the avalanches of firing neurons at different frequencies all seem to fit with the characteristics of SOC, apparently providing the brain with its amazing capacity to process information and with its adaptability. And also a great new excuse - "sorry, that part of my brain's phase-locked right now."

It's worth noting that power laws and SOC are compelling phenomena, but often easier to hypothesise than conclusively demonstrate. Phillip Ball has an excellent discussion of the phenomena and the problem in his new book Flow, one of his new trilogy on nature's patterns (plus lots of other good stuff about granular materials).

This fascinating topic has also been discussed on the Neuronarrative blog which includes a link to a piece on which I can't possibly comment, Why a Woman's Brain is Like an Avalanche, a Landslide, an Earthquake, or a Hurricane.

Oh, and there's also real "brain sand" - small quantities of grit often found in the pineal gland, composed of various calcium minerals, referred to as corpora arenacea, and believed by some swamis to carry holographic rhythms of the body's spatial and temporal existence.

      

A different "beginning" - and a short, off-piste, rant

Sir Laurence Dudley Stamp (my previous post) must be turning in his grave. It's ironic that, shortly after my modest proposal on the inspirational potential of a book for young scientists, I came across a different kind of inspiration - and this book, sadly, is definitely in print. You would think that a browse of Amazon's list of bestsellers in the category Professional Sciences - Earth Science - Geology might be the place to discover some gems of geo-writing, suitable for inspiring young minds. And, even allowing for the mysteries and opacity of Amazon's ranking system, it is. But, high up there in the company of John McPhee, Steve Gould, Richard Fortey, and Simon Winchester is, incredibly, the book illustrated above, In the Beginning: Compelling Evidence for Creation and the Flood, now in its eighth glorious edition. Walt Brown, Ph.D (in mechanical engineering) is the father of "hydroplate theory" - a lunatic explanation for everything, the main proposal being that monumental volumes of water erupted out of "the mid-ocean ridge" to form the earth as we know it today. And this happened - you've guessed - 6,000 years ago. Here's a graphic illustration of this event:

 

 New evidence shows that the earth has experienced a devastating, worldwide flood, whose waters violently burst forth from under the earth’s crust. Standard “textbook” explanations for many of earth’s major features are scientifically flawed. We can now explain, using well-understood phenomena, how this cataclysmic event rapidly formed so many features. These and other mysteries, listed below and briefly described in the next 11 pages, are best explained by an earthshaking event, far more catastrophic than almost anyone has imagined......

And here's the introduction to one chapter:

The Origin of Ocean Trenches and the Ring of Fire

SUMMARY: Deep folds, up to thousands of miles long and several miles deep, lie on the floor of the western Pacific Ocean, in an area centered directly opposite the center of the Atlantic Ocean. The plate tectonic theory claims that plates drifting on the earth’s surface dive into the earth and drag down the folds. Fifteen reasons will be given that show why this idea cannot be correct.

Now this is unfortunate, since supporters, wanting to have their cake and eat it , have latched on to recent reports in the scientific literature that de-watering of subducted material leads to large volumes of hydrated mantle to interpret this as evidence of subterranean oceans and thus proving hydroplate theory; they are clearly unaware of what hydrated minerals are - there is, after all, a lot of water in gypsum, but gypsum sure as hell (oops) is not water. 

There are, of course, many well-considered detailed refutations on the web of hydroplate theory - let's face it, it's not tough. I will simply leave this by saying that I have no objection to anyone self-publishing complete rubbish, but this stuff should never be listed under "science" of any kind unless it's a subcategory titled "fantasy." I'll leave you, without comment, with the words of one "editorial review" of this fine book, and I promise to return calmly to my usual theme in the next post.

The single most useful resource I know of on origins, bar none .... If I had to send my child off with only two books, they would be the Bible and In the Beginning. (Dr. Kent Davey, Senior Research Scientist, The Center for Electromechanics, University of Texas).

[p.s., the subtitle of this post derives from my wife's habit of going on a random walk in a supermarket - she describes herself as going "off-piste" and her husband as becoming "piste-off"]

Inspiration - the beginnings of a geologist

 

The question asked for this month's Accretionary Wedge collection resonated immediately with me. A while ago I wrote a short piece for Geoscientist, the magazine of the Geological Society here in London, reflecting on my own beginnings and seeking ideas on ways in which potential young geologists of today might be inspired. And recently I have been thinking about reworking the piece for Through the Sandglass, so this month's blogfest has prompted me into action.

What was the origin of our enthusiasm, what inspired our curiosity – what “turned us on”? These are probably not questions that we often ask ourselves, and it was only in some moments of retrospection during the writing of my book that any real focus came into my mind. I was in some ways lucky - after the usual young male aspirations of fighter pilot and then architect, I settled on geology early on; but then I thought that my luck had run out, for I was informed that to be a geologist required skills in physics, chemistry, and maths - at the time my three worst subjects at school. Then I got lucky again .... but I'm jumping the gun here.

My early interest was aroused through family holidays, particularly in the southwest of England – Cheddar Gorge (our Grand Canyon in a kid's eyes), the beach at Charmouth (now part of the Jurassic Coast World Heritage site), recently flood-devastated Lynmouth and the thrill of the venerable but valiant family car attempting the daunting gradient of Porlock Hill (my father all the while declaring that “it’s better to travel hopefully than arrive”). Such adventures offered treasured opportunities for satisfying a child’s love of finding things and (prevailing on indulgent parents) collecting stuff. And boy did I collect stuff - my father always enjoyed recounting how a heavy box, shipped back from holiday, was lugged to our front door by the mailman (or postman) who asked, indignantly, "Wot you got in 'ere, then, rocks?" The affirmative reply was greeted with a look that clearly defined us as demented. And then, perhaps in the hope of imposing some focus and coherence on my collecting activities, I acquired some geology books. British readers will remember the Observers series, pocket-sized answers to everything that could be observed and the one on geology became a treasure. There were others - one titled Pebbles on the Beach, which I thought was fascinating (I appreciate now that it was a sort of introduction to sediment provenance) but seems to have sunk without trace; another was by H.H. Swinnerton, Professor of Geology at the university in the town where I was born and began growing up, Nottingham. Swinnerton's book was Solving Earth's Mysteries, or, Geology for Girls and Boys, and the pictures were fantastic - I still get strange flashbacks flipping through it today.

But there was one book in particular that I now appreciate was the book, the one that was truly inspirational and turned me on to geology, and my copy, “slightly foxed” through my devoted attentions, has now regained its place on my bookshelves. The book was by L. Dudley Stamp (Sir Laurence as he was to become), an economic geographer at the London School of Economics, who strode the fertile lands between geography and geology for much of the twentieth century. Among his many achievements, he commandeered schoolchildren and vicars across the country to compile the first comprehensive land use survey of the country, which allowed crucial agricultural and urban planning during the Second World War that otherwise would not have been possible.

Probably the best-known of Stamp's books is Britain’s Structure and Scenery, but for me the true treasure, the book which I now appreciate fired my fascination with geology, was The Earth’s Crust—A New Approach to Physical Geography and Geology. Published in 1951, it was called “a new approach” because Stamp commissioned huge, detailed models of different landscapes—and what lies beneath them—to be made in exquisite detail by Tom Bayley, a lecturer in sculpture, and photographed in colour for the book.

For me, this was magic. I was captivated by the illustrations, several of which I've reproduced here. I scrutinised the models in detail and even tried, messily, to make some myself. They opened my eyes to how landscapes and their foundations worked, I could look around me on those summer holidays with a different understanding—I could visualise things. And, best of all, some of the models depicted change: for example, the appearance of a glaciated valley when it was still filled with ice and after it had melted (good for Welsh or Scottish holidays!). My curiosity about the world around me was aroused. I was alerted to geology.

The book is, sadly, long out of print and difficult to find, but for me, to open it up today is a deeply evocative and sentimental experience.

After my piece came out in the Geoscientist, the theme was continued by Jon Noad, who began with the following:

Michael Welland recently described how a treasured geological book "fired his fascination" with geology. I too had such a book (The Age of Reptiles by Zallinger), but of even greater significance were those people who fostered my love of geology.

And, of course, he's right - people are potentially more important than any book in firing up young minds. But to find the right people is arguably a matter of good fortune - which is where my getting lucky again comes in. My battle for comprehension, never mind mastery, of maths and the sciences, would have been inevitably lost had it not been for one teacher in high school - he performed miracles. And yes, there were many other people who were key to my evolution into a geologist. But I guess that my point is that every kid deserves that lucky break where the right person shows up in his or her life to inspire them - but until that happens, there are other things that can be done if we learn from our own experiences - and books like The Earth's Crust have an intangible, academically unconventional, something that we might learn from.

Streams of grains - some more amazing granular research

As I'm sure I've said before, to watch the sands of an hourglass in action is to observe all kinds of natural phenomena at work - and all kinds of questions to which we have no answers. It's not just the cascades and avalanches, but the liquid stream of grains itself that holds mysteries, interactions and behaviours too minute and too rapid for the eye and the brain to grasp. Traditionally, we have to resort to statistics, to averages, to clumps and groupings - to model at the level of individual grains is just too complex and there are too many of them. But now we are beginning to be able to peer into the nano-world of an individual grain and to simulate its interactions with its colleagues, thanks to the continuing, revelatory, research into granular materials. Friends have recently drawn my attention to two specific examples that I'll mention here.

The University of Chicago has long been a fluidised bed of granular behaviour research, with Sidney R. Nagel and Heinrich M. Jaeger as the uber-gurus of the bizarre (remember the Brazil nut effect and then the reverse Brazil nut effect), and now Jaeger, together with his students and colleagues, has yet again achieved something extraordinary. Look again at the flowing stream of sand grains in the hourglass: until recently, studies of so-called "free falling granular streams" tracked shape changes in flows of dry materials, but were unable to observe the full evolution of the forming droplets or the clustering mechanisms involved. But, as recently reported in Science Daily, with the aid of a very expensive and very high-speed camera, Jaeger has been able to track the formation of "droplets" in the granular stream and show that surface tension effects 100,000 times smaller than those that operate in liquids are at work. The dry material behaves as if it were a liquid with very low surface tension - as suggested in the graphic at right, above, and a short but dramatic video is available at the NSF site here.

"At first we thought grain-grain interactions would be far too weak to influence the granular stream," said John Royer, a graduate student on the team. "The atomic force microscopy surprised us by demonstrating that small changes in these interactions could have a large impact on the break up of the stream, conclusively showing that these interactions were actually controlling the droplet formation." So streaming sand not only looks like a liquid, but actually behaves like one, once again raising the question of exactly what form of matter this is. And, as with all this kind of research, it's not just of academic interest - the efficient filling of pharmaceutical capsules is but one (important) industrial process that could benefit. And it's also a further wonderful example of the deeper we look, the more complex things become and the more the questions that are raised. As Jaeger says, these "experimental results open up new territory for which there currently is no theoretical framework."

So Jaeger is breaking new ground in the experimental observation of individual grain interactions, but are we doomed to be unable to computationally model these things, overwhelmed by the sheer numbers, the scale of the problem in a different sense? Well, no, not if Dan Negrut, Toby Heyn, and Justin Madsen at the University of Wisconsin have anything to do with it. Working at the Simulation-Based Engineering Laboratory in Madison, they have developed both the theoretical and mathematical basis, and the power of parallel computing, for modelling the movements of huge numbers of grains. There's a report on their work on Science News, but the best thing to do is to go to their website and enjoy some of their simulations (you'll need to download the VLC viewer for which instructions are given). Not surprisingly, my favourite is their virtual hourglass (illustrated at left at the top of this post); this uses the relatively modest number of 25,000 individual "objects", i.e., grains, but it's incredibly realistic. There are other simulations involving hundreds of thousands of grains and the capability is growing all the time - Negrut hopes his simulation will analyze millions of grains in a single day, if not a matter of hours. To model the interactions of individual grains requires a firm theoretical foundation and the team has made great progress in establishing this; a planned collaboration with Professor Alessandro Tasora from the University of Parma will further refine this. Negrut kindly supplied me with a preprint of the group's forthcoming paper, A Parallel Algorithm for Solving Complex Multibody Problems with Stream Processors. Unfortunately, I have to confess that it's entirely beyond me, even the abstract outstripping my modest mathematical and computational capacity. Here's an extract - I recognised two sand grains in Figure 1 and was then terminally lost:

 

But among the simulations viewable on their website is one of work they are doing on a Mars rover moving over granular materials. This, as I recently noted (Stuck in the Sand) is currently a major problem for the Mars Rover Spirit, and its engineers back on earth. Thanks to being again alerted by a reader, I now find that the Rover's dilemma (sounds like the name of a pub) is being used to good effect to study details of the diverse granular materials revealed by its spinning wheel. As reported in Science Daily, "One of the rover's wheels tore into the site, exposing colored sandy materials and a miniature cliff of cemented sands. Some disturbed material cascaded down, evidence of the looseness that will be a challenge for getting Spirit out. But at the edge of the disturbed patch, the soil is cohesive enough to hold its shape as a steep cross-section." Ray Arvidson of Washington University in St. Louis, deputy principal investigator for the science payloads on Spirit and its twin rover, Opportunity, said "We are able here to study each layer, each different color of the interesting soils exposed by the wheels," adding that "The layers have basaltic sand, sulfate-rich sand and areas with the addition of silica-rich materials, possibly sorted by wind and cemented by the action of thin films of water. We're still at a stage of multiple working hypotheses." Below is an image of the revealed materials (NASA/JPL-Caltech/Cornell University).

 

There is, literally, no end to the extraordinary journeys that granular materials can take us on, so next time you watch an hourglass in action, think of low surface tension liquids, parallel computing and Spirit.

[I have to thank Richard Cathcart and Dominion Rognstad for drawing my attention to these topics - my theme for this blog is so wide-ranging that I can't possibly keep track of all the items of interest and I very much appreciate any suggestions and links that readers might send me.]