Through The Sandglass

Sunday sand: the treasures of Bretignolles

 

Bretignolles-sur-Mer is but one of the many seaside resorts along the Atlantic Coast of France, but for those interested in unusual sands, it’s a special destination: this is one of my favourites and a classic amongst arenophiles. As you walk on to theshore, you can’t help but notice the strange purple-red-rust-black sand piled up at the top of the beach, against the concrete wall. In fact, you can see this band of colour on Google Earth.

 

Look more closely, and you’ll see how this sand contrasts with the more typically coloured grains of the rest of the beach, and how the two conspire to create natural designs sculpted by waves and the receding tide.

  

Pick up a handful of this sand and you’ll be surprised – it’s distinctly heavier than you would expect, and there’s a reason for this. It’s a placer deposit, a concentration of heavier minerals winnowed by storms and dumped at the top of the beach. I’ve written about placers before, particularly in the context of the California Gold Rush; natural processes of granular segregation by waves, tides, and rivers, take heavier mineral grains originally dispersed through the sand and concentrate them – placer deposits are commercially significant around the world for a wide variety of industrial minerals and precious stones, not just gold.

This concentration is clear in the image at the head of this post – whereas the normal beach sand at Bretignolles is dominated, as is so often the case, by clear quartz grains, there are few of these to be seen in the placer sand. Instead, we see a dazzling variety of red, orange, pink, and black grains. So what are these minerals?

Any beach sand represents a recipe of local ingredients: sand formed from the weathering and erosion of rocks exposed along the coast, mixed with the generally even greater volumes of material sampled from the geology of the interior by rivers, flushed down to the coast and then relentlessly distributed by waves and currents along the shore. Bretignolles, although culturally lying in the Department of the Vendée, samples its sand grains from the southernmost outcrops of Brittany. And Brittany has a long and torrid geological story to tell. Without worrying about the details, a glance at the geological map of this part of France reveals the complexity of this recipe:

 

It’s a tangled fabric of colours, each one a different rock type, apparently stirred together and then shot through with faults on all scales. This is the Armorican Massif, named after the old area of Gaul, its geological – and cultural and linguistic - history linked to parts of Cornwall. The tangled fabric is testament to not just one drama of colliding tectonic plates and mountain-building, but two: first, the Cadomian Orogeny (mountain-building event) around 600 million years ago, then the Hercynian or Variscan orogeny. This series of chaotic and complex tectonic events lasted more than 100 million years, creating the Ouachitas and the Appalachians together with much of old Europe, and ended up welding the supercontinent of Pangaea together 280 million years ago.

What we see today in the geology of Brittany are the roots of these old mountain belts – the younger and shallower rocks have been stripped off to reveal the foundations forged in the extreme pressures and temperatures deep in the crust. And it’s these baked and tortured, metamorphic, rocks that the sands of Bretignolles come from.

The red and pinkish colours are grains of garnet, a mineral name that covers a wide variety of compositions – all silicate minerals, but with varying proportions of calcium, magnesium, aluminium, iron, and chromium; those proportions determine the colour. The black grains are iron oxides of various types, among them magnetite (hence much of the heaviness of the sand).

 

There are also grains in this sand that I really can’t identify – metamorphic rocks contain exotic and diverse ingredients. But the “treasure” can be seen in the centre of the image above: bright, sparking blue, sapphire. This is the aluminium oxide mineral, corundum, which also comes in a range of colours, and thus some of these varieties are gemstones: if it’s red, it’s a ruby, blue is a  sapphire.

Of course these sapphire grains (e.g., below, close-up and personal) are not things you would put in a ring that would be appreciated as a gift, but I hope you would agree that they are treasures – and beautiful examples of the stories that sand can tell.  

 

[I was directed to Bretignolles by Carla, a Dutch sand collector to whom I am grateful for this and many things.]

Oil-eating bacteria: a new member of the family brings good news

 

I find fascinating, and many readers also seem to, the role of oil-eating bacteria in the Gulf of Mexico disaster. Fascinating for any number of reasons: not only is the role of such microbes in the normal ecosystem remarkable, but their appetite for hydrocarbons contributes significantly to the removal of spilt oil on the surface and at depth – and equally remarkable is, in reality, how little we know about them. I first described alcanivorax borkumensis back at the beginning of June, with follow-ups a couple of weeks later and then in July. Now, in the interests of updating this ever-evolving theme – and finding the science in the “debate” about what has happened to the oil – here’s some extremely interesting news. Workers at the Lawrence Berkeley National Laboratory have just described their discovery “that microbial activity, spearheaded by a new and unclassified species, degrades oil much faster than anticipated.” The italics are mine.

Here's the Berkeley Lab press release – a noteworthy and, to me at least, astonishing detail is the device used: “Sample analysis was boosted by the use of the latest edition of the award-winning Berkeley Lab PhyloChip – a unique credit card-sized DNA-based microarray that can be used to quickly, accurately and comprehensively detect the presence of up to 50,000 different species of bacteria and archaea in a single sample from any environmental source, without the need of culturing.”

Study shows deepwater oil plume in Gulf degraded by microbes

Aug 24 2010

In the aftermath of the explosion of BP’s Deepwater Horizon drilling rig in the Gulf of Mexico, a dispersed oil plume  was formed at a depth between 3,600 and 4,000 feet and extending some 10 miles out from the wellhead. An intensive study by scientists with the Lawrence Berkeley National Laboratory (Berkeley Lab) found that microbial activity, spearheaded by a new and unclassified species, degrades oil much faster than anticipated. This degradation appears to take place without a significant level of oxygen depletion.

“Our findings show that the influx of oil profoundly altered the microbial community by significantly stimulating deep-sea psychrophilic (cold temperature) gamma-proteobacteria that are closely related to known petroleum-degrading microbes,” says Terry Hazen, a microbial ecologist with Berkeley Lab’s Earth Sciences Division and principal investigator with the Energy Biosciences Institute, who led this study. “This enrichment of psychrophilic petroleum degraders with their rapid oil biodegradation rates appears to be one of the major mechanisms behind the rapid decline of the deepwater dispersed oil plume that has been observed.”

The uncontrolled oil blowout in the Gulf of Mexico from BP’s deepwater well was the deepest and one of the largest oil leaks in history. The extreme depths in the water column and the magnitude of this event posed a great many questions. In addition, to prevent large amounts of the highly flammable Gulf light crude from reaching the surface, BP deployed an unprecedented quantity of the commercial oil dispersant COREXIT 9500 at the wellhead, creating a plume of micron-sized petroleum particles. Although the environmental effects of COREXIT have been studied in surface water applications for more than a decade, its potential impact and effectiveness in the deep waters of the Gulf marine ecosystem were unknown.

Analysis by Hazen and his colleagues of microbial genes in the dispersed oil plume revealed a variety of hydrocarbon-degraders, some of which were strongly correlated with the concentration changes of various oil contaminants. Analysis of changes in the oil composition as the plume extended from the wellhead pointed to faster than expected biodegradation rates with the half-life of alkanes ranging from 1.2 to 6.1 days.

“Our findings, which provide the first data ever on microbial activity from a deepwater dispersed oil plume, suggest that a great potential for intrinsic bioremediation of oil plumes exists in the deep-sea,” Hazen says. “These findings also show that psychrophilic oil-degrading microbial populations and their associated microbial communities play a significant role in controlling the ultimate fates and consequences of deep-sea oil plumes in the Gulf of Mexico.”

Hazen and his colleagues began their study on May 25, 2010. At that time, the deep reaches of the Gulf of Mexico were a relatively unexplored microbial habitat, where temperatures hover around 5 degrees Celsius, the pressure is enormous, and there is normally little carbon present.

“We deployed on two ships to determine the physical, chemical and microbiological properties of the deepwater oil plume,” Hazen says. “The oil escaping from the damaged wellhead represented an enormous carbon input to the water column ecosystem and while we suspected that hydrocarbon components in the oil could potentially serve as a carbon substrate for deep-sea microbes, scientific data was needed for informed decisions.”

Hazen, who has studied numerous oil-spill sites in the past, is the leader of the Ecology Department and Center for Environmental Biotechnology at Berkeley Lab’s Earth Sciences Division.  He conducted this research under an existing grant he holds with the Energy Biosciences Institute (EBI) to study microbial enhanced hydrocarbon recovery. EBI is a partnership led by the University of California (UC) Berkeley and including Berkeley Lab and the University of Illinois that is funded by a $500 million, 10-year grant from BP.

Results in the Science paper are based on the analysis of more than 200 samples collected from 17 deepwater sites between May 25 and June 2, 2010. Sample analysis was boosted by the use of the latest edition of the award-winning Berkeley Lab PhyloChip – a unique credit card-sized DNA-based microarray that can be used to quickly, accurately and comprehensively detect the presence of up to 50,000 different species of bacteria and archaea in a single sample from any environmental source, without the need of culturing. Use of the Phylochip enabled Hazen and his colleagues to determine that the dominant microbe in the oil plume is a new species, closely related to members of Oceanospirillales family, particularly Oleispirea antarctica and Oceaniserpentilla haliotis.

Hazen and his colleagues attribute the faster than expected rates of oil biodegradation at the 5 degrees Celsius temperature in part to the nature of Gulf light crude, which contains a large volatile component that is more biodegradable. The use of the COREXIT dispersant may have also accelerated biodegradation because of the small size of the oil particles and the low overall concentrations of oil in the plume. In addition, frequent episodic oil leaks from natural seeps in the Gulf seabed may have led to adaptations over long periods of time by the deep-sea microbial community that speed up hydrocarbon degradation rates.

One of the concerns raised about microbial degradation of the oil in a deepwater plume is that the microbes would also be consuming large portions of oxygen in the plume, creating so-called “dead-zones” in the water column where life cannot be sustained. In their study, the Berkeley Lab researchers found that oxygen saturation outside the plume was 67-percent while within the plume it was 59-percent.

“The low concentrations of iron in seawater may have prevented oxygen concentrations dropping more precipitously from biodegradation demand on the petroleum, since many hydrocarbon-degrading enzymes have iron as a component,” Hazen says. “There’s not enough iron to form more of these enzymes, which would degrade the carbon faster but also consume more oxygen.”

 

[Image at the head of this post from the press release and the Terry Hazen group. The results of this research were reported in the journal Science (August 26, 2010 on-line) in a paper titled “Deep-sea oil plume enriches indigenous oil-degrading bacteria.” Co-authoring the paper with Hazen were Eric Dubinsky, Todd DeSantis, Gary Andersen, Yvette  Piceno, Navjeet Singh, Janet Jansson, Alexander Probst, Sharon Borglin, Julian Fortney, William Stringfellow, Markus Bill, Mark Conrad, Lauren Tom, Krystle Chavarria, Thana Alusi, Regina Lamendella, Dominique Joyner, Chelsea Spier, Jacob Baelum, Manfred Auer, Marcin Zemla, Romy Chakraborty, Eric Sonnenthal, Patrik D’haeseleer, Hoi-Ying  Holman, Shariff Osman, Zhenmei Lu, Joy Van Nostrand, Ye Deng, Jizhong Zhou and Olivia Mason.]

Ephemeral charts - and a new bit of France

 

I have always found great pleasure in the fact that, among my ancestors, there was something of a tradition of map-making and engraving. This was the profession of two of my great-great-uncles in the nineteenth century, James and George, and my great-grandfather, Arthur, continued the family tradition well into the twentieth century. I have a number of examples of their work, but maps are ephemeral things: the natural and man-made world changes, and new maps quickly supersede the old – after all, do any of us keep road maps from ten years ago? OK, we all have GPS these days, anyway, but my point is simply that of a personal frustration that more maps by the various Wellands don’t survive – I have a large framed version of the splendidly named “Welland’s New Plan of London,” but it’s a copy that my father obtained from the British Library and I’ve never been able to find an original.

This cartographic ephemerality is particularly vivid in nautical charts, and I was struck by this when I was discovering the dynamics of Sable Island in the course of writing the book. Sable Island, one of the world’s most extraordinary and dangerous islands, emerges from the North Atlantic 160 kilometers offshore from Nova Scotia, and originates from the constant churning of and re-working of glacial sediments:

Sable Island is long and thin, around 40 kilometers from tip to tip (although measurements vary) and just over a kilometer across at its widest point. It lies roughly east-west, its crescent shape looking like a thin-lipped smile in the middle of the ocean. But the smile is deceiving: the island is simply the tip of a vast iceberg of sand, the much, much larger Sable Island Bank. Just beneath the ocean’s surface is a rolling topography of moving sand stretching up to 14 kilometers north to south and perhaps 30 kilometers east to west. The island lies at the meeting point of three major ocean currents, the Labrador current moving southward, the St. Lawrence current moving eastward, and the Gulf Stream on its way north. This interaction causes the waters of the Atlantic to swirl in a great counterclockwise pirouette around the island; but bottom currents, controlled by the tides, swirl clockwise. The result is a complex of ridges and valleys of sand running roughly northeast to southwest. This is a shape-shifting topography, the ridges migrating 50 meters every year, and changing rapidly during the frequent storms. Nautical charts are barely worth the paper they are printed on.

So it’s that last statement that is really my theme here (and a contributing factor to Sable Island’s candidacy as a “graveyard of the Atlantic",” although there are others). The one example of my Great-Grandfather’s nautical charts that I have is of an estuary on the east coast of England, just north of that of the Thames – a portion is shown at the head of this post (north to the right). I have to admit that I relish some of the names - “Foulness Sand,” “Buxey Sand,” “Dengie Flat” (separated from the “Ray Sand” by the “Hoo Outfall”); “Bachelor Spit” lies next to “Swire Hole.” The chart probably dates from around 1910 (the magnetic declination shown is 1907). Estuaries are ever-changing landscapes in the constant battle between rivers, tides, and currents, and I can’t help but wonder how the shifting sands have changed this landscape in a hundred years. I found an online source of modern charts (emphatically annotated as not for navigation), a part of which, corresponding to my great-granddad’s, looks like this:

 

It’s a delight to see that all the names are still there, but, even allowing for the lower level of modern detail, close examination reveals changes to the underwater landscape: the Buxey Sand seems to have grown, filling in “The Hole” at its western end, and the shape of the coast around Colne Point has changed significantly, largely, it would seem, as a result of human activity. Inspection of historic Google Earth images reveals that a new sandbar has appeared off Mersey Island, and, to my pleasure since I had recently written about such things, a beautiful hooked spit has been growing near the mouth of the River Colne: 

 

The shape-shifting  nature of a minor estuary on England’s east coast brings me on to greater things: for well over a year now, a new bit of France has endured in the mouth of the estuary, the largest in Europe, of the mighty Gironde River (mighty both in its sediment transport capacity and in its vital role in producing the wines of Bordeaux). The Phare de Cordouan is the oldest lighthouse in France, completed in 1611, and continues to serve a vital role, for the area around is a treacherous terrain of rocky outcrops and sandbanks situated right in the entrance to the estuary:

 

The lighthouse has been described, with typical French understatement, as the “Versailles of the sea,” “the king of lighthouses,” “lighthouse of the king,” and the eighth wonder of the world. In early 2009, after an Atlantic storm (“Klaus”) had abated, an entirely new island had appeared six nautical miles from the coastal town of Royan (celebrated as the place where President Sarkozy built sandcastles as a child), and close to the lighthouse. It had an area of around 4 hectares (“two-and-a-half football pitches” at high tide, much more at low tide – this is an approximate measure, so which particular brand of football hardly matters). The “island with no name” or "L'île Mystérieuse" quickly became an ecological celebrity and a destination. Colonisation by flora and fauna took place rapidly, but, to the consternation of the local authorities, this “fragile ecosystem” was threatened by the influx of boatloads of partiers. Unfortunately, it was also threatened by the same forces of nature that created it – early this year, the season’s great storm (variously named “Cynthia” or “Xanthia,” either one of which sounds oddly benign for a tempest) cut the island in half and wiped out the ecosystem. But "L'île Mystérieuse" survived.

 

The tensions between the scientific and romantic communities on the one hand, and the party-loving hordes on the other (“terfeurs,” ravers, have recently been active on the island), continue. A French online news site recently described a visit to the island that has also been referred to as “Tahiti” in reverential ways: “ une véritable énigme,"  “un mirage paradisiaque,” and “des allures de mystérieux mirage marin” hardly need translation; but then we find that “On se prend à rêver un instant que l’empreinte de son pied dans le sable mouillé est le premier du genre humain à cet endroit précis” – “one can dream for an instant that one’s footprint in the wet sand is the first of humankind in this exact place.” I can’t help but be reminded of the quintessentially French question: “this is all very well in practice, but how does it work in theory?”

The state has yet to recognise the island, either with a name, or on a chart. I have examined both Google Earth and the French “Geoportail” site of aerial photographs and, of course, the imagery has not caught up with recent events. But what these sources do show is the routine sedimentary turmoil of such a dynamic setting; I’m not sure of the exact dates of the two images below, but the dramatic differences are immediately apparent (the lighthouse is at the end of the linear causeway, bottom centre left):

 

How to deal with "L'île Mystérieuse" is the subject of an ongoing debate (see recent coverage in the UK press). Whether the island or the debate will endure longer remains to be seen – it is, after all, a sandbank, and the enthusiasm for conservation has to be tempered by the fickleness of nature. But then again, this is the first natural addition to French territory in many centuries, indeed, as reports note, since loss of the fabled island of Armotte just to the north of the Gironde estuary, a Gallic Atlantis where pagan depravity led to its destruction in an “appalling cataclysm.” Those reports raise the possibility that "L'île Mystérieuse" will eventually be included in the geography books. And nautical charts? Perhaps yes, but, as Great-Grandfather Welland might have asked, for how many editions? 

[photo of the island and the lighthouse from the article in the Independent]

Sunday Sand: Marshall Beach, San Francisco

 

I’ve had the idea of starting a regular Sunday post simply showing off the character of a different sand each week. And, following on from my recent visit to the San Francisco Bay area, where better to start than on Marshall Beach, in the shadow of the Golden Gate Bridge.

I took the bus (San Francisco’s public transport system is a delight, and the 511.org website a brilliantly designed guide to it) to the toll plaza parking at the south side of the bridge, and wended my way along well-signed trails, through the massive remains of the military installations; the Presidio had been a strategic military complex since the days of the Spanish and was handed over to the National Park Service in 1994 – they have done a typically great job of rehabilitation and making the place a pleasure to visit. Among the efforts of the Park Service has been the remarkable installation of stairways on many of the trails that lead down and through the landslipped bluffs to the shore:

 

(Since, for reasons that escape me, I neglected to take any photos en route, perhaps preoccupied with my cranky knees and the prospect of the return journey, these are by Ingrid Taylar from the “Batteries to Bluffs” guide at about.com:San Francisco).

The rocks along the trail are chaotic and rotten, disintegrating, crumbling, and sliding – and most of them are serpentinite, the much-vilified and possibly about-to-be-illegal State Rock of California; perhaps I should have worn breathing apparatus. Will the Park Service be required to remove the steps since they wind amongst what is portrayed as a public health hazard? Throwing caution to the winds, I stopped several times to admire the gloriously varied hues of these rocks – apple-green, blue-green…

At the foot of the crumbling and colourful bluffs is Marshall Beach.

Rocks along the shore tell the tortured story of California’s geological past: they are part of the Franciscan mélange. The word is French for a mixture, a term that bestows some class on what are, in fact, very messy rocks (the sort of thing that field geologists refer to as “fubrite,” the etymology of which I shall leave up to your imagination to deduce). The mélange is, indeed, a mixture, lumps of different rock types, large and small, embedded in a swirling, fractured, vein-shot matrix. This and the serpentinite, together with the other ingredients of the rocks in the, area tell the torrid story of the chaos of subduction 100 million years ago, oceanic crust and mantle, along with deep-sea sediments, bulldozed beneath, and scraped up on to, the edge of the old North American continent to form the tangled tectonic scrap heap that would be California.

The sand of Marshall Beach is, in itself, a microscopic museum of this geology, a kaleidoscope of colourful grains of different rocks and minerals, including the sparkling quartz grains that quite likely were born in the granites of the Sierras, weathered out and washed down into the sands and gravels that also contained gold, were flushed into the San Francisco Bay by the wholesale manmade erosion of the Gold Rush, and eventually swept out to the coast to end their journey in my ziploc bag.

[See also Andrew Alden’s guides to the local geology at About.com, and, for more detail, the USGS field guide to the Geology of the Golden Gate Headlands.]

Bed load: as inscrutable as ever

 

One of the many arguments in favour of good old-fashioned libraries – the bricks and mortar, hardcopy, poking-around-in-the-stacks  variety – is the un-measurable element of serendipity: things you happen upon when looking for something else. I was recently relishing the joys of the Geological Society Library here in London, in quest of material for a post that I have yet to write, when exactly such a diversion occurred. Taking down from the shelf the recent issue of Sedimentology that I was after, I naturally scanned the contents and was struck by a completely different title: “The partitioning of the total sediment load of a river into suspended load and bedload: A review of empirical data.” It admittedly does not sound particularly gripping, but I knew it was a tricky geological conundrum and thought that perhaps, finally, here would be a definitive breakthrough; my hopes were quickly dashed, but the paper did fulfil my enjoyment of the apparently simple things that remain elusive, that continue to defy our best attempts to measure and quantify them.

The news today is filled with dramatic and tragic images of rivers in flood, devastating lives and livelihoods. Rivers are engines, whose dimensions and power increase by orders of magnitude when they hurtle out of control. And, in doing so, they are gargantuan conveyor belts of sediment transport, shifting unimaginable volumes of material from the continents to the oceans – along the way, ironically, renewing the fertility of agricultural land after first devastating it. The engine operates in three different ways to carry its sediment load: by rolling and bouncing grains, pebbles, and boulders along its bed, by swirling smaller grains into almost continual suspension, and by carrying soluble minerals dissolved in the water. The last, the dissolved load, is simple to measure, the suspended load relatively simple, and the bed load extremely difficult. Measures of the sediment load of rivers commonly are for the suspended load only, but the bed load is huge. And all of these numbers are only averages—a river in flood will carry orders of magnitude more sediment than it does on a normal day.

Understanding the sediment load of a river and how it works is much more than simply a matter of scientific enquiry – it’s vital for managing soil erosion, infrastructure design, reservoir sedimentation, and agriculture. Yet we are not very good at it. As I mentioned, the dissolved and suspended loads are relatively easy to measure, the bed load extremely difficult – and, in times of flood, downright hazardous. Yet the bed load is critical. A few years ago, I stood next to a river flooding out of the Pyrenees (the photos at the head of this post show its normal, tranquil, state and in flood). Behind the roaring cacophony of the water racing by was a deep undertone, a thundering and clunking sound: this was the voice of the bed load, of boulders and cobbles rolling and bashing their way along the river bed. Floods in this part of France are common and destructive – the photo below shows a river’s bed load deposited in the town of Vernet les Bains (ironically, “Vernet the Baths”) after what was possibly the European rainfall record, a metre in 24 hours in 1940.

 

Historically, the challenge of measuring bed load and its dramatic variability has been approached empirically, by attempting to devise a relationship between the (measurable) suspended load and the associated transport along the bed. Albert Einstein’s son, Hans, produced the classic equation, still used with modifications today, when he was a professor at the University of California, Berkeley (his father had advised him against embarking on this field of study because of its complexity). In the early 1950s, several pieces of work produced empirical tables listing bed load as a percentage of total and suspended load under different conditions, particularly the material of the river bed; these tables, reproduced in the paper I discovered in the library (full reference below), look like this:

 

As an attempt to cram a wildly variable natural phenomenon into some kind of quantifiable and useable scheme, they are obviously of only limited use – just look at the variability in the percentages even when a number of variables are ignored. I read the start of the abstract of the paper with interest:

The partitioning of the total sediment load of a river into suspended load and bedload is an important problem in fluvial geomorphology, sedimentation engineering and sedimentology. Bedload transport rates are notoriously hard to measure and at many sites only suspended load data are available. Often the bedload fraction is estimated with rule-of-thumb methods such as Maddock’s Table, which are inadequately field-tested.

But then my expectations were dampened when I read the abstract’s conclusion:

 For sand bed rivers, the bedload fraction may be substantial (30-50%) even for large catchments. However, available data are scarce and of varying quality. Long-term partitioning varies widely among catchments and the available data are currently not sufficient to effectively discriminate control parameters.

In other words, we’re effectively no closer today to tying down and understanding a river’s bed load than we were more than fifty years ago. However, the paper is a really interesting review of the problem, and it adds some new high-quality data from a river in the mountains of Austria, “for which high temporal resolution data on both bedload and suspended load are available.” But, “The available data show large scatter on all scales.”

And here, just to illustrate the mind-boggling range of measurements of how rivers behave, are two graphics from the paper. First, bed load transport rates as a function of suspended load transport rates (in kilograms per second – note that the scales are logarithmic):

 

and then a plot of the fraction of the total load that is transported as bed load (this varies between zero and one) versus the associated suspended load concentration (which varies between 0.3 and 10,000 parts per million). Random scattering, anyone?

 

OK, it’s not random, but for me it’s a fascinating example of the elusive and complex character of apparently simple natural processes – and ones that are important to us.

[The reference for the paper is: Turowski, Jens M.; Rickenmann, Dieter; Dadson, Simon J.. 2010 The partitioning of the total sediment load of a river into suspended load and bedload: A review of empirical data. Sedimentology, 57. 1126-1146. doi: 10.1111/j.1365-3091.2009.01140.x]

The Navigator's maps in the sand

 

The obituary page in The Economist, always, appropriately, the final section of its content, is intentionally idiosyncratic, celebrating lives not always covered by its broadsheet colleagues. Catching up after my recent travels, I was struck by the image (above) at the head of an obituary from last month, titled “Pius Mau Piailug, master navigator, died on July 12th, aged 78.” Reading the column, I was even more struck by this extraordinary man and his accomplishments – in this, the age of technology, there are people and skills, knowledge, that challenge our conventional wisdom, and are to be treasured. Mau Piailug was one of these people:

IN THE spring of 1976 Mau Piailug offered to sail a boat from Hawaii to Tahiti. The expedition, covering 2,500 miles, was organised by the Polynesian Voyaging Society to see if ancient seafarers could have gone that way, through open ocean. The boat was beautiful, a double-hulled canoe named Hokule’a, or “Star of Gladness” (Arcturus to Western science). But there was no one to captain her. At that time, Mau was the only man who knew the ancient Polynesian art of sailing by the stars, the feel of the wind and the look of the sea. So he stepped forward.

As a Micronesian he did not know the waters or the winds round Tahiti, far south-east. But he had an image of Tahiti in his head. He knew that if he aimed for that image, he would not get lost. And he never did. More than 2,000 miles out, a flock of small white terns skimmed past the Hokule’a heading for the still invisible Mataiva Atoll, next to Tahiti. Mau knew then that the voyage was almost over.

On that month-long trip he carried no compass, sextant or charts. He was not against modern instruments on principle. A compass could occasionally be useful in daylight; and, at least in old age, he wore a chunky watch. But Mau did not operate on latitude, longitude, angles, or mathematical calculations of any kind. He walked, and sailed, under an arching web of stars moving slowly east to west from their rising to their setting points, and knew them so well—more than 100 of them by name, and their associated stars by colour, light and habit—that he seemed to hold a whole cosmos in his head, with himself, determined, stocky and unassuming, at the nub of the celestial action.

Sharing breadfruit

Setting out on an ocean voyage, with water in gourds and pounded tubers tied up in leaves, he would point his canoe into the right slant of wind, and then along a path between a rising star and an opposite, setting one. With his departure star astern and his destination star ahead, he could keep to his course. By day he was guided by the rising and setting sun but also by the ocean herself, the mother of life. He could read how far he was from shore, and its direction, by the feel of the swell against the hull. He could detect shallower water by colour, and see the light of invisible lagoons reflected in the undersides of clouds. Sweeter-tasting fish meant rivers in the offing; groups of birds, homing in the evening, showed him where land lay.

He began to learn all this as a baby, when his grandfather, himself a master navigator, held his tiny body in tidal pools to teach him how waves and wind blew differently from place to place. Later came intensive memorising of the star-compass, a circle of coral pebbles, each pebble a star, laid out in the sand round a palm-frond boat. This was not dilettantism, but essential study; on tiny Satawal Atoll, where he spent his life, deep-sea fishing out in the Pacific was necessary to survive.

Nonetheless, the old ways were changing fast. After Mau, at 18, was made a palu or initiated navigator, hung with garlands and showered with yellow turmeric to show the knowledge he had gained, no other Pacific islander was initiated for 39 years. Alone, he went out in his boat with the proper incantations to the spirits of the ocean, with proper “magical protection” against the evil octopus that lurked in the waters between Pafang and Chuuk, and with the wisdom never to get lost—or only once, when he was wrecked by a typhoon and spent seven months, with his crew, waiting to be rescued from an uninhabited island.

As a palu, however, he could not allow his skills to die with him. He was duty-bound to pass them on. Hence his agreement to captain the Hokule’a. That voyage, which proved that the migration of peoples from the south and west to Hawaii was not accident, but probably a deliberate act of superlative sea- and starcraft, transformed the self-image of Hawaiians; and it changed Mau’s life. Suddenly, he was in demand as a teacher. Patiently, pointer in hand, one leg tucked under him, he would explain the star compass to new would-be navigators; but he allowed them to write it down. He knew they could never keep it all in their heads, as he had.

Much of what he knew, of course, was secret. The secrecy was serious: when he spoke of spirits, his smiling face became deadly sober and even scared. To a very few students, he passed on “The Talk of the Sea” and “The Talk of the Light”. By doing so, he broke a rule that Micronesian knowledge should remain in those islands only. It seemed to him, though, that Polynesians and Micronesians were one people, united by the vast ocean which he, and they, had crisscrossed for millennia in their tiny boats.

In 2007 the people of Hawaii gave him a present of a double-hulled canoe, the Alingano Maisu. Maisu means “ripe breadfruit blown from a tree in a storm”, which anyone may eat. The breadfruit was Mau’s favourite tree anyway: tall and light, with a twisty grain excellent for boat-building, sticky latex for caulking, and big starchy fruit which, fermented, made the ideal food for an ocean voyage. But maisu also referred to easy, communal sharing of something good: like the knowledge of how to sail for weeks out on the Pacific, without maps, going by the stars.

 

 

[For readers, like me, slightly challenged by the geography of Pacific Islands, here is a quick guide – I love the fact that looking up Satawal on Google maps seems to produce a blank blue map, whatever the magnification used. And, on Google Earth, the location delivered by a search for the island is blank blue sea – Satawal is, in fact, to the east. Images of Mau Piailug from the University of Hawaii Manoa’s Traditional Micronesian Navigation pages, by Steve Thomas. The obituary at The Economist can be found on its website – I have deemed my subscription to cover reproducing it here. Short videos of Piailug can be found here and here, and a longer description of his epic voyage is on the website of the Polynesian Voyaging Society.] 

Why is a National Wildlife Refuge still being dredged and bulldozed?

 

Admittedly, there is a debate going on as to the amount of oil remaining in the system from the Gulf of Mexico disaster, but it seems generally agreed that surface oil is greatly diminished. In that case, why is the State of Louisiana continuing to destroy the Chandeleur Islands? 

The image above is from a series taken last month by Rob Young, one of the leading voices of scientific reason opposed to the lunatic scheme, a voice that I have quoted often in previous posts; all these remarkable photos (and ones of Dauphin Island) are viewable at http://psds.shutterfly.com/sandberm/. And, in spite of the greatly diminished, if not essentially disappeared, threat, the “successful” project continues:

The sand berm project is continuing to operate successfully," said Garret Graves, the governor's director of coastal activities. "All sand berm construction has been paid for by BP, and we continue to expect BP to fund construction until the project is completed. (The Times-Picayune, August 5)

An editorial at Houma Today from a few days ago, titled “Monkeying with the coast,” began with “Pop quiz: When do politicians quote scientists? When the scientists agree with the politicians, of course.” The term “monkeying” comes directly from Rob Young: “The thing about monkeying around like this is that there are unintended consequences. What we do know for sure is that projects like this will change wave patterns, they’ll change the way the sand and the sediment moves, and there will be negative impacts.” The rationale for this view has been laid out in detail by coastal scientists from the start of the “great wall of Louisiana” project, and is being ignored today as it has always been. The editorial concludes:

In fact, given a choice between self-serving politicians and people with scientific knowledge, I will always choose the latter for deciding how to protect our coast.

The scientists don’t have some sinister ulterior motive.

They don’t want oil washed ashore any more than our politicians do. But when politicians trot out a plan that doesn’t fly with the experts, the experts owe it to themselves and to us to speak out against it.

And when those public officials are monkeying around with our fragile coast, we need the warning.

And yet the dredging and the bulldozing continues – why? The image at the head of this post is worth examining. What do we see? An isolated sand bank, a remnant of a barrier island system devastated and dismembered by Hurricane Katrina. We see bulldozers shifting vast volumes of sand around, sand supplied from neighbouring shallow waters. Do we see any sign of berms connecting neighbouring islands? Do we see any neighbouring islands? How can this possibly be described as any kind of effective barrier? 

Dr. Stephen Cofer-Shabica, an oceanographer in South Carolina, is quoted as follows:

The Chandeleur project is totally futile and a waste of resources, and I can’t believe they are still doing it. That’s what I find totally unfathomable. There’s oil floating around underwater, that has been dispersed and these barrier islands, as constructs, will not have any effect on that oil at all……From an oceanographic perspective, this was biologically destructive, especially when you start digging up the bottom in shallow water, and building these barrier islands. Louisiana is in a precarious position anyway because of the subsiding that is happening in the delta, and on top of that you have worldwide sea-level rise, so it has two physical factors that are working against its marshes. So building barrier islands to presumably keep oil out, amid rising sea levels, makes no sense.

 

The photos above, also from Young’s site, illustrate further the absurdity and brutality of this project. And remember that this is the Breton National Wildlife Refuge, for crying out loud. It’s “the second oldest refuge in the country and was 100 years old on October 4th, 2004. President Theodore Roosevelt heard about the destruction of birds and their eggs on Chandeleur and Breton Islands in 1904 and soon afterward created Breton NWR.”

Why does the project continue? Well, let’s note, without comment, a couple of reports from its beneficiaries (other than the political ones). First, from Dredging News Online:

The Times Picayune reports that although the Macondo oil well is now sealed and new estimates showing reduced oil sheen on the surface of the Gulf of Mexico, Govrnor Bobby Jindal's enthusiasm for the massive $360 million sand berm barrier project he has championed has not diminsihed.

A spokesman for Governor Bobby Jindal told the newspaper that the US$360 million sand dredging project should be finished in October.

With BP money, the state's dredging contractors in the past two months have completed a portion of the project by moving about 5 million cubic yards of sediment to create narrow artificial islands to block oil moving east and west of the mouth of the Mississippi River.

Jindal's oil spill response team and leaders of coastal parishes say the berms are capturing oil that might otherwise have flowed into Louisiana's inlets, marshes and wildlife refuges.

"The sand berm project is continuing to operate successfully," said Garret Graves, the governor's director of coastal activities. "All sand berm construction has been paid for by BP, and we continue to expect BP to fund construction until the project is completed."

and then from the Great Lakes Dredge and Dock Corporation:

Douglas B. Mackie, President and Chief Executive Officer, said, "Great Lakes had a strong first six months, achieving 19% growth in operating income and a 37% increase in net income attributable to Great Lakes, compared with a strong 2009 first half. Earnings improved due to the higher volume of domestic work and favorable contract margins, particularly on beach projects, that more than offset a decline in foreign dredging activity. In addition, we continue to see encouraging signs in the demolition business as quarter-end backlog levels are more than twice that of a year ago.

"During the quarter, we were contracted to assist in the construction of sand berms off the Louisiana coast in response to the Deepwater Horizon oil spill. This capital work is expected to be an important contributor to our third quarter's revenue.”

Well, certainly $360 million is a lot to monkey around with…..

 

[Photos reproduced under the creative commons license, copyright and courtesy of the WCU Program for the Study of Developed Shorelines]

Sands of the San Francisco Exploratorium

When I bought my ticket for the Exploratorium, I asked, of course, where there were exhibits that used sand. After initially pointing to one close by, the guy behind the counter looked at me and asked if I wanted to avoid such things. Two thoughts immediately sprang into my mind: this could be a fine example of creative, lateral, thinking but could it be that he had recently encountered a visitor who had specifically expressed this desire? Someone who wished to be given an itinerary around the exhibits that kept them as far away from sand as possible? Someone with an allergy to the stuff? I quickly made it clear that, no, such things were the primary focus for my visit, and received helpful directions. Not that they were really necessary – within a few steps of the entrance I encountered ten exhibits whose attraction depended on the behaviours of granular materials.

The closest, the one which had been first pointed out, contained a strong pair of magnets and a good supply of iron sand – like all the Exploratorium entertainments, play was encouraged. It turns out that the iron sand was extracted from Ocean Beach, on the coast just south of San Francisco:

 

Then I encountered “Seismic sand,” a clear, rotatable, disc filled with fine sand, next to which hung a large drumstick. I was encouraged to beat rhythmically on the disc and observe the patterns formed in the sand – so I did, with gusto. Reflecting the fluid-like behaviour of the sand, the sign encouraged comparison with earthquake liquefaction, something that I thought a bit far-fetched; but it went on to say that the patterns formed are due to “the complex interactions of the flowing sand with the vibrational waves of the air inside and the motion of the walls of the container itself. The dynamics of this process are not well understood” (my emphasis – I always like such statements, when faced with something created so apparently simply).

 

My next encounter was with a dune and ripple machine, blowing sand around – the observer could manipulate the fan. The structures of windblown sand were introduced in the associated description.

 

Next to the dunes was a device called “Landfall,” enabling the creation of “a miniature landscape in sand.”This is somewhat difficult to describe, but see the photos below. A large transparent sphere is divided in half by a panel that contains holes which can be opened or closed using the silver knobs around the circumference. The whole thing can be rotated by cranking a handle – rapidly or slowly depending on the energy and age of the cranker – and the sand poring from one hemisphere into the other creates endlessly varying granular landscapes: below, a good approximation of talus slopes or even alluvial fans; other possible landforms were invoked in the accompanying description. This was really quite compelling to watch – I had to wait my turn for a while as a young cranker expressed his determination to get all of the sand into one hemisphere (a challenging task that eventually proved too much for his attention span and I was able to move in).

 

Next, “Rift Zone.” By pressing a button, air can be jetted from below into a pile of very fine sand and the resulting craters and slumps are dramatic. However, this was billed as simulating “some of the geological features associated with rift zones” – including lava extrusion: fun though it was, I thought this a little misleading:

 

And then: avalanches! A stunningly-designed container (of which I was quite envious) demonstrated the same processes of self-segregation and stratification that I have described from my own kitchen physics experiments. Kitchen experiments, avalanches, making cross-bedding, complexities of sand flowing out of a funnel – endlessly entertaining (well, I find it so – as did any number of visitors I observed at play in the Exploratorium).

 

Of course, playing in the sand often involves making patterns, and three of the exhibits were designed exactly for that. A wonderful shape-shifting vibrating pile of sand that responded in compelling but unpredictable ways to visitor interaction, and several spinning discs on which designs could be generated using a variety of tools – or, most popularly, simply one’s fingers.

  

And, finally, acoustics: two separate illustrations of Chladni patterns. I wrote a bit about these in my book:

In the late eighteenth century, a lawyer, musician, and scientist in Leipzig, Ernst Chladni, was determined to make sound waves visible. He succeeded in doing so by covering glass or metal plates with sand and drawing a violin bow across the plates’ edges. The vibrations provoked the sand grains into a frenetic, leaping dance, not just randomly: they arranged themselves like Scottish dancing groups into formations. The patterns were highly variable—stars with different numbers of points, crosses, complex intersecting arcs. The science of acoustics and the physical manifestation of sound was born… The patterns produced in Chladni’s experiments were as much about the material on which they were produced as about the sand itself, but the patterns seem to relate to underlying natural behaviours. All granular materials indulge in some extraordinary pattern making.

But this was the first time I had been able to play around with these patterns myself, so play I did. The exhibit provided several differently shaped plates which could be interchanged, and a simple means of varying the vibration frequency of the plate. The accompanying panel gave useful hints as to appropriate frequencies to try with different shapes – the results were quite dramatic:

 

And, next to the vibrated plates was (above, right) a truly excruciating further demonstration of Chladni’s patterns, this time produced using the original method, pulling a bow across the edge of the plate. It worked, but the process reminded me too closely for comfort of the days when my son was learning to play the viola.

Now of course there is far, far, more in the Exploratorium beyond the sand devices. There’s a terrific new section on perception errors and cognitive biases, a working cloud chamber, biological and microscopic phenomena… all too much to play with in one afternoon. But whether or not you have kids, a visit is highly recommended if you’re in the Bay area – it’s a great “museum” that makes science accessible as well as mysterious, compulsively interactive, and, above all, FUN.

And, when you’re all played out, mentally exhausted by the mysterious behaviours of granular materials, you can simply stroll outside, cross the road, and sit on the beach with a great view of the Golden Gate Bridge. It’s all magic.

 

(A side note: I was surprised not to find my book in the store - but I decided that they must have sold out)

Thoughts from planet Google

Colourful bikes, a tyrannosausrus rex sculpture that has evolving relationships with pink plastic flamingos, buildings identified by the fundamental physical constants, food never more than thirty feet away, and pool tables in the office: where else could this be but Google's headquarters? Scifoo 2010 has just ended, and I have to report that it was a rather extraordinary and mentally exhausting experience. The assembled intellectual weight was sufficient to threaten induced seismicity here in Sunnyvale California: a clutch of Nobel Laureates, prominent research scientists and students from all fields and all parts of the world, media folk, assorted other luminaries - and me. When my wife reviewed the list of participants, she observed that it appeared to be dominantly leading scientists but with a few wildcards - I, she commented, would fall into the latter category; I took this as a compliment.

As an "unconference," the entire scheduling of sessions was left until the first evening, and took place via a chaotic rush to grab a large coloured post-it note, scribble down your session title, and slap it onto a space on huge whiteboards with times and rooms. Somehow or another, it worked:

There were occasional challenges where a room with a designated capacity of sixteen held an audience of forty, but again it turned out not to be a problem, merely an opportunity for close-packed intellectual critical mass. The one thing it did have in common with conventional conferences was parallel sessions - really difficult choices that left all of us wishing that we lived in a multiverse (the topic of some of the sessions). For my session, I was fortunate to hook up that first night with Judith Curry, Chair of the School of Earth and Atmospheric Sciences at Georgia Tech, and Lenny Smith, Professor in Statistics at the London School of Economics and Senior Research Fellow of Pembroke  College, Oxford; both are leading figures in the world of climate science, and their presence provided a whole new dimension to my agenda. The close-to-forty people who attended (or crammed themselves into the sixteen-capacity room) engaged in a highly stimulating discussion - no issues were resolved, but it was serious fun. 

The spirit of Scifoo is that participants try to attend sessions on topics that they are completely unfamiliar with. This was not a problem for me. I am now aware that space is an emergent phenomenon, as is gravity, and that gravity has an entropic origin. Please don't quiz me on the details. I watched movies of previously blind mice successfully navigating a maze after having restorative genes delivered by viruses. I engaged in a discussion of "The future of the author," joined a debate about how to construct a virtual reality climate change game, ruminated on prediction markets, and learned the three rules for being a successful mad scientist. 

The steam from my poor brain is now diminishing, but there remains a lot to think about and contacts to follow up on. The entropic origin of gravity, however, I shall probably not dwell on further.....