Through The Sandglass

Manchester Science Festival

Next monday, the 26th, I'll be giving a talk at the Manchester Science Festival (Manchester UK, that is). A year or so ago, on British TV, there was a series of programmes with titles such as "Ten things you didn't know about volcanoes," "Ten things you didn't know about earthquakes," and so on. It seemed to me that not only were these titles rather patronising to the viewer, but that the programmes, although entertaining, failed to convey the excitement of science. After all, what keeps scientists enthusiastic, and what keeps science going, is what WE don't know. And there's an awful lot in that category.

So I decided to talk about how even an apparently humble material has its mysteries, and illustrates a variety of areas of scientific enquiry. The talk is, of course, intended to entertain, and so I'll be stirring the occasional frivolity and magic trick into the mix, but think about it: granular physics, coastal and desert dynamics, meanders, meiofauna, Mars, Titan...... My challenge (as always) is what to leave out. The talk will be at Blackwells bookshop, 6.30 pm. And Jan Zalasiewicz, whose provocative book, The Earth After Us I've written about earlier, will be talking on tuesday evening. 

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.

A different kind of sand - on the road again in the volcanoes of the Auvergne

I've just spent several days rambling around the geology of the Puy de Dome and the surrounding volcanoes in the Auvergne region of France's Massif Central. These are extraordinary and surprising landscapes - volcanicity with a long history extending up to a mere five thousand years ago, leaving one to wonder whether or not it is indeed all over and done with. But this is not the only fascination of this area; it is one of the less-heralded, but nevertheless key, cradles of geology in the early part of the nineteenth century. Much more on this later, but meanwhile an example of volcanic ash - a different kind of sand - and a sample of the volcanic crater landscape. 

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.

 

Nature's patterns, fractal landscapes, and a beach laboratory

The termination of the seemingly endless stretch of beach and dunes that forms the Atlantic boundary of the Bordeaux region is Cap Ferret, a constantly changing and migrating spit of sand. This guards the entrance to the Bay of Arcachon, a sweeping tidal expanse of sand and mud, and a source of excellent oysters.

My arrival at Cap Ferret was serendipitous in two ways: it stopped raining and the tide was well on the way out (a condition referred to ominously in French as le reflux). I walked past diverse attempts to stabilise the dunes, and warning signs on the risks of "collapsing" and dangerous beaches in the no-access area towards the end of the cape (with suitable polite apologies for the inconvenience), and came upon an extraordinary sight.  

The massive and relentless movement of sand around the cape was reflected in a miniature landscape of shifting designs left behind by the tide and actively sculpted by the water draining down the beach.

A complex pattern of larger sand waves contained within it ripples, valleys, canyons, meanders, deltas, braided channels, point bars, channel bars - lilliputian river systems, actively eroding, transporting, and carving their topography before my eyes. The sand contained a significant proportion of dark minerals, heavier than the quartz grains, which, like the granular segregation of placer deposits, etched out the details and designs of these landscapes. Natural processes operating without heed to scale, features a meter across that could be images from Google Earth - truly fractal designs. I lost track of how many photographs I took - every few steps there was something different and wondrous going on (including the sensation of being sucked into almost quicksand). Endless complexity and beauty: here, just a sampling.

And it struck me that I was in the midst of a vast natural sedimentological laboratory, an ideal and exciting place to examine the complexity and dynamism of natural processes and structures, in the same way that Steve Gough does at Little River Research and Design, or like the model systems at the University of Minnesota's St. Anthony Falls Laboratory. Except that Cap Ferret is much, much, bigger and the landscapes change with every reflux.

Climate change - or not

I was much looking forward to encountering Mont-Saint-Michel, not from the point of view of a pilgrim, or even a namesake, but simply to observe a sedimentary drama that is in the process of being rewritten, restaged, restored. So, on arriving in the delightful town of Avranches (and having, after visiting Utah Beach, admired the prominent memorial in Avranches to General Patton, and the sentiment that lay behind its existence), I ventured to the botanical gardens from where a panoramic view over the bay was promised. What I had forgotten was that, by simply crossing the English Channel, I had not left English weather behind - the word "perturbation" is one of those that is the same in French and English, and, when it comes to the weather, is highly descriptive. Soaked and dripping, I arrived at the viewpoint, which had, in addition to redundant telescopes, one of those very informative panoramic displays whose informative value depends entirely on good visibility. The image above is what I saw, the image below what I was hoping to see. Things did later improve somewhat - the rain paused; I'm not talking of bursts of glorious sunshine but I did dry out a bit. The story will continue .....

On the road - le sablier sur la route

I'm off for a bit of an excursion, wandering, meandering, and otherwise peregrinating through Brittany and then down the Atlantic coast of France - something I've wanted to do for a while. There will therefore be some uncertainty around when and whence the next post. But coasts are fertile environments for arenaceous musings, and who knows what will catch the interest of your faithful blogger. I'll be starting at Mont-Saint-Michel, pictured above, a World Heritage Site that is the focus of an ambitious sedimentological restoration project - so there's grist for my mill already. Then Brittany: ancient geology, strange linguistic heritage, and sandy coves; and my birthday (details withheld) at the westernmost point on mainland France.

 

Turning left, the plan takes in Les Sables d'Olonne (un "côte sauvage" but also a major port where the Vendée Globe round-the-world single-handed yacht race begins and ends) and onwards to the estuary of the Gironde and the bay of Arcachon.

 

The white expanse at the top right of the image above is the Dune of Pyla, the largest in Europe and active. I think I might drop by. And then what? Well, the Gironde runs through a region called Bordeaux - I'll figure out something ......

 

[Mont-Saint-Michel image by Uwe Küchler, GNU Free Documentation License, http://commons.wikimedia.org/wiki/File:Mont_st_michel_aerial.jpg; Dune du Pyla photo from http://kitusai.blog.lemonde.fr/2007/01/21/dune-de-pyla/]