Through The Sandglass

It's all about size: Martian dust devils

 

I use this image as my desktop, so each day I gaze at it in wonder. It’s natural art and design, somehow mysterious, somehow sensual. This extraordinary – and much-publicised – image is from Mars, captured by the high resolution orbiter, and reveals the tracks of dust devils, whirling miniature tornado dervishes of wind engraving their way over the dunes. But exactly how these dark tracks form has been something of a mystery: is it to do with composition, that light dust is removed to reveal sand of darker materials beneath?

Ironically, more observations had been made of this phenomenon on Mars than on Earth – orbiters and rovers have gathered a gallery of images and movies of dust devils on the Red Planet:

 

Earlier this year, Dennis Reiss, a geographer at Westfälische Wilhelms Universität Münster in Germany, together with his colleagues, reported on their earth-bound fieldwork in the Turpan Desert of northwestern China. Dust devil tracks are small and ephemeral things here, whereas the Martian designs are larger and last far longer. But the workers in China were able to observe dust devils at work and examine the character of the dark trails left behind. What they showed was that the appearance of the tracks was dependent on the size of the grains. The sand grains outside the tracks were coated with fine dust that brightly reflects the light. Within the tracks the blast of the passing dust devil blew the sand along, tumbling and saltating, with the result that the dust was picked up by the vortex and clean sand grains were left behind. Smaller grains appear lighter than coarse ones – they reflect more light and their albedo is higher – and so the tracks appear darker than the surrounding sand.

So far, so good. But there are examples, as recently reported by Mary Pendleton Hoffer and Ronald Greeley at Arizona State University, of dust devil tracks on Mars that are lighter than their surroundings:

 

Reiss and his colleagues have now reported on light-coloured tracks from the Turpan Desert. These appeared in sand that had been darkened by a brief rain shower the previous night. But invoking rain on Mars is clearly a non-starter, so what is going on? Well, it turned out that the sand within the light tracks was no different from usual – millimetre-sized grains cleansed of finer material. But, the darkening of the surrounding sands was a result of the grains being cemented together by the rain into clumps up to a centimetre across. Big clumps = low albedo = dark appearance. The dust devil had broken these up, brightening the sand left behind in its track.  

OK, but there’s still no rain on Mars. However, there are forces that can clump sand grains together – electrostatic forces. Such clumping has been observed by the field geologists on Mars, the indomitable rovers.

In 1979, Greeley conducted lab experiments showing that charges build up on dry, wind-blown sand particles in a similar manner to the way charge builds up on a balloon when you rub it on your hair. Just like the charged-up balloon can stick to the wall, charged sand grains pull together to form delicate, “popcorn ball” aggregates.

“The destruction of aggregates on Mars would lead also to bright dust devil tracks,” Reiss said.

Greeley thinks the idea makes sense. “This is a plausible model for the formation of the bright tracks on Mars,” he said. “This is a very nice study, a very nice result.”

So, through questions raised on Mars we are better understanding processes on our own planet. The wonder of Martian calligraphy is, however, by no means diminished.

 

[See the amazing gallery of Mars high resolution images at the HiRISE site. Images courtesy of NASA/JPL/University of Arizona HiRISE]

  

Sunday sands: Utah, Omaha, Gold

 

I’m in France, so this provides a theme. I’ll start with France’s most famous – and infamous – beaches: Normandy. I visited that stretch of coast for the first time almost exactly a year ago; I found myself carried along in an ever-changing and unpredictable series of emotional responses, sobering, awe-inspiring, depressing, fascinating, and mystifying.

It is said that the sands of the Normandy beaches reflect, like those of beaches around the world, local ingredients: they contain grains of steel.

I think that no further narrative is required.

 

Important geological experiences: an innocent abroad

The year was – dear me – 1968. I had finished my undergraduate degree at Cambridge (England) and was preparing for a summer’s fieldwork in the Arctic. But I had made a couple of decisions: I needed to get out of Cambridge and I felt that there remained important gaps in my education. In the British system you would finish undergraduate work and, if you wished to continue, embark immediately on PhD research – for which I did not feel fully equipped. I found the American approach of graduate coursework prior to the research phase immensely attractive, a means of filling in some of those gaps. And postgraduate work at an American university would offer fresh fields and pastures new. I was lucky – I had been accepted at Harvard and so, having reassembled myself after a few months camping in Spitsbergen, I decamped to Cambridge (US).

The array of course offerings was inspiring, but two were, as they say, “no brainers.” One was the opportunity to fill the gap of the business of geology, an arena clearly beneath the dignity of the ivory towers of Cambridge (UK) – a course in mining geology that proved fascinating. But it’s the other that comes to mind in the category of “important geological experiences.” A graduate seminar course in geosynclines, taught by Bernie Kummel and Ray Siever; these were names that I knew well from their textbooks and research, Kummel in stratigraphy and palaeontology, Siever in sedimentology (together with Francis Pettijohn and Paul Potter, he was responsible for the all-time classic and never-leave home-without-it book, Sand and Sandstone).

But we’re talking ancient intellectual history now - “geosyncline” is today an obsolete term, but in the 1960s it was simply in its latest incarnation after decades of representing the explanatory model for mountain belts. The great thicknesses of deformed sediment contained within any mountain belt must, according to geosynclinal theory, represent accumulation in great troughs in the earth’s crust that would later be uplifted. The fact that recognising any geosyncline existing anywhere on earth in the 1960s was a challenge was not a deterrent – there was, after all, apparently no alternative explanation for the great mountain chains of the world. Except, of course, that by the time I arrived in Cambridge (US), there was.

For the previous three years in Cambridge (UK), I had been raised in the heady atmosphere of the birth of plate tectonics; the atmosphere and the individuals involved were extraordinary – I have written about this before; as an undergraduate of course I had learned about geosynclines and their multiple subcategories christened with a glorious selection of Greek prefixes – eugeosynclines, taphrogeosynclines, zeugogeosynclines… But the excitement was the mechanism that would replace them. I was steeped in the emerging power of plate tectonic theory to explain and integrate, to set out convincingly the origin of orogens, mountain belts.

So, when I signed up for the seminar course at Harvard, my assumption was that we would be examining the character of geosynclines and transferring this knowledge into the context of plate tectonics. As the foreign representative on the course, I was nominated to give the first presentation – an intimidating prospect. As the trans-Atlantic representative, I was given the topic of the Caledonides, the long chain of ancient mountains that stretch from the Arctic to the Ouachitas, via Norway, Scotland, Wales, Ireland, and the Appalachians. All the segments clearly belonged to the same geological family, sharing, with genetic variations, timing and character. But using the 1965 Bullard, Everett, and Smith Atlantic reconstruction, they could clearly be seen as no longer segments but a unified whole resulting from a complex sequence of plate collisions – a joined-up story, so to speak. For my presentation I brought out several plate reconstruction graphics that I had hauled across the Atlantic; I put these up on the wall of the seminar room, and launched into the story – the Cambridge (UK) edition, that is. And then it happened. The imposing voice of Bernie Kummel interrupted my narration – and he was coming down on me like a proverbial ton of bricks. A sense of shock and horror came over me: Bernie Kummel, the Bernie Kummel, didn’t believe a word I was saying.

Nothing in my sheltered three years at Cambridge (UK) had prepared me for this. I was the innocent abroad, naively believing that the sheer elegance of plate tectonics, the compelling way in which it offered explanations for the previously inexplicable, was universally regarded as indisputable. This was my important geological experience: schools of thought come in many different forms, each with its own rationale, each with supporting evidence, each with its own fervency. I needed to not simply set out my own school of thought, but think it through, marshal the evidence, anticipate and analyse apparently contradictory evidence. This was not an argument among undergraduates at a coffee break, this was a division of views among leading scientists, for all of whom I had immense respect.  

I was fortunate that Ray Siever, who clearly was inclined towards my side of the story, came to my rescue, good-humouredly defusing the controversy and moving all towards a thoughtful discussion of the issue. And, of course, through listening to the voices of Kummel and Siever, voices of such a wealth of experience informed by seeing more geology than I had even read about, what I learned was, literally, invaluable. 

Today, I can’t help but wonder how the debate over plate tectonics (around the world: as I learned – finally -  this was a global debate) would have evolved had the blogosphere existed then. Would the voices of reason and experience on both sides have been submerged by the rhetoric and zealotry of non-reason?

This, along with my field discussion with Alan Smith, was one of those key experiences that has stuck with me and informed my way of thinking ever since – and I will be eternally grateful to Bernie Kummel for providing it.

[This story is a response to the latest Accretionary Wedge theme]

A climate science recommendation, the Pakistan floods, and, of course, sand

 

The “science” component of “climate science” has seemed for some time to have been largely eclipsed by rhetoric, sound-bites, grinding axes, and the shrill voices of the blogosphere. Attempts at lowering the emotional level of the “debate” semantically - “global climate disruption” instead of global warming, climate “cynics” (avoiding the unpalatable connotations of “deniers”) – make little difference; the very human nature of cognitive biases will always win out. Although it is not my intent, for the moment at least, to enter the fray of post-climategate and post IPCC review turbulence, I would suggest that one thing is clear: the loss of trust in not only climate science but science as a whole is both tragic and potentially hugely damaging.

In this sad state of affairs, it seems to be a fact of life that, in order to find primary sources and reliable voices of reason, a complex and often highly irritating navigation of the blogosphere is necessary – much of the discussion (again, often a euphemism) takes place there, and much of it is vituperative, tribal, and composed of anonymous ad hominem commentary. It has therefore been with some pleasure that I have recently been following a new climate science blog, Climate etc., the initial welcome and purpose for which can be found here. To quote:

 This blog provides a forum for the exchange of ideas about climate science and the science-policy interface.  Climate Etc. is envisioned as a gathering place for climate researchers, academics and technical experts from other fields, citizen scientists, and the interested public. Open minds and critical thinking are required, and stimulating discussion and group learning is expected…The climate blogosphere is a vibrant environment but the signal is often hidden by the noise.  Towards separating the signal from the noise, Climate Etc. will experiment with different formats…The idea is to have a focused and snark-free environment in which academics and other technical experts with little or no blogging experience will feel comfortable engaging with the broader community.

The blog has been set up by Judith Curry, who is a hurricane science and atmospheric modelling specialist and has been the Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology since 2002. I met Judith at the Scifoo event a couple of months ago; I talked to her initially because the sandfish robotics work that had fascinated me was done at Georgia Tech but our conversations moved on to the issues faced by climate science and how to better deal with describing uncertainty (Judith kindly joined me in facilitating a discussion of this at the event). Despite her reputation as an academic scientist, she had recently been tarred and feathered in certain corners of the blogosphere for simply recommending that scientists should read Andrew Montford’s book, The Hockey Stick Illusion (see, for example, this review). I have now read it, and found it as compelling as a well-written detective story – I recommend it, but the details are for another time. Judith has started Climate etc. with the aspiration of providing a rational place for discussion of climate science issues, free, as far as possible, of “noise.” In my view, she has succeeded: her own posts are interesting, balanced, and provocative in the right way, and the commentary is largely free of rhetoric, filled with useful links, and, astonishingly, largely written by people who use their real names.

But I’m writing here about Judith’s blog not simply because I wanted to recommend it, but to follow up on her post from a few days ago, Pakistan on my mind. In it, she describes the fact that, in the aftermath of the devastating floods, “Most of the response of the climate research community to this catastrophe has focused on the attribution of the floods, i.e. whether greenhouse warming played any role in causing the floods,” citing, for example, Christiana Figueres, head of the U.N.’s Framework Convention on Climate Change, who stated that “All these events are constant reminders to governments that they need to deal in a consummate manner together to address climate change.” Judith asks two compelling questions: with what confidence can we ascribe these events to climate change and, regardless, is this the right approach to attempting to understand, manage, and ameliorate the impact of these events? The post and the (extensive) comments are informative and well worth reading. But I was particularly interested in the following section:

...the Climate Himalaya Initiative argues that engineering structures and human error may have played a major role in the catastrophe. There are a substantial number of barrages (dams) on the Indus River that support irrigation and hydropower.  The flood occurred when the rising river bed (owing to the huge silt deposition in the upstream areas) was trapped by the Taunsa barrage, obstructing the water flow. These heavy silt loads were then transported through western tributaries of the Indus River. Construction of protective levees and dykes has also contributed to raising the riverbed and the sedimentation of upstream areas; moreover, the rising riverbed levels have rendered protective levees ineffective.

So, I thought that I would follow up a little (and my apologies – this follow-up has evolved into something that is certainly not “little”). The Indus system is huge, fascinating, and complex. A few facts:

1. The Indus itself is over 3000 kilometres long, rises on the Tibetan Plateau, and drains an area of more than a million square kilometres (see the map and satellite image at the head of the post – and note the areas marked “modified landscape”).
2. The vast network of tributaries flow into the Indus from Afghanistan, China, and India as well as from within Pakistan. The south-eastern tributaries are controlled by India, under the terms of the Indus Waters Treaty of 1960.
3. The Indus is, by nature, one the largest sediment-producing rivers in the world, transporting debris from a huge area of the Himalayas where erosion rates can be up to 4 mm per year.
4. The sediment load of the river (the suspended stuff – see my discussion of what we don’t know about bed load) varies enormously during the course of a year – during the monsoon and the summer snow melt the river will carry up to a thousand times as much sediment as it does at its low point.
5. There are ten major dams and countless smaller dams and barrages along the Indus and its tributaries: it has been effectively engineered into the largest integrated irrigation system in the world.

As it emerges from the Himalayas, the Indus itself carries around 300 million tons of suspended sediment per year – let’s say around 15 million good-sized-dump-trucks-full. Prior to 1947, much of this sediment settled on the plains, but still a substantial volume reached the delta which was typically growing out into the ocean at a rate of 30 metres per year. But today, as it emerges from the mountains, the river reaches the huge reservoir of the Tarbela dam:

 

Downstream of the dam, the suspended sediment load is a mere 2 million dump trucks per year, the rest trapped behind the dam. Well, not right behind the dam, but rather dumped in the reservoir. When the dam was completed, in 1976, the estimate was that it would have a lifespan lasting only until 2030, by which time the reservoir would be completely filled with sediment. This proved to be pessimistic, but the fact is that 6 billion tons of sand, silt and mud had accumulated in the reservoir in the first twenty-five years of the project’s life. And all that sediment is building up in a huge delta below the surface of the water, slowly growing downstream towards the dam; not only would an earthquake potential set off a devastating underwater landslide, threatening the dam, but, even without such an event, the delta is fast approaching the intakes and tunnels of the dam. So, what can be done about this?

Well, unfortunately, the answer requires a slight diversion into the arcane but vital concept of a river’s base level. I made an attempt to describe the concept in the book:

Take a map of a river and run a piece of string along its winding course; then straighten out the string and draw a graph of the river’s elevation versus the distance from its source—the profile of the river. For any river at any given time, there are two points that are externally fixed: sea level and the elevation of the source of the river in the mountains. Between these two points, the river is free to behave in any number of ways. For the river, sea level is the primary base level, its ultimate terminus, below which no part of the river can drop (to avoid the impossible feat of flowing uphill). Base level is a concept universally agreed on and at the same time hotly debated, but the principle is clear: change a river’s base level by raising or dropping sea level, and the river must change its behaviour. If base level drops, the river must erode, cutting downward to reflect this. If base level rises, the river must build up its profile by depositing sediment. A change in base level changes the gradient of the river’s profile, requiring the river to make changes in order to smooth out that profile.

So sea level is the primary base level and sea level changes profoundly alter a river’s behaviour and architecture. But put a dam in the middle of a river and you have introduced an entirely new local base level, and, upstream of that dam, the river responds. You have raised the base level from the natural altitude of the river’s valley before the dam and therefore the river reacts by depositing its sediment load. If the level of the reservoir is maintained as constant then the system reaches a new stable state, but if the level varies, then the river continues to respond by erosion or deposition. In the case of the Tarbela delta problem, the reservoir level has been raised to induce more sediment to be deposited upstream, therefore depriving the delta of sustenance. But that upstream deposition continues to completely modify the geometry of the valley (that had anyway not been natural since the dam’s construction) – and the environment on which depends the livelihood of everyone who lives there. The floods upstream of the Tarbela dam were appalling.

So this is but a vivid example of how the entire Indus system has been modified. It is modified every time a dam is built and it is modified every time the level of water in a reservoir is changed. It is a totally and dynamically unnatural system, deprived of sediment and, today, virtually no sediment at all reaches the delta of the Indus. Floods on the scale of those recently experienced would always have been devastating, but their impact is exacerbated by the wholesale manmade modification of an entire river system.

In her conclusion, “Looking forward,” Judith Curry writes:

While climate researchers and policy makers ponder whether the flood can be attributed to global warming, it seems to us that this emphasis diverts attention from actually using climate, meteorological and hydrological knowledge and research in the application of pressing current needs in the developing world.  Substantial benefits would accrue directly for developing countries, as well as indirectly for other countries concerned with global security, by applying advanced research and technologies to support:

• improved river routing models for major rivers
• advanced techniques for providing probabilistic flood forecasts on timescales exceeding two days and integration of these forecasts into early warning systems, preparedness and contingency plans, and rehabilitation measures
• application of advanced dynamical and statistical methods to assess future risk of floods and droughts, and integrate this information into engineering assessments for future water structures
• improved probabilistic rainfall forecasts on timescales of days to weeks to enable farmers to optimize agricultural decision making regarding planting and harvesting.

Based upon our work in Bangladesh along these lines (see here and here),  we have demonstrated that such developments are feasible and can be successfully integrated into national meteorological and hydrological services.  We have contacted the Pakistan Meteorological Department and have had discussions with relevant personnel in USAID and UNDP regarding how we might help.  The current situation in Pakistan is mired in both national and international politics. However, we hope that the international climate, meteorological and hydrological communities can offer something to help Pakistan other than a debate over whether global warming contributed to the floods and a mistake in the IPCC AR4 regarding the melting of the Himalayan glaciers.

Other than possibly adding a few more geological – and specifically sedimentological – components to her list, I agree wholeheartedly and can only wish her and her colleagues every success.

……………………………………………………………………………………………………………………………………………………………………………………………….

For a further sense of the complexity of the Indus basin and the distribution of dams and barrages, plus data on catchment flows in July and August this year, here’s a map from the World Food Programme – the high resolution version can be found here.

 

[For an overview of the role of dams in the Indus basin, see this paper from the International Commission on Large Dams. For details on sedimentation in the Tarbela dam reservoir, see http://www.adb.org/water/topics/dams/pdf/cspkmain.pdf, and http://www.paralia.fr/cmcm/e01-28.pdf; for an interesting piece of research on the sands of the Indus, see “Petrology of Indus River sands: a key to interpret erosion history of the Western Himalayan Syntaxis”; for extensive documentation of the recent landslides in the upper reaches of the Indus system as well as of the flooding, see Dave’s Landslide Blog, written by Dave Petley, who is the Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the UK.] 

Sunday sand: Old Lighthouse Beach, Cape Hatteras

 

There’s a good reason for the beach’s name – not because it has an old lighthouse on it, but because it used to and now doesn’t.

When I was writing the book, I derived great enjoyment from the travails of lighthouses around the world as symbolic of shape-shifting shorelines and dynamic sands; lighthouses overwhelmed by sand, lighthouses deprived of sand and therefore their foundations. Cape Hatteras is a great example. The sand shoals of the cape extend far offshore and have claimed many ships over the years, including, famously, the ironclad Monitor during the Civil War; this is one of the candidates for the “graveyard of the Atlantic.” The “old lighthouse,” with its distinctive black and white spiral, and its pride as the tallest in the US, was originally built, from brick, in 1868-70. But time and tide – and storms - wait for no man nor manmade structure, and, by the early twentieth-century, the lighthouse was under threat. I’ll let what I wrote for the book continue:

If you had happened to be enjoying a fine day in late June 1999 by taking a walk along the beaches of Cape Hatteras, on the Outer Banks of North Carolina, you would have thought that your mind was playing tricks. You might have dismissed it as an illusion of some sort and sat on the beach, keeping an eye on your dog and sifting sand grains through your fingers—any one of which might have been our sand grain resting on its journey southward after its escape from the Chesapeake. But the sensation of uneasiness would have remained, and you would have inevitably turned back to look again at the huge, candy-striped lighthouse—and yes, it had moved.

This would not have been a trick or an illusion, a sign of your deteriorating faculties. The Cape Hatteras lighthouse, the highest in the country at over 60 meters tall and a historic icon, was on a slow, 900-meter journey from where it had stood for 129 years to a new, safer location. When it was built in 1870, it stood 500 meters from the shore. But the same treachery of the ocean that required the lighthouse to warn ships of offshore shoals had threatened the structure itself. By 1935, the waves were crashing only 30 meters from its base. The beach had gone, carried away not just by the regular storms of the Atlantic, but also by daily wear and tear, washed away by the same processes that move the sand between your toes. The cumulative effect of those processes is that Hatteras Island in its entirety is continuously migrating westward.

To move a lighthouse is no trivial task, and many different alternative engineering solutions had been tried over the decades. Since the 1930s, huge lengths of massive steel sheets had been driven into the shoreline to form groins, walls against the sea. The groins were extended and repaired, but time after time storms found their way around them to slam into the defenceless sands and move them on again. In 1966, fourteen thousand dump truck loads of sand were pumped from neighbouring Pamlico onto the beach in front of the lighthouse, but the sand was fine, puny stuff, easily dismissed by the waves, and dismiss it they did. In 1973, in a further attempt at what, in the trade, is referred to as beach nourishment, another fifty-nine thousand loads of sand were moved from the cape to the lighthouse defenses, only to be swept away within a few years. By 1980, the sea was once again threatening the lighthouse, and sandbags, rubble, and rubber mats were dropped offshore. None had any lasting effect in the face of the stubborn aggression of the ocean. In 1988, the decision was made to retreat, to move the lighthouse, lock, stock, and lantern, inland. The structure, weighing close to 4,000 tons, was jacked up off its foundation in June 1999 and moved on tracks at around two meters per hour over a period of twenty-three days. The lighthouse now stands roughly the same distance from the sea as it did when it was first built. The waves continue their action—as they have, of course, been doing for millennia.

 

Before and during the move

I have long had a yearning to explore the Outer Banks, and, one day, most certainly will – and collect my own sand. But I was lucky enough to find that Betsy Kimak, who runs the award-winning Sandrific site, could provide me with some in the meantime to keep my imagination going. And so there it is, this Sunday’s sand, plucked rudely from its epic journey down the Atlantic coast and incarcerated in London – a frustrated sand. It’s mainly quartz grains, some quite angular, some wind-rounded, all with a history of being left behind as the debris from melting glaciers, or uprooted from the mountains of the Appalachians and flushed to the coast, down the Susquehanna, down the Hudson; for many of these grains this will simply have been the latest uprooting in a series of cycles over hundred of millions of years – who knows what stories this grain has to tell?

 

The “dalmatian” grain in the image on the right at the head of the post is a youthful character, its rough edges hardly affected at all by its journey to the Cape. This is probably a fragment of a metamorphic rock, cooked in the turmoil of the building of the Appalachians, or even from some older, distant, and glacier-scoured bedrock. Each grain unique, each grain simply a frame in an epic movie.

 

[Fore further details on the lighthouse and its extraordinary move, the Wikipedia page is a good start, plus the National Park Service site – Cape Hatteras was the first National Seashore – and the good old US Army Corps of Engineers has a nice “historical vignette.” Photos from the North Carolina Division of Highways] 

Sand baths

For one reason or another, I have been browsing some details of the historic voyage of HMS Challenger, whose global exploration in the 1870s shattered all preconceived notions of what the oceans contained and set the scene for modern oceanography. On December 21, 1872, fourteen years after Charles Darwin had published his revolutionary ideas, a small converted British naval vessel slipped out of Portsmouth, beginning a voyage that would last three and a half years and revolutionize our understanding of the oceans. HMS Challenger (after which the space shuttle was named) had been converted into a research vessel. Her guns had been replaced by laboratories and her munitions stores by over 400 kilometers of rope and wire for surveying and sampling the ocean floor. The voyage covered 130,000 kilometers and cost more than $20 million in today’s money. The incentives were many, but two stood out: the needs to plan for global communication via undersea cables and to test the longstanding belief that the deep oceans were lifeless wastes. The latter was dramatically proved wrong, and the former accomplished by large numbers of soundings that first demonstrated the topographical grandeur of the ocean floors. In waters off the Pacific Mariana Islands, a depth was recorded of 8,200 meters. What became known as the “Challenger Deep” remains the world record-holder today, its greatest known depth later measured at close to 11,000 meters. Ocean chemistry, temperatures, and huge amounts of other data were collected and, with the publication of the fifty-volume report, oceanography was born.

Among the vast array of results was the demonstration that sand, albeit in relatively modest amounts, could find its way out onto the deep ocean floors. But that’s for another day. Wonderfully, essentially the entire original documentation of the Challenger voyage is available online (details below), and, on investigating the details of the scientific equipment carried on board, and the contents of the “chemical laboratory,” illustrated above, I discovered the “sea-going sand-bath”:

  

Now, the use of sand baths as physical stabilisers and thermostatic surrounds for laboratory vessels goes back a long way, and continues today. Here are a couple of examples from modern laboratory suppliers, the one on the right even providing a fluidised bed of sand.

 

The blurb accompanying an example of a modern sand bath goes as follows - “sand as a paradox”:

Sand-bath Method:

A sand bath is good for microscale procedures only, because sand is a paradox — it's a better insulator than it is a heat transfer material. The unique thing about a sand bath is the big temperature gradient that it can generate. For example, fill a 100-mL THERMOWELL (use no other size heater) with quality sand, operate it for at least 20 minutes at the maximum 40% power (75v or 145v) and the temperature of the sand's surface is about 100°C , and the bottom of the sand bath is almost 400°C. Touch a small test tube containing 1 mL of water to the sand surface and you get gentle heating, but push the test tube down to the bottom of the sand bath and the water boils in a few seconds.

So, the wondrous performance of sand in this way also explains its widespread historical use, particularly for “delicate distillations” – in the infernal labs of the alchemists. As described by a modern practitioner, Robert Bartlett, in his history of, and practical guide to, the dark arts:

The third degree of heat is called the Balneum Arena or sand bath. It is set up like the water bath but it is able to maintain a higher heat than the water or ashes. Many oils and substances with boiling points higher than water can be heated and distilled with the sand bath. It provides and even heating of the matter and avoids hot spots from developing. In fairly high heats, the sand bath also lends support for the vessel which might otherwise become deformed from the heat.

An eighteenth-century translation, “Written for the use and employment of the Lover of the Noble Hermetic Philosophy,” of a work written six hundred years earlier describes a toxic recipe following the misguided belief that arsenic, particularly in large quantities, had beneficial medicinal properties (a belief that contributed significantly to the mortality rate among alchemists):

 Let it be purified thus: Take of the Crystalline Matter sublimed; Let it be ground upon a marble, with an equal part of Calx of Luna, and let it be put into a Vial sealed, and set in a Sand bath again, the first two hours with a gentle Fire, the second with a stronger, and the third with one yet more violent, and increased till the Sand will hiss, and our Arsenic will be sublimed again, the starry Beams being sent forth...

Do not try this at home.

In the eighteenth-century, The Universal Magazine of Knowledge and Pleasure, provided “News, Letters, Debates, Poetry, Musick, Biography, History, Geography, Voyages, Criticism, Translations, Philosophy, Mathematicks, Husbandy, Gardening, Cookery, Chemistry, Mechanicks, Trade, Navigation Architecture and Other Arts and Sciences, which may render it Instructive and Entertaining to Gentry, Merchants, Farmers, and Tradesmen.” “Chemistry” was, of course, primarily alchemy, and, in 1751, in a section titled the “Third View of Practical Chemistry,” the following detailed illustration appeared (my thanks to the BibiOdyssey blog for the source):

 

The game is “spot the sand baths.”

According to the key, there are seven:

A, a furnace for distilling in balneum mariae.
B, a furnace for making spirit of hartshorn, &c. in great quantities, e, its head, and b,b, two receivers.
C, a sand furnace; d a retort placed in it.
D, another sand-furnace, having a copper distilling body placed in it, to which it is fitted (d) a glass head, and (e) a receiver.
E, a small open furnace for divers uses, as boiling syrups, evaporating liquids, &c.
F, a wind-furnace, blown by the bellows, M, f a cucurbit in a copper vessel with sand, placed over the furnace.
G, a sand-heat, with a retort and a receiver.
H, H, two sand-heats, in each of which is placed a retort k, m, for distilling volatile spirits, one of which has a single receiver l, and a double one i, k.
I, a cold still; n and o the receiver.
K, a sand-heat, in which a retort q, having a large receiver p fitted to it for making sal volatile.
L, a digesting furnace, having a circulatory vessel r, s, placed in it for extracting tinctures, &c.
N, O, P, three chimnies, which, after uniting, join the main chimney of the laboratory.

So, sand has been an indispensable material in the laboratory for a very long time indeed – 800 years of sand baths.

But if you google the term “sand bath” you will today come up with some bizarre images. I’ll avoid referring to the most bizarre, but here’s an example:

 

The supposed therapeutic qualities of hot sand, in particular black sand, continue to be exploited around the world, but nowhere to the degree of sophistication that the Japanese coastal resort of Beppu demonstrates. Blessed with many geothermal springs, bathhouses abound in Beppu, including the popular ones where you can pay to be buried in hot sand. You can see a video of the experience at http://www.japan-in-motion.com/jim/item/mov_243/, and http://www.hakusuikan.co.jp/en/spa/sand-bath.html declares (admittedly with some rather irritating background sounds) that “This Sand Bath in Ibusuki is very unusual throughout the entire world. Bury yourself in the sand comfortably, and have some snooze with a sound of the sea.... After burried in the sand, you can take a bath in big bathhouse, wash off the sand and refresh like... a baby!” It also shows a very convincing photo of blood before and after the treatment…

[For a great online tour of the Challenger expedition, see this Scripps Institution of Oceanography site; for the online documentation of the Challenger reports, see http://www.19thcenturyscience.org/HMSC/HMSC-INDEX/index-linked.htm and this French collection, easily navigable via the PDF titles.]

Sunday sand: critters of Calangute

 

I have a small, but very select, band of arenokleptomaniacs, friends and family who never leave home without small plastic ziploc bags in which to collect sands on their travels - carefully labelled - to be added to my collection. One of my agents, a Dutch friend who had recently been in Goa, brought back a wonderful and very diverse selection from the beaches of the Arabian Sea, and this is one of them. Calangute is primarily a tourist destination, the lure being the usual endless sand and tropical balminess.

It’s clear from simply looking at the sand that it contains much organic debris, fragments and sand-sized grains of shells. But, down the microscope, its true beauty is revealed. Crowding out the scattered rock and quartz grains are countless little spiral shells of foraminifera, the incredibly diverse group of single-celled marine organisms, of which hundreds of thousands of species are known and which occupy essentially every marine habitat known. They are also survivors, boasting an evolutionary lineage that covers hundreds of millions of years. Most of them, like these from Goa, make their shells, or tests, from calcium carbonate and thus are key players in the great game of ocean chemistry. And they are among nature’s most creative and artistic designers, their shells demonstrating a seemingly endless variety of exquisite geometries. Below is one of the stunning illustrations of Ernst Haeckel, the nineteenth-century German biologist, philosopher, and artist – among the thousands of new species that he identified and named were large numbers of foraminifera.

 

But forams are not the only critters in these sands – there are all kinds of biogenic bits and pieces, and, in my microscopic browsing, I happened upon this perfect shell. What is perhaps remarkable is that, in spite of the daily buffeting and grinding of waves and tides, the onslaught of monsoon storms, and the crushing weight of sunbathing tourists, these shells survive intact – built to last. 

Louisiana berms update

 

“Where is the common sense in studying if sand or oil is more harmful to a coast?”

How to begin answering this question? It was posed recently by one of the candidates in the runoff for the Republican contender for the 3rd Congressional District seat: “The people are tired of study after study without any action,” he said.

It’s been a while since I added to my series on “The Great Wall of Louisiana,” but in the meantime the dredges continue their devastation, the political rhetoric grows (something that hardly seemed possible), and the coastal and environmental science fades even further into the background. The fact is that “study after study without any action” is true, but not in the sense the candidate intended: the results and recommendations of many studies by Federal Agencies and coastal and environmental scientists have been completely ignored.

The Baton Rouge Advocate recently published an illuminating article, “Berm controversy rises,” in which they state that “The Advocate requested documents that would show debate about the concept among state officials. None were provided, although some reports and financial records were made available.” The article goes on to say that “Some of the questions are being raised by federal agencies. Those views were not made public during the emergency permitting because of [Army] corps [of Engineers] policy.” They may not have been made clearly public, but they were available: I posted sources that I had dug up (dredged, so to speak) on May 23, May 28 (including extracts from the permit and comments by several agencies), then a summary of the key USGS report, and other sources. The Advocate article goes on to summarise some of these views, for example:

In the U.S. Fish and Wildlife Service’s Aug. 18 comments, Supervisor of the Louisiana Ecological Service Office James Boggs wrote: “Any large-scale threat to the Louisiana coast from the Deepwater Horizon oil will likely have dissipated long before the completion of the berm barrier project.”

“In light of the fact that much of the oil is dissipating and it is highly unlikely that the berm can be constructed within a time frame that will meet the stated objective (i.e., trapping oil), the Service questions the need for continuation of the barrier berm project,” Boggs wrote.

The U.S. Geological Survey reported that sand resources along the Louisiana coastline are scarce.

“The excavation of this material for use in building an emergency berm may compromise future coastal restoration efforts by reducing the sand resources,” the Geological Survey’s report states.

Impact on fish and wildlife
The National Marine Fisheries Service also questions the continuation of the berm project.

Roy Crabtree, regional fisheries service administrator with the National Oceanic and Atmospheric Administration, wrote that portions of the project are in areas of essential habitat for many federally managed species and for some listed as threatened or endangered.

“All these species are known to occur in coastal Louisiana and are susceptible to hopper dredging activity, and in the case of the leatherback sea turtle, it is susceptible to capture or drowning by relocation trawling associated with hopper dredging in the Gulf,” Crabtree wrote.

The source of the dredged sand — shoals off the coast of Louisiana — is also a concern for some scientists. The shoals are the remnants of former river deltas and barrier islands that are now underwater hills of sand.

And yet, Garret Graves, Governor Jindal’s director of coastal activities and a berm enthusiast, “said many of the critics raise questions because they lack information, others are applying data without considering the impact of the oil and still others are just against the idea.”

“There are a lot of people out there that have just decided that the berms are just something they’re going to kick up one side and down the other. I’ve talked to a few of them. These people have very, very little understanding,” Graves said.

The USGS, the EPA, the National Marine Fisheries Service, and so on and so on, “have very, very little understanding”? Who, exactly, did he talk to?

The comments by Crabtree with respect to the threats to the leatherback sea turtle are important. Here’s an extract from the Gulf Restoration Network site a couple of weeks ago (and, interestingly, reproduced on the Dredging Today site): 

In drafting comments responding to Louisiana’s request to continue with and expand the project, we discovered that in a single two week period , the current sand berm project killed at least five threatened Loggerhead Turtles - and the full toll on turtles is likely higher. In fact, one Army Corps’ report indicated large amounts of turtle activity in the area, stating “Many turtles and turtle heads seen in the area in and around the trawling/dredging site.”

But let’s hear from Garret Graves again: “For folks to suggest that they are an environmental hazard, I think those comments are irresponsible.” 

Irresponsible?

As for the effectiveness of the berms so far? “Garret said workers have collected about 700 barrels of oil from the berms on the west side of the river and about 1,500 pounds of oil and oil-covered debris from the berms on the east side.” And the cost and progress of the project? “The state Department of Natural Resources reports that it has written slightly more than $120 million in checks as of Sept. 2 from the $360 million that oil giant BP set aside for the berms….About 3.6 miles of berms have been built, leaving about 31 more miles to be done under the current permit.” I shall refrain from commenting…

And yet Governor Jindal is seeking to expand the permit:

As Jindal attempts to get permits to expand the project — plus more funding to transform the sandy sections, called berms, into longer-term barrier islands…Graves said the plan would be to fill in the areas behind the berms to create a marsh, which would serve as a platform for the additional vegetation and other restoration that would help build up the barrier islands. With the pipes and dredges already in place for the sand berms, Graves said, the costs now would be less than reorganizing the effort down the road.

If it weren’t for the fact that this sorry saga illustrates so well the growing disconnect between science and politics (on both sides of the Atlantic), I think that I’d despair and give up.

"Extinguished by strangers with sand."

Seventy years ago, on the 7th of September, 1940, the London Blitz began – it would continue for eight months. Looking at map of the more than 800 recorded events of that first day and night, I find that an incendiary bomb landed in the street outside what is, today, my apartment, ironically in front of the fire station that was, for a long time, the headquarters of the London Fire Brigade. It’s that fire station building, and the associated pub, that are the only survivors from that time. The Guardian newspaper has a comprehensive online article and associated set of resources on the events of that first day, and it was there that the following quotation caught my eye:

The fire brigade was nearly overwhelmed. At the start of the war, London had just 120 red fire engines and 2,000 motorised pumps. That night's records repeatedly say "Extinguished by handpump" or "Extinguished by strangers with sand."

Sunday sand: up close and personal

 

I’ve written before about the extraordinary life and accomplishments of Ralph Bagnold, “The man who figured out how deserts work.” Back in 2007, I was lucky enough to go on one of my “trips of a lifetime” and follow, as closely as possible given the minefields, in his footsteps and tyre tracks in the Western Desert of Egypt (and bits of Sudan and Libya). Bagnold followed scientific method carefully and scrupulously, building equations from first principles to describe the movement of sand, then constructing experimental tests of those equations in a wind tunnel, modifying and reworking the theory, until it was ready to be further tested in the field. In 1938, he established himself at a base camp at the foot of the cliffs of the towering plateau of the Gilf Kebir in Egypt’s southwest corner and waited for a sandstorm. While he waited, he tested his instrumentation:

 

After several events of sand being dramatically on the move, he had results that, although like all field measurements, imperfect, nevertheless supported and augmented his mathematical and laboratory results: the science of sand transport was set on the foundations that continue to support it today. In 2007, we visited the dune under which  Bagnold had camped 69 years before.

 

The remains of the structures that Bagnold and his companions had built for the camp were still there, but very much the worse for wear. Benzene cans with the Shell logo were still lying around – the desert is kind to such artifacts. 

 

The image at the head of this post shows sand from Bagnold’s dune at various magnifications – typical desert quartz grains, painted with a translucent veneer of iron, many of them rounded by abrasion in the wind but many of them also chipped and angular as a result of those impacts. Look closely at any individual grain, and we see the texture of its surface, a microscopic topography, the physiognomy of the grain. The closer we look, the more complex does that topography become, and there’s a whole sub-discipline of geology that devotes itself to reading the geological runes of grain surface textures, reconstructing the stories that those miniature landscapes have to tell.

A while ago, I was approached by Aspex, a company in Pittsburgh that specialises in bench-top scanning electron microscopes, yet another example of sophisticated technology becoming ever-smaller – see the details here. As part of their marketing campaign, Aspex were offering free electron microscope scans of anything, so, of course, I sent them a few sand grains, including samples from Bagnold’s dune. So, continuing our increasingly detailed scrutiny of individual sand grains, here are some examples:

 

The scales are in microns (also known more officially as micrometers or micrometres), one of which is a millionth of a meter. The sand grain is around half a millimetre across; a couple of typical bacteria would cover the area of the highest magnification image. Altogether, from the photograph of the sand at the left of the image at the head of the post, to this, the highest magnification from the scanning electron microscope, our scrutiny has taken us through, roughly, a multiple of ten thousand times.

Up close and personal, worlds within worlds: William Blake would have been astonished by the scanning electron microscope. I’ll end with other, more accessible views, this time using transmitted light, the illumination behind the grains revealing different aspects of their character….

 

[My thanks to Jeffrey Tabaka at Aspex for arranging to provide the scanning electron microscope images and to Stephen Bagnold for the photograph of his father at work]