Through The Sandglass

"I'm real concerned about the beach"

 

So declared Dennis Dare, a Manager of Ocean City, Maryland, after the conspiracy of a nor'easter and the remnant of tropical storm Ida wrought havoc along the coasts of the northeastern US over the last few days. His concern was well placed - much of the beach simply wasn't there any more, instead there was a twelve-foot cliff marking the extent of relentless wave erosion. Ocean City engineer Terry McGean, after inspecting the scene, is reported as saying “We lost a lot of dune. We lost a fair amount of beach. We’ve seen worse. Certainly, the idea is that we lose sand and not buildings, so it did its job. Now we get everybody rolling to get it back together”; he went on to describe how when it comes time to reload the beach with sand next summer, it’s going to be more expensive and take more sand than they’d planned for. He said the beach lost between 25-50 percent of its dunes.

"Reload the beach" ? I suppose he must be referring to the time-honoured futility of beach nourishment.

The press reports contain many dramatic images and I shall simply reproduce some of my favourites here, with quotations from the accompanying descriptions.

 

"Coastal community leaders said Saturday they were crossing their fingers that the waves would send enough sand back up onto the beaches that human assistance wouldn't be needed to finish the replenishment, shoring up the resorts in time for the economically vital summer."

 

"In Delaware, tides washed out dunes, leaving several feet of water and 3 feet of sand along state Route 1. Transportation officials say it may take two days to clear the sand."

 

"Several vessels carrying hazardous cargo broke loose from their moorings in Virginia during the storm. Crews were working to stabilize a 570-foot barge carrying containers of chemicals in the Sandbridge area of Virginia Beach. Work crews boarded the barge and were riding out the storm with it, hoping it would run aground and could be towed away when the weather improves. A similar fate awaits a 700-foot oil tanker that broke loose and ran aground on a sandbar in the James River in Newport News, Va."

 

"But even if another storm were to hit today, the sand washed away from the dunes will still be of some help, creating a larger near-shore sandbar system that serves to break the waves' energy as they pound the coast. That effect was apparent Friday afternoon, Tony Pratt, Delaware's shorelines and waterway administrator said. "The waves really were breaking quite a distance from the dune by the end of the day ... and losing a tremendous amount of their energy," he said. 'I like it better when the dune is whole, [but] that sand is still serving a great service. ... It's not like a total loss.' "

"Beach replenishment is a costly endeavor. A project earlier this year in Dewey Beach alone cost $6 million. "We're hopeful that Mother Nature will do her job," said Carol Everhart, executive director of the Rehoboth Beach-Dewey Beach Chamber of Commerce. Since 2001, the Army Corps and others have spent $100 million pumping sand from the ocean onto Delaware's beaches. Building sea walls will cost much more -- a sea wall built in Galveston, Texas, cost $10,000 a foot."

 

"State and local beach officials have credited the dunes with defending their towns' homes and boardwalks from the storm's wrath.

Taking an opposite view is Orrin H. Pilkey, emeritus professor in the Nicholas School of the Environment at Duke University and author of "The Corps and the Shore" and this year's "The Rising Sea," which he co-authored.

Pilkey said it would be a huge error for Delaware to ignore science and not plan for the inevitable approach of climate change and rising seas. He pointed to the damaging Ash Wednesday storm of 1962, when the Army Corps of Engineers erected a dune along the shore in Ocean City, Md., and issued an advisory to restrict development inland of the protective barrier. But homes and hotels eventually moved oceanside, on top of and across the dune.

'The town paid no attention to it -- it had no teeth,' Pilkey said. 'Money speaks -- so away we went.' "

[I couldn't possibly comment further on all this - the images and the quotations speak for themselves. Many of the images are from http://www.delawareonline.com/, and http://www.nj.com/, credits Patti Sapone, Robert Sciarrino, Chuck Snyder, Laura Emmons]

Arenaceous sporting trivia - the baseball World Series

 

My daughter and her grandfather, both in Philadelphia, will probably, to put it mildly, have less than kind words for me when they see this post. For the Phillies (last year's champions) were beaten in the baseball World Series last night by the New York Yankees - of all teams, it had to be the Yankees (for non-North American readers, I have appended some brief explanatory notes at the end of the post). Angst, tears, and rage in Philadelphia, exuberant celebration in New York. But, for Through the Sandglass, it's just another opportunity, to point out the ubiquity of my topic - in the continuing tradition of my daughter's Simpsons challenge.  

For a start, like many sporting surfaces, the construction of a world-class baseball field relies on first-class sand. The iconic diamond, its grass and its surrounding "dirt," are made from specialty materials. Go to the website of the Beam Clay company of Great Meadows, New Jersey ("Your 'one-stop source' for America's baseball and sports turf surfaces and supplies!") and you will be bewildered by the choice of over 200 products for the construction, care, and maintenance of your dream infield - for example, their "Premium infield mix":

Made from uniform orange sand and red Beam Clay® with our special binding process that reduces wind and water erosion. Doesn’t separate and blow away! Doesn’t become dusty in stadiums! With proper maintenance, provides firm traction without tracking, good drainage while retaining playing moisture, distinctive reddish/orange color, works up readily, no separation of ingredients, long lasting, safe to slide on - for safe, attractive, consistent professional quality baseball diamonds.

The nature and performance of the materials used for the batter's and catcher's boxes are particularly important, but as in the action of a game, the pitcher's mound has to be a focus of attention. A good history of the pitcher's mound and how to construct one can be found here; the ingredients and recipes vary little - although the climatic environment of the stadium is important. This particular summary is from http://www.baseball-almanac.com/:

The mix used to build the pitcher's landing area (and often the batter's box and catcher's box) should have a significant concentration of clay to provide the necessary stability to resist degradation from increased traffic. A good material will be about 40% sand, 20% silt, and 40% clay. If necessary, you can mix individual components together. Just be sure that individual components are evenly distributed throughout the material.

     A quality infield material will have a lower concentration of clay than the pitcher's mound. The infield skin should be moist and firm, not hard and baked dry. To achieve firmness, an infield mix should not be too sandy. An infield mix with greater than 75% sand causes unstable footing for ballplayers and increases infield skin maintenance problems. A sandy infield will create low spots more quickly and is more likely to create lips at the infield skin/turf interface. Ideally, the infield mix should be between 50% and 75% sand and 25% to 50% clay and silt. A combination that has been successfully used is a 60% sand, 20% silt, 20% clay base mix (sandy clay loam to sandy loam). The silt and clay give the mix firmness. If the mix contains too much silt and clay, compaction and hardness become a problem.

So, a skilful (and well-paid) pitcher can stride out to his patch with confidence that its consistency will provide a reliable foundation for his art. And, in the case of Mariano Rivera ("Mo"), who finished off the Phillies last night and has been called "the best closer in the history of the game," his appearance on the field - if the game is in New York - is accompanied by a loud rendition of Metallica's "Enter Sandman" - "we're off to never-never land." It is said that this is by no means Mo's favourite song, but that it is played on his entry because when he comes into a game, you can pretty much put it to bed. If you wish, you can see a video of this from last night's game at http://www.wikio.com/video/1925785.

And then, of course, there's sand lot baseball. And plastic baseball-shaped bottles that can be filled with coloured sand - but one example of a wide range of such things; I couldn't possibly comment on their artistic merit - but I suspect that Andrew Clemens will not be rolling in his grave..... 

 

Notes for non-American readers:

1. The "World Series" has been widely derided by non-North Americans as being no such thing, since no countries other than the USA and Canada can compete for it. In order to combat such accusations of sporting arrogance, it has often been declared that the name originates from the original sponsorship of the championship by the newspaper, The New York World, early in the last century. Indeed, my (American) wife firmly corrected me to this effect a long time ago. But it's a myth - the "World Series" is, and always has been, exactly that (see Snopes). Not that I would in any way revert to my earlier derisive remarks ..... Always remember that the other life of Steve Gould, the extraordinary and revered evolutionary biologist and writer, was as a devoted and passionate baseball fan - of the Yankees. 
2. I would no more attempt to explain baseball to non-Americans than I would cricket to baseball fans (both are challenges equivalent, in Shakespeare's words, to "numbering the sands and drinking the oceans dry.") Suffice it to say that both games are very much like the classic description of a soldier's life - long periods of boredom interrupted by brief moments of terror (well, generally not exactly terror, but action, something to actually engage the senses and the emotions).
3. In the later stages of a game, the starting pitcher is often replaced by a specialist finisher - a "closer" like Mariano Rivera.
4. A baseball signed by Mo and with the words "Enter Sandman" can be purchased from http://www.mlbfansite.com/ for a mere $399.99 (knocked down, so to speak, from the original price of $501.86).
5. Herewith, from http://www.baseball-almanac.com/stadium/baseball_field_construction.shtml, a simple illustration of the layout of the diamond and the infield. From now on, you're on your own.
   
   
   
   
   

Too much, too little, and often in the wrong place

 

It rose out of the omnipresent sand of a natural island, and there remains a thin layer of the ocher substance almost everywhere: on the canopied grandstands, on the brilliantly lighted hotel at the edge of the track, on the seats and in just about every corner of the Yas Marina Circuit in Abu Dhabi.

So went the start of a New York Times article on yesterday's finale to the Formula One Grand Prix season. Small armies of workers were sweeping the sand right up to the last minute and yet, as The Walrus and The Carpenter observed, it's essentially an impossible task. Holding an extravaganza of highly sophisticated but delicate technology in this kind of environment brings many challenges. As the article went on to comment

 It may play havoc with the engines of the cars and it will change the grip, lap by lap, for the drivers, even affect the lenses and other camera mechanisms belonging to the hundreds of photographers and journalists who will document the final race

For races in neighbouring Bahrain, it's long been a problem, as explained by Red Bull’s technical director Gunther Steiner:

You have to be aware that it can get in to every part of the car. It literally sandblasts the car every time it goes on track and gradually erodes all the surfaces and the cooling fins on the radiators.

Unique measures are taken to protect exposed suspension and other parts of the cars, and specially designed air filters have to be used. And then there's the problem with grip and tyre selection - after all, a motor race in which the drivers have to go slowly in order to stay on the track - and avoid whole sections of it because it's covered in sand - detracts somewhat from the sporting attraction. David Coulthard, the now-retired driver, was quoted before the race as saying

It does seem to be very sandy. When I followed a car the amount of stuff coming out the back was incredible. What that does is two things: one, it makes the driver pay the price if he goes a bit off line, which is good because it favours ability, but it is also makes people not want to take the risk in overtaking. Sand on your tyre takes a good lap to be cleared out.

And so it proved. It was largely a risk-avoidance race with drivers clearly sticking very closely to a single driving "line," conspicuously steering clear of the rest of the track - and often running into problems when they didn't. Grains of sand influencing a sporting spectacle and, as The Times Online concluded, "Whoever wins the inaugural Abu Dhabi Grand Prix on Sunday will be fêted in a nation that can afford to buy its heroes — but the victorious driver might feel his name is not written in history, but in the sand."

But if the sport was less than inspiring, the setting made up for it. This was the inaugural race at Abu Dhabi's latest example of construction extravagance. Ras Island, just down the coast from the preposterous artificial island developments of Dubai, was but a sandy expanse a mere 30 months ago (see the Google Earth image at left of the image at the head of this post). It hardly seems to have been a natural island, but rather 25 square kilometers of coastal desert, sandbanks, and sabhka (salt flats) carved out and isolated from the mainland by manmade waterways. After several tens of billions of dollars, and the efforts of tens of thousands of workers, things have changed. The image below is of the hotel complex across the track (as night falls, as it did for the Grand Prix, the whole thing glows in a succession of changing colours) and at the right in the image at the top is the way the whole place will look when finished.

 

The strange red object in the centre of the header image is "Ferrari World," the largest indoor theme park on the planet, "like a megalomaniac’s pleasure dome" in the words of the NYT. Yas Island will boast  20 hotels, 3 theme parks, a "Super Regional mall", golf courses, several marinas, and commercial and residential developments. You can read the full specs at the developer's website, but in case you don't here's a sampling of the exuberance on this "island of dreams":

There will be a Super Regional Mall that will house famous retail brands from
around the world in over 500 stores and 4 floors including lifestyle, fashion &
boutiques.
• There will also be room for a complete town centre concept, contained in a
number of adjacent buildings and built under a 88,100m2 roof
• The Yas Mall will have one of the largest free standing roofs in the world,
showcasing 296,000m2 of the world’s best retail space
• Adjoining the Yas Mall will be will be Abu Dhabi’s first Multi-purpose Retail
Park (100,000m2)
• Three major department stores will be accommodated.
• A large hypermarket covering an area of 17,000 m2

 What I have not been able to determine is how much concrete goes into this monster (one hotel used 45,000 cubic metres of it, the racetrack 225,000) or, indeed, where all the sand came from for that concrete; presumably, as in neighbouring Dubai, local sources of non-desert sand were used (the windblown stuff being too rounded and smooth for good concrete), and the local natural sand budgets consequently profoundly changed. But it's not just the natural sand budgets. Although sand prices around the world have fallen during the economic crisis, they peaked in 2007 at more than $40 per ton, and sand supplies were becoming difficult. The Economist recently ran an article (pleasingly titled "The hourglass effect") that began:

“LOOKING for sea-sand for reclamation project in Singapore. Prompt reply is greatly appreciated.” Many such pleas can be found on Alibaba.com, a popular Chinese trading-website. Malaysia banned sand exports as long ago as 1997. Indonesia followed suit in 2007 on environmental and, some say, political grounds. Ever since, it has become harder for Singapore to secure supplies for its booming construction industry and sea-fill plans.

Singapore has turned to Cambodia and then Vietnam for its sand, but both have now banned exports. It seems that Myanmar may be the replacement supplier, so I will see my favourite material propping up, through, of course, western contractors, a loathsome dictatorship. The need is clear for a more widespread development and use of advanced forms of concrete that not only use less sand, but also can be manufactured without the associated emissions. And considering that every man, woman, and child on the planet "consumes" forty times their own weight in concrete every year, the sooner the better.

And finally, still on sand budgets and still in the news, today's Guardian newspaper carries a piece titled "Tide turns again for Cancún in shifting sands row." The 800,000 cubic metres of sand that were used to replace beaches washed away by Hurricane Wilma a few years ago lasted only a few months, and the current project is only the latest in a series of failed attempts at beach nourishment.

A huge project to replenish eroded beaches in Mexico's main Caribbean coastal resorts, including Cancún, has been suspended after legal action by environmentalists.

Campaigners claim the $75m (£45m) plan – involving taking 6.2m cubic metres from a sandbank just off Cozumel island, 50 miles from Cancún, to hotel beaches – is based on incomplete assessments.

Critics say dredging the sandbank will alter currents and damage ecosystems, including coral reefs and breeding grounds for species such as the queen conch. They also fear Cozumel will become more vulnerable to hurricanes. "It's absurd. We understand it is necessary to fill out the beaches but it needs to be done without sacrificing other places," said Alejandra Serrano of the Mexican Centre for Environmental Law.

But Rodrigo de la Pena, president of the Hotel Association, criticised the delay: "We cannot sell ourselves as a place of sun and sand, if we don't have the sand."

Alejandra Serrano is right - it's absurd. But then so many things are, including much of what I've just written about .....

Coastal change and saving sand - the state of the art

 

In my talk earlier this week, Ten Things We Don't Know About Sand, number 6 was "How coasts work." Now of course we know the basics, but coastal systems are so complex and dynamic that the details elude us. I used my postcards of French sandbanks and the fascinating work of Rob Holman at Oregon State University and his Argus program movies to show just how dynamic our coasts are and how difficult it is to describe or model them in a way that not only creates a detailed understanding of their processes, but therefore a means of sensibly managing them and planning for the future. And then I read the announcement of a new USGS publication, Saving Sand: South Carolina Beaches Become a Model for Preservation, in which the introduction includes the following:

Changes in the morphology of coastal landforms and patterns of sediment movement have been stud­ied for over a century, but, in general, scientists have only a rudimentary understanding of the processes that drive coastal change.

Sometimes I think that there must be something to the idea of synchronicity...

The full report, downloadable from the USGS link above, is a case study of the state of the art of our evaluation of how a single stretch of coast works. It's the summary of a six-year multidisciplinary study of the northeastern coast of South Carolina by the USGS in cooperation with the South Carolina Sea Grant Consortium (SCSGC). "The main objective of the study was to determine the geologic and oceanographic processes that control sediment movement along the region’s shoreline and thereby improve projections of coastal change." The stretch of coast studied is the "Grand Strand" segment, three headlands south from Cape Hatteras (where the lighthouse was heroically moved after decades of futile attempts to stop natural processes). It's only a 100 km length of coast, but it's a complex system of beaches, barrier islands, back barrier lagoons and tidal inlets. The variation of shore types is illustrated in the figure below, from the report.

 

And the dramatic rates of shoreline change, both long-term and short-term, are shown in the figure below. Note that the scale is in meters per year, ranging from +10m/yr to -10m/yr, over just this short length of coast.

 

The study is truly interdisciplinary, and employed a wide-ranging set of tools. Sidescan sonar, and the acoustic back scatter that it generates, allowed mapping of sediment types. Ground penetrating radar and different sub bottom profiling techniques revealed the structure and sedimentological/geomorphological history of the sub-seafloor geology. Current meters, sediment traps, wave-height sensors, and other instruments were attached to sturdy metal frames  and anchored to the seafloor to record constantly changing environmental conditions and sediment flux. The operations (below, right) were clearly more successful than those of the traverse and triangulation party of L. P. Raynor in 1924 (below, left, photo from http://www.photolib.noaa.gov/).

 

I won't attempt to describe here the results of this extraordinary programme of research, but they are fascinating. Substantial contrasts in coastal processes arise from sand supply and availability. Sand-starved segments of the coast are characterised by exposure of older sediments and sedimentary rock (as old as Cretaceous in age, from 70 million years ago) and respond to wave and storm action very differently from sand-rich segments. Beach profiles and the dramatic changes to those profiles vary enormously both with sand availability and with exposure to seasonal change and storm events. Sediment budgets and individual littoral cells, along with their specific sediment sources and sinks, change rapidly along the coast and on a scale smaller than we have previously been able to define. Sediment flux is hugely variable with the time of year and wave and weather conditions, displaying complete reversals of transportation direction. The illustration below is just one example of the detailed analysis of shallow offshore processes, sand ridges in this case lying just oceanward of the popular resort of Myrtle Beach.

 

And popular - never mind populous - describes this entire stretch of coast, and the work described in this publication attempts to address the thorny issues of future management of a coast that has seen profound changes as a result of human activity. The entire profile - and the associated sedimentary processes - of much of this shoreline has been fundamentally changed by development and all the sea walls, beach armouring, and attempts at "beach nourishment" that go along with it. But look at the rates of shoreline change illustrated above, and the scale of the challenge becomes clear. Shorelines move - that's what they do. And they do it on our time-scales. And they'll do it regardless of our puny bits and pieces of engineering. They may do it slowly but inexorably, day-in, day-out, or they may do it overnight - for example, as a result of Hurricane Hugo in October 1989 (another anniversary this month, along with the Loma Prieta earthquake), illustrated dramatically in the "before and after" photos of the aptly named Folly Beach, down the coast from Myrtle Beach, shown below (again from the amazing resource that is the photo library at the NOAA).   

 

In a 2002 report titled Coastal Sprawl: The Effects of Urban Design on Aquatic Ecosystems in the United States (written, very appropriately, by Dana Beach of the South Carolina Coastal Conservation League), we read the following:

Coastal counties cover 17 percent of the land area of the United States. Coastal watersheds, as described by the Department of Agriculture, represent just 13 percent of the nation’s acreage. By any measure, the coastal zone is a small part of the country, but it is home to more than half of America’s citizens. Moreover, today’s coastal populations are just the tip of the iceberg. Over the next 15 years, 27 million additional people—more than half of the nation’s population increase—will funnel into this narrow corridor along the edge of the ocean.

And population growth is but a subset of a broader problem that results from rising sea levels, the evolving economic and regulatory challenges, and environmental changes. I'll finish this post with a couple of quotes from the press release for the humbly-titled USGS Circular 1339 - I recommend downloading it - it's a cracking read.

“Effective beach preservation requires knowing the beach’s sand budget and understanding the geology that constrains it,” said U.S. Geological Survey lead scientist Walter Barnhardt. “It takes a systematic approach and strong partnerships at all levels of government with neighborhood associations and universities to keep a beach from simply washing away.”

“The comprehensive nature of this study -- considering the geologic framework, behavior and driving processes regionally -- has resulted in a remarkable baseline for better managing our beach and near- shore resources,” said Paul Gayes, Director of Coastal Carolina University’s Center for Marine and Wetland Studies.

“From inventory of potential future beach nourishment sand resources, to distribution of important hardbottom fish habitat, to models of beach behavior, this study forms the starting point for many present and future efforts. This work is regularly cited as a model approach and result for similar studies and efforts around the country,” said Gayes. 

To "around the country" I might add "and around the world."

The Bayeux Tapestry - the quicksand scene

 

My daughter is a great fan of The Simpsons (recently celebrating their 20th anniversary), and enjoys challenging anyone to name any topic for which she cannot quote an episode in which that topic featured. Sometimes, I feel as if I'm getting that way about sand, given the diversity of contexts in which it shows up, but I'm really not up to her professional level. However, until recently, if someone had challenged me to link the Bayeux Tapestry (which is not, incidentally, a tapestry, but more of an extravagant piece of embroidery) and sand, I would have been stumped: but not now.

I recently had the experience of seeing the Tapestry for the first time. The word "spellbinding" is not one I use often, but it seems the only way of describing it. The Tapestry, all 70 meters (230 feet) of it, is displayed in low light to preserve its extraordinary colours, and this adds to the magic as you walk along the story. It's an ancient graphic novel, an elongate comic book, almost an animation; you half expect to see Spiderman intercepting the Norman invaders, or the Sandman attacking their fleet. Such thoughts did not detract from my sense of wonder, but my reverence was briefly tested when I spotted Harold riding along with a hawk on his arm (as, I suppose, such noble folk generally did in those days); I was suddenly struck by a memory of my father reciting to me the comic monologue from music hall days (does anyone reading this remember Stanley Holloway?) of the Battle of Hastings, in which Harold was routinely depicted "on his 'orse with his 'awk in his 'and." Chuckling would have seemed entirely inappropriate, so I controlled myself.

But, back to the point. The early scenes depict Harold being captured in France by Duke William and, having sworn allegiance to him and giving his guarantee that he would not declare himself king, taking off on a campaign with William against a revolting member of the local aristocracy. In doing so, they had to pass by Mont St. Michel and cross the River Couesnon. Now in those days, the river was still behaving naturally, since it was long before human interference changed the regional sedimentology (see my piece on the massive experiment underway there). And the river contained quicksands. The scene that I've reproduced at the head of this post shows Norman horses struggling in the quicksand and Harold saving a couple of soldiers by dragging them out by hand (he carries one on his back). The Latin description reads "hic Harold Dux trahebat eos de arena" - "here Duke Harold pulled them from the sand."  The round hill with the structure on top of it (upper left of centre) depicts Mont St. Michel.

The story goes on to describe how Harold went back on his word and declared himself King, thereby incurring the wrath of William, who proceeded to invade England and defeat the Saxon army at the Battle of Hastings, in the course of which Harold was shot in the eye by an arrow:

And after the battle were over

They found 'Arold so stately and grand,

Sitting there with an eye-full of arrow

On his 'orse with his 'awk in his 'and.

And thus was our vocabulary doubled - but no need to sweat or perspire over that. 

Liquefaction, boils, and volcanoes - sand's role in the Loma Prieta earthquake.

 

Candelstick Park famously survived the earthquake of October 17, 1989 for one simple reason: its foundations were firmly anchored to solid bedrock. But for large areas of central California, the advice against building a house on sand was dramatically and tragically justified. Areas built on young sands and silts, or on reclaimed land, were fine until the waterlogged sediments were shaken - all cohesion and strength in the sediments was lost and they turned to liquid, in the same way that apparently firm patches of beach suddenly suck at your wiggling feet. Liquefaction, this loss of strength in water-saturated sand, is notorious for being often the major cause of severe damage as a result of an earthquake; the sand not only becomes like a liquid but compacts and expels its water. The foundations of structures sink, rotate, and deform, with catastrophic consequences - in the Loma Prieta earthquake some buildings in San Francisco foundered to the point where their third floors were at ground level. The earthquake that devastated the region around Bhuj in northwestern India in 2001 was one of the most damaging in the country’s history. Twenty thousand people were killed and the havoc caused more than $3 billion of damage, much of it as the result of liquefaction - huge cracks in the earth appeared, and water and sand erupted in volcanic fountains as the ground collapsed back on itself. This fickle behaviour of granular materials is the subject of intensive research by engineers and physicists - and microbiologists. As I described earlier, a humble soil-dwelling bacterium, bacillus pasteurii, can make sandstone out of loose sand, gluing the grains together in a way that offers promise for offsetting the threat of liquefaction.  

 

As in Bhuj, liquefaction during an earthquake also shows up in bizarre ways. Layers of sand below the ground surface will liquefy and, under the pressure of the overlying sediments, will exploit any fissure or other line of weakness to flow upwards and burst out on the ground surface as an eruption of sand and water. Known variously but descriptively as sand volcanoes, boils or blows, these can appear anywhere. The image at the head of this post shows a sand volcano that erupted during the Loma Prieta earthquake in the median of Interstate 80 west of the San Francisco-Oakland Bay Bridge toll plaza. The images below are of sand-inundated fields after the Loma Prieta event (left) and, right and below, the Imperial Valley earthquake of October 15 1979 (this seems to be a good week for California earthquake anniversaries).

 

A principle cause of damage by liquefaction is the phenomenon of lateral spreading as the liquid sand spreads out, clearly demonstrated in the photo below (also after the Loma Prieta earthquake) where the road surface has been torn apart by the movement of underlying sand from right to left.

 

And liquefaction was also amply demonstrated in the most powerful series of earthquakes to strike the lower 48 in recorded history—not in California, but in New Madrid, Missouri, between 1811 and 1812. New Madrid at that time was, fortunately, a small town of four hundred inhabitants, none of whom were aware that they lived above an ancient system of deep fractures in the Earth’s crust beneath the Mississippi River Valley. The fractures do not exercise themselves very often, but when they do it is with extreme violence. In the early hours of December 16, 1811, the terrified residents were awoken by violent shaking, accompanied by an appalling roaring sound. They later reported that the surface of the Earth moved in waves and that cracks opened in the ground from which water and sand erupted. One resident, Eliza Bryan, wrote that “the surface of hundreds of acres was, from time to time, covered over in various depths by the sand which issued from the fissures, which were made in great numbers all over this country, some of which closed up immediately after they had vomited forth their sand and water”

If we excavate a sand volcano and examine its plumbing, the sand-filled fissures through which the eruption took place are revealed. This is again analogous to volcanic eruptions of molten rock, where a volcano is fed via underlying cracks through which the magma forced its way. When the molten rock cools and solidifies, these filled feeder cracks are called "dikes", often harder than the surrounding rock and now forming long walls across the landscape. The examples below, cutting across the Namibian desert, record the igneous activity associated with the opening of the southern Atlantic Ocean (photo by the author).

 

The same process, on a more modest and cooler scale, can be seen below sand volcanoes, where the fissures are plugged with sand, silt, and mud. We see these things too in the geological record - clastic dikes (since they are formed of clastic, fragmentary, sediments0 cutting through the surrounding rock. They record past episodes, sometimes on a large scale, of sediment liquefaction. The examples below come from the Badlands National Park of South Dakota (from a good article by the University of Nebraska at Omaha, Dept. of Geography and Geology). These things, for obvious reasons, are sometimes also referred to as injectites.

 

And then there's Sodom and Gomorrah. We are often tempted, for dramatic purposes, to compare the destructive power of natural events such as earthquakes to the biblical demise of the twin cities. Ironically, work by David Neev of the Geological Survey of Israel and K.O. Emery of Woods Hole Oceanographic Institution, together with research by engineers and geologists in the United Kingdom, has suggested that, assuming the cities existed at all, they may well have been destroyed by earthquakes and liquefaction. The area around the Dead Sea, the likely location for Sodom and Gomorrah, lies across the boundary of two rapidly shifting segments of the Earth’s crust and has experienced significant earthquakes over recorded history. Lying below sea level, it is also the ultimate destination of vast volumes of sand and mud, and in many of these ancient layers are the telltale signs of violent water expulsion from the sediments. The photos below show two examples - a sandstone dike on the left and, on the right, incredible folding of the sand and mud layers as a result of sliding like a crumpling table cloth. Altogether, these forensic clues point to an obvious culprit for the destruction. But what about the fire and brimstone? Bitumen, natural asphalt or tar, was much prized during ancient times for medicine, the caulking of boats, and the preservation of mummies, and sulphurous bitumen, together with lighter oil, has for thousands of years been leaking from fractures around the Dead Sea, seeping into the ground and the water. All that would be required would be gas leaking along with the oil and a spark as the ground catastrophically gave way—fire and brimstone?

So, from the Loma Prieta earthquake to Sodom and Gommorah - wherever will sand take us next?

[There is lots of information on the internet and the geoblogosphere about the Loma Prieta anniversary; Andrew Alden on About Geology has been collecting personal stories of the event. For liquefaction, there is, as always, no better resource than the USGS - go to their website and enter "liquefaction" or sand plus "volcanoes" or "boils" or "blows" and you'll find excellent articles and images; for images of the Loma Prieta earthquake, go to the USGS gallery] 

Earth Science Week - sand and the nine big ideas

 

This is Earth Science Week, in the US at least. It's an idea that deserves, through globalisation or international intellectual contagion, to be celebrated worldwide. Sponsored by the American Geological Institute, and supported by a consortium of earth science organisations, it is also underpinned by the Earth Science Literacy Initiative funded by the National Science Foundation:

The Earth Science Literacy Initiative (ESLI).... has gathered and codified the underlying understandings of Earth sciences into a succinct document that will have broad-reaching applications in both public and private arenas. It establishes the “Big Ideas” and supporting concepts that all Americans should know about Earth sciences. The resulting Earth Science Literacy framework will also become part of the foundation, along with similar documents from the Oceans, Atmospheres and Climate communities, of a larger geoscience Earth Systems Literacy effort.

The primary outcome of the Earth Science Literacy Initiative is a community-based document that clearly and succinctly states the underlying principles and ideas of Earth science across a wide variety of research fields that are funded through the NSF-EAR program, including Geobiology and Low-Temperature Geochemistry, Geomorphology and Land-Use Dynamics, Geophysics, Hydrologic Sciences, Petrology and Geochemistry, Sedimentary Geology and Paleobiology, and Tectonics.

It goes (I hope) without saying that the fundamentals of Earth Science Literacy are principles that all human inhabitants of our planet should be familiar with - a utopian aspiration perhaps, but it would arguably make our planet a better place. The fundamentals have been distilled into nine "Big Ideas," each with its own set of supporting concepts, and the summary and guide can be downloaded from the website as a pdf. And it's a compelling document; an Earth Science literate person is defined as someone who

• understands the fundamental concepts of Earth’s many systems

• knows how to find and assess scientifically credible information about Earth

• communicates about Earth science in a meaningful way

• is able to make informed and responsible decisions regarding Earth and its resources

As I read through the nine Big Ideas (and being the arenophile that I am), I was struck by the way in which the stories that sand has to tell can form a theme, a narrative thread that weaves through each of the ideas, illustrating and developing. So below are the nine Big Ideas, each one illustrated by sand, together with links to posts on Through the Sandglass that are but a minor sampling of those stories. This is, on the one hand, something of an indulgence, a sort of retrospective of this blog so far, but, on the other hand, I would like to think that it might be an inspiration, a different, and entertaining, route to Earth Science Literacy. 

1. Earth scientists use repeatable observations and testable ideas to understand our planet. And a large variety of scientific principles are harnessed to reveal the complexities of the earth system. 

Whether it's in the field or the laboratory, as providing vital testaments to the Earth's history or revelations on surface processes and the bizarre behaviours of granular materials, sand and sandstones provide crucial evidence and insights. Sedimentary structures allow reconstruction of past environments and events, a typical integration of fundamental physics, engineering, mathematics, and fieldwork led to our first understanding of how deserts work, and analysis, through granular physics, of the underlying laws of natural systems sheds light on a wide range of phenomena. 

2. Earth is 4.6 billion years old. And throughout its history enormous changes have occurred through gradual and catastrophic processes.

The age of our planet is determined from meteorites and lunar materials, but the oldest bits and pieces formed on the earth itself are sand grains - zircons from Australia dating back more than 4.2 billion years. And zircon grains have many tales to tell of our planet's tumultuous history of change. And then the entire sedimentary record of the earth's history, incomplete and variable as it is, represents the fundamental ledgers of the saga.  

3. Earth is a complex system of interacting rock, water, air, and life.

Whether inorganic in origin, formed from the disintegration of rocks under the assault of atmospheric weathering, or biogenic, formed from shell and other organic debris, sand tells the stories of chemical and hydrologic cycles, energy and material transfer, and mass balances of natural materials. The size of sand grains influences the appearance of the entire planet.

4. Earth is continuously changing.

Sand, by its very nature, is perhaps the most dynamic of natural materials, and geological change on a human timescale is daily illustrated by shape-shifting bodies of sand on our coasts, in our oceans, and in our rivers and deserts. 

5. Earth is the water planet.

And sand is a ubiquitous participant in the great game that water plays in earth processes. Go to the beach and watch the game in action in miniature, or wonder at the huge scale of marine sand transport, the complexity of coastal processes, or the changing dynamics of rivers (with or without human interference).

6. Life evolves on a dynamic earth and continuously modifies earth.

Evolution is a fact. Sand preserves the evidence and can drive ongoing evolution today. Microorganisms are the most widespread, abundant, and diverse group of organisms on the planet, and many of them spend their lives in the company of sand grains. Our beaches host biodiversity possibly greater than that of the rain forest; bacteria turn sand into sandstone, and countless critters build their homes from sand. And then there are the provocative ideas on the interactions between organic and inorganic evolution.

7. Humans depend on earth for resources.

And sand represents a huge resource in countless ways. Electronics, concrete, and precious minerals are but a few examples of sand as a resource - and think how much of our water and hydrocarbons reside in the pore spaces between the grains of sand and sandstone reservoirs.

8. Natural hazards pose risks to humans.

The residents of New Orleans or Samoa whose houses were filled with sand following hurricane Katrina and the recent tsunamis are only too aware of this. The good folk of the Red River Valley, desperately filling sandbags during the floods of earlier this year know all about natural hazards. Desert towns around the world face the threat of moving sand every day. But careful earth science investigation of past catastrophes - for example, tsunami forensics - can help us understand these risks and prepare for future events.  

9. Humans significantly alter the earth.

Boy, do we ever. Earth Science Week this year is dedicated to climate change, but there are endless other examples of our footprint. We dramatically change sediment budgets, altering our coasts on a daily basis; we completely disrupt the natural dynamics of rivers and their sediment transport role. And we do these things often for the most trivial and short-term reasons.

Two tourist lessons in sand dynamics

A few days ago, I described the fractal sand landscapes on the beach of Cap Ferret on the Atlantic coast west of Bordeaux. The swirling sand banks that shape-shift around the cape are but part of the great drama of shifting sand around the Bay of Arcachon and southwards past the great dune of Pyla, the largest in Europe. I left Cap Ferret and navigated around the bay to visit the dune where I found a tourist attraction not much less teeming than that of Mont-Saint-Michel (my previous post). Getting to the dune required passing through endless stalls selling the predictable claptrap and tat, but I did find a good selection of postcards that showed aerial views of the dune and the offshore sandbanks. I bought several, but it was only later, when I laid them out, that I realised how vividly they illustrated the real-time dynamics of this great sand system. Each postcard view was taken at a different time (although, irritatingly, not documented) – and every one is visibly and dramatically different. One is shown at the head of this post, the others below, together with the Google Earth view – a lesson in the futility of nautical charts in the arenas of the great games that sand plays.
 

I also found, amongst the claptrap, large numbers of “sand picture” souvenirs, plastic rotatable frames within which lurid varicoloured sand is set in an oil of some kind – a sort of arenaceous lava lamp. Turn the frame and the sand drifts down to create a new “landscape.” I bought one of the least lurid and I have to admit that I have enjoyed experimenting with it. As shown below, I have created some vivid cross-bedding reminiscent of my kitchen physics experiments I described back in April. So, search among the tourist tat and you can find lessons in marine sand dynamics and the behaviour of granular materials!

 

[On the base of my sand landscape generator, I found the website of its maker, Baz-Art]

Mont-Saint-Michel: a massive sedimentology experiment

  The bay of Mont-Saint-Michel, in the coastal corner of France between Normandy and Brittany, boasts the fourth-largest tidal range in the world – up to 14 meters (46 feet) and the sedimentary drama to go along with it. It is an incredibly complex system. The tides carry sand and silt into the bay and leave much of it behind, augmented by the sedimentary loads brought down to the bay by the three rivers that drain into it. Roughly 700,000 cubic meters of sediment are added to the bay every year – it is, quite naturally, silting up (or, more attractively in French, experiencing ensablement – sanding up). As a result, the iconic World Heritage Site of the monastery towering above its isolated rock is increasingly losing its magnificent isolation and becoming united with the mainland. But this natural process has been greatly exaggerated by human meddling over the centuries and the rhythms of the bay profoundly changed and subdued. The natural processes operate on a scale far beyond that of any human endeavour, but it is possible to mitigate the effects of our meddling and restore the bay to at least close to its unhindered condition and allow natural ensablement to take its course. And that is exactly what is going on today in the bay, after years of preparatory work and research by a syndicate of authorities and institutions – a grand experiment so that Mont-Saint-Michel “ recovers pride of place as the central feature of the Bay, amid a seascape of sands constantly being reshaped by tidal and river water.”

Mont-Saint-Michel began as an isolated rock remaining emergent from the bay as rising sea levels inundated the land following the end of the last ice age; it was periodically connected to the mainland by a natural spit of sand, a tombolo. But then, in 708 so the story goes, St. Michael approached the bishop of nearby Avranches, Aubert (later also a saint) and demanded that a monastery be built on the rock. Foolishly, Aubert ignored this request, finally setting about the task only after the irritated angel had burned a hole in the bishop’s head with his finger (now there’s a warning about procrastination and disobeying orders). The monastery and then abbey grew up over the centuries and then declined; after the French revolution, it became a prison that welcomed, among many anti-republicans, Victor Hugo – he described the tide as coming into the bay “with the speed of a galloping horse.” Along with this tide came the human one – pilgrims both religious and touristic. Today, it is the most-visited site in France outside Paris – three million people visit each year. It was teeming even in mid-September when I arrived, the massive parking lot and causeway (built where the tombolo used to be) filled with cars, camper-vans and buses. The causeway completely cuts off the natural currents and sediment movement of the inner bay, but it is by no means the only manmade disruption. In the 1850s, the channels of the Rivers Sée and Sélune were eroding the agricultural area south of where they entered the bay, and a dike (“digue”) was constructed to force their flow further north; over the following decade, the channel of the River Couesnon was completely controlled and “canalised” all the way out beyond Mont-Saint-Michel itself (the artificial banks for much of this were eroded or overwhelmed by sand by the 1960s). Critically, in 1969, a dam was built across the Cuesnon that effectively ended the power of the river to flush sediment out into the bay. The result of all these interventions was increased natural and manmade growth of the “polders,” the salt marshes that invade the bay and provide valuable agricultural land, together with accelerated sedimentation around the Mount itself. In modern times, the foundations of Mont-Saint-Michel were buried under two meters of sand that had built up since the nineteenth century - the entire sedimentological system of the inner bay was changed – dramatically illustrated in the two maps below showing the locations and changes to the river channels before and after these “management” initiatives.

 

The project to restore as far as possible the nature of the bay has been comprehensive, evaluating hydrology and sedimentology, environmental factors, and the influence on tourism. It is is superbly described at http://www.projetmontsaintmichel.fr/en/, much of the site available in English. The sedimentology modelling alone was a four-year study, a key part of which was the construction of a huge physical model capable of reproducing and predicting sand dynamics (see photos below). The model covers 900 square meters (almost 10,000 square feet) and was used to model 45 years of annual cycles in the bay without further intervention and with a range of restoration options (see my earlier post for a natural version of such a laboratory and references to other such modelling projects).

Over a recent period of forty years, 27 million cubic meters of sediment have been added to the bay and a thousand hectares (four square miles) of new vegetated land encroached into it. The model demonstrated that, by 2042, the marine environment of the inner bay around the Mount would vanish completely. Nothing can stop this happening eventually, but it can be slowed down. There are two keys to delaying the inevitable: remove the causeway and restore the hydraulic power of the Couesnon river to flush sediment out of the inner bay. The projects to accomplish both of these, together with all the associated works, were commenced in 2006 and are due to be completed by 2015. The causeway will be replaced by a simple access structure raised above the sea floor to permit natural flow and sediment movement, and well away from the mouth of the Couesnon. The gigantic parking lot will be demolished, to be naturally replaced by 15 hectares of sand. The access to the Mount will be severed under the highest spring tides of the year, restoring the symbolic isolation of Mont-Saint-Michel.

On the river itself, a barrage has been constructed that will allow the waters of each high tide to be stored behind it and then released, flushing sediment out into the bay – the hydraulic power of the river will be restored, even enhanced. The barrage, shown under construction below, has just been commissioned. The river below the barrage will also be dredged; the product of the dredging, 1.25 million cubic meters of salty sand full of shell fragments that is locally known as “tangue” will be used, as it has been for centuries, for local agriculture and polder maintenance. Importantly, the modelling demonstrated the importance of the river draining in two channels out into the bay, so a structure to split the flow downstream from the barrage opening will be constructed.

The effects of the project will be gradual, but in thirty years or so it is anticipated that the mean level of the sea bed around Mont-Saint-Michel will be 70 centimeters lower than today, millions of cubic meters of sediment will have been removed (much of it quite quickly), and the sea will have recaptured 50 hectares of today’s land. The scene today, below left, will have evolved into something like the view on the right. This is an extraordinary and ambitious project, a fascinating experiment in large-scale restoration of the natural landscape.

The site linked above is the source of much of the information and illustrations for this post, and includes a thorough documentation of the sedimentological work, downloadable as a pdf file here; it’s in French, but superbly illustrated. I have copied below a map of the main components of the whole Mont-Saint-Michel project for reference and further detail.

The "Dieu Protège"

In the previous post I cited the joys of serendipity, and they continue. Travelling down the west coast of Brittany, we were attracted to the old fishing harbour of Douanenez and Le Port-Musée there, a boat museum. This is a museum with a difference - not only are there indoor exhibits of everything from coracles to twentieth-century fishing vessels, but outside, in the harbour, is moored an extraordinary collection of boats that have been painstakingly collected and restored, and around which you can wander at will, clambering up and down ladders, trying out the wheelhouses. Serendipity arose when I discovered that, among these boats is Le Dieu Protège, a gabare sablière - a sand transport.

To the north of Douanenez is Brest, a major port for centuries and the focus of extreme conflict during the Second World War. Used as one of the extensive U-Boat bases and a harbour for German battleships, including the Scharnhorst and the Gneisenau, Brest was the target of constant allied bombing raids. In 1944 the battle for its liberation was vicious, and by the end of the war literally only a handful of buildings remained standing in the city, including significant sections of the mediaeval harbour fortifications. The images below show Brest harbour before and after the war.

The post-war reconstruction of Brest took years and required huge volumes of concrete that, in turn, demanded huge volumes of sand. Le Dieu Protège ("God Protects") was built in 1951 specifically to excavate, transport, and deliver sand for the rebuilding of the city - the sand trade was thriving. It seems that the first owner had proposed various names to the authorities, all of them refused because of other boats already claiming them. He came up with the name in memory of a small boat sunk in the treacherous coastal waters after delivering the church bell to the island of Ouissant (presumably the protection extended only to the bell....). The boat is 23 meters long, has a capacity of 150 tons of sand, and has double wooden hulls to protect against the abrasive effects of its cargo and the stresses of large volumes of sand being dropped into its hold. It was equipped with sails (below, right), but was motorised and was fitted with a substantial mechanical bucket grab (named in French, le crapaud - the toad).

Until this innovation, sand extraction had taken place by beaching the boat and loading the cargo by hand and shovel, assisted, if on the beach, by horses, as shown in the delightful model at the museum (above, left). The bucket could hold 70 cubic meters of sand at a time, and around two hundred bucketsful of sand needed to be hauled up to fill the hold. [Although quoted from the museum documentation, the bucket capacity seems excessive and the numbers are inconsistent - see comment below]. The remaining requirement was a water pump to remove the 15 tons of water that drained out of every cargo. Four anchors would secure her to an offshore sandbank while she worked.

Le Dieu Protège's working life continued for thirty-five years - her last job was dredging the local harbours. She was purchased by the museum in1990 and restored - and, as the photo below shows, she is being further restored today.

 

Go down the steep ladder to the hold today (now empty of sand), and there are fascinating movies being shown of the sablière at work in her heyday. I have taken the liberty of extracting a few still images from these:

 

My thanks to a superb museum - http://www.port-musee.org. There's much, much more to see than Le Dieu Protège, so, if you're in Brittany, take time for a visit.

And I'll leave you with a picture of le sablier at the helm of a gabare sablière  - it's a great place for kids.