Through The Sandglass

Drawing lines in the sand - the art of Jim Denevan

Anyone who builds a sandcastle, or doodles on the beach, feels the impermanence of such creations. It's one of sand's many qualities - for a material that lends itself to sculpture, writing, and drawing, and for all the toughness of the individual grains, it resists, in conspiracy with waves, rain, and wind, any kind of durability of form. Ripples shape-shift with every tide, dunes move on with every gust of wind - however nature or we may attempt to shape it, these works are ephemeral. There are stories, some perhaps true, many no doubt apocryphal, of Pablo Picasso sketching in the sand on a beach; in one, he is pursued by a woman asking for a small sketch, and he obliges by drawing a picture in the sand.

It is its ephemeral character that gives sand its role in the imagery of passing time - and its uniqueness as a medium. It is that very impermanence that is an intrinsic part of land art of all kinds, but of the work of one extraordinary artist in particular.

Jim Denevan walks out onto a freshly washed Northern California beach, bends down, and draws a circle, the size of a coin, in the sand with his finger. More circles create a spiral nest, the outer ones growing larger. Using a driftwood stick as his paintbrush, he draws bigger circles in the sand, each one nestling with the previous; the design grows fractally. Denevan does all this freehand—there is no outline, no preliminary design; the artwork simply flows from his mind through the choreography of his movement. His work evokes a Japanese karesansui, popularly known as a Zen garden, with its contemplative design of raked sand. Denevan’s design is monumental, ultimately occupying the entire width of the beach. He uses a large rake to highlight the outline and to fill in the spaces with texture. A few hours later, the tide destroys the art and renews the canvas. For Denevan, the transience is part of the art; it recognizes “some kind of truth about life—what is grand, or what is fragile. . . . Everything is transitioning into something else.” Denevan’s designs are diverse, ranging from huge perfect spirals, to representational images, to complex circles and linear shapes, suggesting a more fragile version of the Nazca lines, the gigantic figures in the Peruvian desert—themselves created by the removal of desert stones to expose the light-colored sand beneath.

For Denevan, the process, the dance, the intimacy with the sand is a fundamental component.

He recently made the world's largest freehand drawing, this time on a dry lake bed in the Black Rock Desert of Nevada. It's three miles across and he walked a hundred miles in eight days to complete it. A desert storm washed it away the following week.

Denevan also excels in a completely different form of ephemeral art - he's a renowned chef, creating unique culinary works inspired by local produce and landscapes. Outstanding in the Field is now staging feast tours internationally as well as throughout North America - Jim was incredibly helpful when I was writing my book, and I have an aspiration to coincide with and indulge in one of his events.

But to finish, I'll return to sand, and celebrate the pleasure of its impermanence through Jim Denevan's own words:

One part of drawing in the sand that’s really great is that, no matter what I do, no matter how big it is, I have a completely clean sheet of paper, meaning a completely clean strip of sand that I can return to every day, and there’s an incredible freedom in that kind of artwork.

[see http://www.jimdenevan.com/ and http://www.outstandinginthefield.com/. The Northern California Public broadcasting station, KQED, has a terrific short video of Denevan working and talking about it - http://kqed02.streamguys.us/anon.kqed/spark/jimdenevan.m4v]

Tafoni

Tafoni - the decorations on a festive cake? An ancient grave-robbing cult? The cosmetically enhanced follicles on the head of the Italian Prime Minister? Nope, pits, holes and convoluted caverns in weathered rock.

 

The origin of the term is perhaps lost in the mists of time, perhaps Sicilian (where there are spectacular examples in granite outcrops on the coast), but the phenomenon is an extraordinary example of the diversity of nature's art. Tafoni can be found in many different types of rock and in many different environments (including Antarctica and Mars), but they are very common in sandstones and in the deserts of the world, and so it those that I shall focus on here - particularly since I can use my own photos. There has been a great deal of scientific pondering and analysis on exactly how tafoni are formed, but the general opinion is that the process of salt weathering is the influential sculptor. Water, even in minute amounts, pools on the surface or finds its way in between the rock grains and dries. If the water is carrying salts - minerals dissolved in the water than can include sodium chloride but also a host of other chlorides, sulphates, and carbonates - then they will crystallize out as the water dries. Crystallizing salts increase their volume as they form, which produces significant pressures between the grains, forcing the solid rock to crumble. The chemical and physical solidity of any rock is not uniform and some parts will be more vulnerable than others; the process continues through cycles of wetting and drying, chiseling, excavating, and smoothing. The results can be relatively simple "honeycomb" pits or incredibly ornate sculptures, reminiscent of Gothic cathedrals or the more extravagant works of Antoni Gaudi. The examples here are in Lower Paleozoic sandstones from the Western Desert of extreme southwest Egypt. The "stalks" of the mushroom-shaped rocks illustrate the height of sandblasting by sandstorms (see also my previous entry on 21 January - The man who figured out how deserts work).

 

There is much more that can be said about tafoni, but best to visit Jon Boxerman's comprehensive and entertaining site, http://tafoni.com/Welcome.html and, as always, Andrew Alden, http://geology.about.com/library/bl/images/bltafoni.htm. Or go to Stalking the Wild Tafoni at the Zymoglyphic Museum blog, http://zymoglyphic.blogspot.com/2007/01/stalking-wild-tafoni.html - and once you start browsing around the rest of this wonderful blog, allow some time.

And finally, just to prove that tafoni do not just haunt the deserts of the world, an example from Scotland's Isle of Skye (which, I can assure you, is not an arid place) and, the one photo that isn't mine, San Francisco (courtesy of the National Park Service).

 

[p.s. I'll be away from my laptop for a few days (a blessing and a curse) celebrating my wife's birthday in Barcelona (speaking of Gaudi); I will try to schedule a new post to appear, but have no great faith in this happening - don't go away!]

Magic Crystals - Tales Zircons Tell

The picture on the left is of our oldest earthly possessions. They are sand grains, but special ones, each an individual crystal of zircon, the silicate of the element zirconium. Zircon may be the December birthstone, but these crystals were born 4.4 billion years ago - only a hundred million years or so after the Earth was formed, and are our oldest terrestrial material. They are found in sandstones of the Jack Hills in Western Australia, the tiny grains, less than a millimeter in size, painstakingly extracted one-by-one; the sandstones themselves are only around 3 billion years old, deposited by rivers that carried the debris from the erosion of far older rocks, of which the zircons are the only survivors. And survivors they are: tough as old boots, zircons are essentially indestructible - the original crystal shapes of the Jack Hills grains are still clearly visible - and they survive to tell extraordinary tales. They preserve a record of the ancient chemistry of the earth, and they tell time, the small amounts of radioactive uranium and thorium that they contain decaying constantly to provide a radiometric clock. Formed from the molten maelstrom of the newly-formed Earth, the Jack Hills zircons tell a story of cooling and the formation of solid rocks - and therefore in all likelihood, crust - far earlier than had been previously thought possible. And their chemistry suggests the presence of liquid water, demonstrating that we still have a lot to learn about the childhood of our planet. Looked at closely, using cathodoluminescence and other kinds of clever analysis, zircons commonly show internal zoning, like tree rings or the layers of an onion, recording successive stages in the growth of the crystal, each layer revealing a different chapter in the story of the crystal's growth, and its own age (photo, right - the numbers are millions of years).

Zircons are not major ingredients of igneous, originally molten, rocks, but they are common and they are the toughest, surviving to form constituent grains in sandstones of all ages and from all parts of the world - which makes them invaluable story-tellers, the troubadours of minerals. Look around the geological research that is being published worldwide on any given day, and, where there are biographies of mountain belts to be written, erosional sagas to recounted, or plate movements to be reconstructed, you will find zircons telling their tales. I'll select here just two fascinating pieces of work, tales of two rivers, published in Geology in the last year that illustrate the powers of these magic crystals to reveal extraordinary details of our planet.

The Brahmaputra River is one of the world's mightiest, both in terms of its length and the amount of water and sediment that it carries. It is the third greatest sediment-carrying river, surpassed only by the Yellow River and the Amazon; perhaps a couple of billion tons - the equivalent of eighty million large dump trucks - of sediment pass down the Brahmaputra every year. And where does all this sediment come from? Well, the erosion of the Himalayas, of course. Yes, but exactly where - surely it's not an evenly distributed process? The answer is no, it's not, but it's far more localized than you would think. The river originates in far southwestern Tibet as the Yarlung Zangbo that flows unswervingly eastwards for 1700 kilometers until it takes a very sharp right turn (see the satellite image below) and carves its way across the Himalayas via what is probably the deepest canyon in the world.

 

In the corner of that turn, the "Big Bend," is the region of the mountain of Namche Barwa, a mere 7782 meters high. And that's where the Brahmaputra collects most of its sediment. Researchers from the University of Washington, Lehigh University, and the Australian National University in Canberra (a pleasingly typical international collaboration) have demonstrated the extraordinary rate of erosion in this small areas of the Himalayas - using zircons. Now zircons contain not one, but two clocks. As the uranium decays, the fragments emitted blaze, literally, tiny trails of damage through the crystal, leaving fission tracks that can be quite easily analyzed. These radioactivity "contrails" are highly susceptible to temperature and are only preserved after the mineral has cooled below a certain temperature; this is complex, but for zircons it's around 230 degrees centigrade. For a zircon, crystallized from a molten rock, fission track analysis reveals when the rock cooled beyond this critical temperature, and therefore records the journey of that rock up into the cooler near-surface regions of the earth's crust. Now, we know that Himalayas are still rising as the Indian/Asian plate collision continues, and that rocks that had been deep and hot eventually reach the surface as erosion shovels away the overlying layers. That uplift and cooling sets the fission track age for a zircon crystal. But the region around the Big Bend is rising incredibly rapidly - the zircons in the sands pouring out of the mountains only cooled off 600,000 years ago. This implies that the rocks are being exhumed - carried up to the surface to be exposed to erosion - at rates of up to 20 millimeters every year - which is astonishing. The zircons tell the tale of sediment being supplied to the Brahmaputra at an incredible rate from the small area around Namche Barwa - 50% of the river system's sediment load comes from approximately 2% of its total drainage area. And this is not only a fascinating fact for geologists - as the authors of the paper point out, it has huge implications for flood management and hydroelectric development in the region. 

Now, let's travel north to another of the world's great rivers, the Lena of Siberia. The Lena rises, unexpectedly, only a few kilometers west of Lake Baikal (see map below) and, rather than having anything to do with the lake and its drainage system, sets off northeastwards on its own journey towards the Verkhoyansk Mountains.

 

However, it doesn't cross them but turns left and heads up to the Arctic Ocean into which it deposits a magnificent delta. The Lena's journey covers around 4400 kilometers (it's the tenth longest in the world) and it drains a total area four times the size of Texas. Now I suppose that it's no real surprise that a river will sometimes turn when it encounters a mountain range, but the surprise here is when and exactly why this happened. Again a pleasing collaboration of researchers, this time from the Russian Academy of Sciences, West Virginia University, Stanford University and the University of Arizona, have read the stories that zircons tell about the Lena, a very old river. Three hundred and fifty million years ago, where the Verkhoyansk Mountains are today was the northeastern edge of the old Siberian continent, and rivers flowed to the sea (red arrows), depositing - and depositing and depositing - huge thicknesses of sediment along the continental edge. And then, over the northeastern horizon, appeared another continental fragment, being driven inexorably into Siberia. The great collision occurred, welding together eastern Russia as we now know it, bulldozing up the pile of sediment, and raising the Verkhoyansk Mountains. The bulldozed pile of sand, deposited over a period of 200 million years, is up to 15 kilometers thick - and contains plenty of zircons that record the erosion of the old Central Asian highlands to the southwest. The zircon records show that the rivers, including the ancestor of the Lena, harvested an unchanging selection of eroding rocks from those highlands for that 200 million year period. The Lena changed its course 150 million years ago because it encountered the growing mountainous terrain of a plate collision. Of course today's Lena is the descendant of its ancestral river system and has changed its precise location and itinerary - but the zircons show that it is the latest member of a family of rivers that lasted for 200 million years and, in its upper reaches, for the last 350 million years. As the paper states, "Thus, the life span of major transcontinental drainage systems can be comparable to that of the plate boundaries that surround them." Tiny crystals telling huge stories.

[R.J.Stewart et al., Brahmaputra sediment flux dominated by highly localized rapid erosion from the easternmost Himalaya, Geology 2008;36;711-714; A.V. Prokopiev et al., The paleo-Lena River -- 200 m.y. of transcontinental zircon transport in Siberia, Geology 2008;36;699-702. For accounts of the Jack Hills zircons, see http://www.geology.wisc.edu/zircon/Valley2005SciAm.pdf, http://www.geology.wisc.edu/zircon/Cavosie2004.PR.pdf, (source of the zoned zircon image)and http://serc.carleton.edu/NAGTWorkshops/earlyearth/teaching_refs.html (source of the photos of zircon grains, Aaron Cavosie, Image credit: Aaron Cavosie, University of Puerto Rico, Mayaguez). Satellite image http://visibleearth.nasa.gov/view_rec.php?id=2680. For the immensely complex and fascinating topic of sediment flux, Brian, at Clastic Detritus, has a provocative post at http://clasticdetritus.com/category/sediment-flux/]

 

Costa Bravado - and a paradox

 The photo on the left is typical of those used by tourist boards to lure visitors to sun-drenched beaches, to escape to tranquility and commune with nature, feel the warm sand between the toes - "book now, before anyone else arrives!" The image is part of an advertising campaign to do the job for the Costa Brava on Spain's Mediterranean coast. But, as revealed in the press last week, it's not a picture of the Costa Brava, but rather - the Bahamas! On reflection, this is something that any self-respecting arenophile could have spotted - the sand is white, typical of a tropical beach of largely biogenic materials, fragments of coral, shells, and so on; the sands of the Costa Brava are, to put it bluntly, the usual sort of nondescript brown. The Girona tourist board even resorted to digital alteration of the image to dull the dazzling sands of the Bahamas, but it didn't work too well. Having headlined the advertising with the remarkably appropriate question, "Where does the Costa Brava start?," the board was unrepentant. "What we were looking for was the concept," their director was quoted as saying, and claimed a lack of good quality images of their own beaches,  "There was no intention to lie, nor to betray, nor to think that the Bahamas are better than the Costa Brava and pass off an image of the Bahamas as one of here." Really? They could, after all, have used the real picture of a Costa Brava beach (right).

And then there might be the problem that, if you find an empty Costa Brava beach, it's empty of sand as well. Frenzied coastal development, dams and excessive water withdrawal (reducing sediment delivery to the coast), and random attempts at "coastal management" have all seriously busted the sediment budget - far more sand departs than arrives. After the winter storm season, many beaches are more rock than sand, and immense efforts are put into beach "replenishment."  Which raises the interesting question, important for philosophers and tourist agencies: when is a beach not a beach? After all, an expanse of shoreline rock within which lies a single grain of sand is clearly not a beach - so when does a not-beach  become a beach? This is what is known, at philosophers' cocktail parties, as the sorites paradox, a problem originated by Eubilides of Miletus in the fourth century b.c. Eubilides loved paradoxes (the classic “liar’s paradox” was his), and perhaps he loved the beach, or at least playing with sand. For he became concerned about what is, and what is not, a “heap” (sorites derives from the Greek for “heap”). If a single grain of sand is removed from a heap, it clearly remains a heap, as it does after the removal of the next grain. So, asked Eubilides, when does it become a non-heap? The reverse is the same problem—a single sand grain is obviously not a heap, but when does a non-heap become a heap? The problem, philosophically, is one of vagueness and the imprecision of word usage. So when does a beach become a non-beach, and vice-versa? Answers please on a digital postcard, below.

[images from the Guardian, 11 February 2009, Albert Gea/Reuters and Dorgie Productions/Getty]

Darwin on geology - and sand

The posts this week have been celebrating Charles Darwin as a geologist and have therefore been a slight excursion from the underlying theme of this blog. But, inevitably, Darwin draws me back to my topic. Of course, in the course of his travels with the Beagle, he encountered and described sand bars, dunes, spits, hillocks, plains, and beaches, but among the large and eternally absorbing collections of his writing, I found, to my delight, items which link directly to subjects of my earlier posts - antlions and geowriting - and one that will, undoubtedly, be the subject of a later piece - booming and chirping sands. First, geowriting. I had sought ideas on geologists who write entertainingly on their subject, who convey some of the passion of the science - and Darwin was arguably one of those. The man was an enthusiast, filled with constant curiosity which fired a desire to ask the right questions and discover the right answers:

There is nothing like geology; the pleasure of the first days partridge shooting or first days hunting cannot be compared to finding a fine group of fossil bones, which tell their story of former times with almost a living tongue.

His ideas on the development of the Andes were radical, but well-founded on observation, documented in a delightful and compellingly readable way. Read - and enjoy - the following, from a letter to his sister, Susan in 1835:

I returned a week ago from my excursion across the Andes to Mendoza. Since leaving England I have never made so successful a journey: it has however been very expensive: I am sure my Father would not regret it, if he could know how deeply I have enjoyed it.— it was something more than enjoyment: I cannot express the delight, which I felt at such a famous winding up of all my geology in S.— America.— I literally could hardly sleep at nights for thinking over my days work.— The scenery was so new & so majestic: every thing at an elevation of 12000 ft. bears so different an aspect, from that in a lower country.— I have seen many views more beautiful but none with so strongly marked a character. To a geologist also there are such manifest proofs of excessive violence, the strata of the highest pinnacles are tossed about like the crust of a broken pie. I crossed by the Portillo pass, which at this time of year is apt to be dangerous, so could not afford to delay there; after staying a day in the stupid town of Mendoza I began my return by Uspallata, which I did very leisurely.— My whole trip only took up 22 days.— I travelled with, for me, uncommon comfort, as I carried a bed!: my party consisted of two Peons & 10 mules, two of which were with baggage or rather food, in case of being snowed up.— Every thing however favoured me, not even a speck of this years Snow had fallen on the road.—

I do not suppose, any of you can be much interested in Geological details, but I will just mention my principal, results: beside understanding to a certain extent, the description & manner of the force, which has elevated this great line of mountains, I can clearly demonstrate, that one part of the double line is of a age long posterior to the other. In the more ancient line, which is the true chain of the Andes.—I can describe the sort & order of the rocks which compose it. These are chiefly remarkable by containing a bed of Gypsum nearly 2000 ft thick: a quantity of this substance I should think unparalleled in the world. What is of much greater consequence, I have procured fossil shells (from an elevation of 12000 ft) I think an examination of these will give an approximate age to these mountains as compared to the Strata of Europe: In the other line of the Cordilleras there is a strong presumption (in my own mind conviction) that the enormous mass of mountains, the peaks of which rise to 13 & 14000 ft are so very modern as to be contemporaneous with the plains of Patagonia (or about with upper strata of Isle of Wight): If this result shall be considered as proved it is a very important fact in the theory of the formation of the world.— Because if such wonderful changes have taken place so recently in the crust of the globe, there can be no reason for supposing former epochs of excessive violence.— These modern strata are very remarkable by being threaded with metallic veins of Silver, Gold, Copper &c: hitherto, these have been considered as appertaining to older formations. In these same beds (& close to a Gold mine) I found a clump of petrified trees, standing upright, with the layers of fine Sandstone deposited round them, bearing the impression of their bark. These trees are covered by other Sandstones & streams of Lava to the thickness of several thousand feet. These rocks have been deposited beneath water, yet it is clear the spot where the trees grew, must once have been above the level of the sea, so that it is certain the land must have been depressed by at least as many thousand feet, as the superincumbent subaqueous deposits are thick.— But I am afraid you will tell me, I am prosy with my geological descriptions & theories.

The image at the head of this post is from his cross-section of the Andes constructed after this trip. Elsewhere in Chile, Darwin encountered tales of that extraordinary phenomenon that is found in arid regions the world over - sands that make noises. The repertoire is hugely varied and the science controversial, but "dune tunes" ("the sand of music") are certainly bizarre:

We gladly travelled down the valley to our former night's lodging, and thence to near the Agua amarga. On July 1st we reached the valley of Copiapô. The smell of the fresh clover was quite delightful, after the scentless air of the dry sterile Despoblado. Whilst staying in the town I heard an account from several of the inhabitants, of a hill in the neighbourhood which they called "El Bramador,"—the roarer or bellower. I did not at the time pay sufficient attention to the account; but, as far as I understood, the hill was covered by sand, and the noise was produced only when people, by ascending it, put the sand in motion. The same circumstances are described in detail on the authority of Seetzen and Ehrenberg, as the cause of the sounds which have been heard by many travellers on Mount Sinai near the Red Sea. One person with whom I conversed, had himself heard the noise; he described it as very surprising; and he distinctly stated that, although he could not understand how it was caused, yet it was necessary to set the sand rolling down the acclivity. A horse walking over dry and coarse sand, causes a peculiar chirping noise from the friction of the particles; a circumstance which I several times noticed on the coast of Brazil.

On the return journey, the Beagle paused in New South Wales, and Darwin took time to relax and contemplate:

A little time before this I had been lying on a sunny bank, and was reflecting on the strange character of the animals of this country as compared with the rest of the world. An unbeliever in every thing beyond his own reason might exclaim, "Two distinct Creators must have been at work; their object, however, has been the same, and certainly the end in each case is complete." While thus thinking, I observed the hollow conical pitfall of the lion-ant: first a fly fell down the treacherous slope and immediately disappeared; then came a large but unwary ant; its struggles to escape being very violent, those curious little jets of sand, described by Kirby as being flirted by the insects tail, were promptly directed against the expected victim. But the ant enjoyed a better fate than the fly, and escaped the fatal jaws which lay concealed at the base of the conical hollow. There can be no doubt but that this predacious larva belongs to the same genus with the European kind, though to a different species. Now what would the sceptic say to this? Would any two workmen ever have hit upon so beautiful, so simple, and yet so artificial a contrivance? It cannot be thought so: one Hand has surely worked throughout the universe.

Little had I realized that the humble antlion played a role in the evolution of Darwin's thinking.

And there I will leave Darwin - except for one final comment. Darwin used capital letters in what, today, would be an idiosyncratic fashion. The "one Hand" that Darwin saw working throughout the universe was the hand of natural selection.

[more on the antlion in "From Bogart to Bugs - the Angle of Repose," my 7 February post. For further references on Darwin, see earlier posts in this series, and for a comprehensive look at Charles Darwin, Geologist, see Sandra Herbert's book of that title - http://www.cornellpress.cornell.edu/cup_detail.taf?ti_id=4296]

In high spirits - Darwin on geology (4)

Darwin and Lyell

Today is the 200th anniversary of Darwin's birth. It may have been Sedgwick who gave Darwin his crash course in geology, but it was Charles Lyell who was to become Darwin's close geological companion, mentor, and champion, and so I have selected some choice quotations for a joint celebration. Darwin had taken Lyell's Principles of Geology with him on the Beagle and the two men were to share radical views of how the earth works - together, they revolutionised science and our understanding of our planet - and ourselves.

In 1844, Darwin wrote:

I always feel as if my books came half out of Lyell's brains & that I never acknowledge this sufficiently, nor do I know how I can, without saying so in so many words—for I have always thought that the great merit of the Principles, was that it altered the whole tone of one's mind & therefore that when seeing a thing never seen by Lyell, one yet saw it partially through his eyes

In 1838, Lyell sent Darwin an early copy of his Elements of Geology or the Ancient Changes of the Earth and its Inhabitants as Illustrated by Geological Monuments. Darwin wrote immediately to Lyell:

My dear Lyell

I did not write to you at Norwich for I thought I should have more to say, if I waited a few more days.— Very many thanks for the present of your elements, which I received, (& I believe the very first copy distributed) together with your note.— I have read it through every word & am full of admiration of it.— as I now see no geologist I must talk to you about it. There is no pleasure in reading a book if one cannot have a good talk over it.— I repeat I am full of admiration at it.— it is as clear as daylight,—in fact I felt in many parts some mortification at thinking, how geologists have laboured & struggled at proving what seems, as you have put it, so evidently probable.— I read with much interest your sketch of the secondary deposits.— you have contrived to make it quite “juicy”, as we used to say as children of a good story.— There was also much new to me, & I have to copy out some fifty notes & references. It must do good;—the hereticks against common sense must yield— Phillips will not surely go on saying that the metamorphic schists are disintegrated granite redeposited. By the way do you recollect my telling you, how much I disliked the manner Phillips referred to his other works, as much as to say, “you must, ought & shall buy everything I have written”. To my mind, you have somehow quite avoided this.— your references only seem to say “I cant tell you all in this work, else I would, so you must go to the Principle,” & many a one, I trust, you will send there, & make them like me adorers of the good science of rock-breaking. You see I am in a fit of enthusiasm; & good cause I have to be, when I find, you have made such infinitely more use of my journal than I could have anticipated. I will say no more about the book, for it is all praise.— I must, however, admire the elaborate honesty with which you quote the words of all living & dead geologists.

The two men were to collaborate on the successive editions of Lyell's Principles; the index of my own edition, the ninth, published in 1853, contains nineteen references to "Darwin, Mr. C.", ranging from "on vegetation required for support of large quadrupeds" to "on extinction of animals," via earthquakes, South American drought, "oolitic travertin," and, of course, coral islands. The book contains several pages on the last topic, essentially all describing Darwin's work and quoting him directly. In 1837, Lyell had written to Darwin:

I could think of nothing for days after your lesson on coral reefs, but of the top of submerged continents. It is all true, but do not flatter youself that you will be believed, till you are growing bald, like me, with hard work & vexation at the incredulity in the world.

Lyell would be one of the great supporters of The Origin of Species, defending Darwin and incorporating natural selection into later editions of his books. In November 1859, Darwin wrote to his old friend:

My dear Lyell

You seem to have worked admirably on species-question: there could not have been better plan than reading up on opposed side. I rejoice profoundly that you intend admitting doctrine of modification in your new Edition.Nothing, I am convinced, could be more important for its success. I honour you most sincerely:—to have maintained, in the position of a master, one side of a question for 30 years & then deliberately give it up, is a fact, to which I much doubt whether the records of science offer a parallel. For myself, also, I rejoice profoundly; for thinking of the many cases of men pursuing an illusion for years, often & often a cold shudder has run through me & I have asked myself whether I may not have devoted my life to a phantasy. Now I look at it as morally impossible that investigators of truth like you & Hooker can be wholly wrong; & therefore I feel that I may rest in peace.

Thank you for criticisms, which, if there be 2^d. Edit. I will attend to.I have been thinking that if I am much execrated as atheist &c, whether the admission of doctrine of natural Selection could injure your Works; but I hope & think not; for as far as I can remember the virulence of bigotry is expended on first offender, & those who adopt his views are only pitied, as deluded, by the wise & cheerful bigots.

I won't comment on the continuing resonance of those words 150 years later. Rather, I shall end with a quotation which some readers may find amusing, others perhaps not, but it illustrates the human side of the two men. In January 1839, Charles wrote to Emma Wedgwood shortly before their wedding:

.....it will give you hopes, that I shall gradually grow less of a brute, it is that during the five years of my voyage (& indeed I may add these two last) which from the active manner in which they have been passed, may be said to be the commencement of my real life, the whole of my pleasure was derived, from what passed in my mind, whilst admiring views by myself, travelling across the wild desserts or glorious forests, or pacing the deck of the poor little Beagle at night.Excuse this much egotism,I give it you, because, I think you will humanize me, & soon teach me there is greater happiness, than building theories, & accumulating facts in silence & solitude.

.....The Lyells called on me to day after church; as Lyell was so full of Geology, he was obliged to disgorge, & I dine there on Tuesday, for an especial conference. I was quite ashamed of myself to day; for we talked for half an hour, unsophisticated geology, with poor Mrs Lyell sitting by, a monument of patience. I want [lack] practice in illtreating the female sex.I did not observe Lyell had any compunction: I hope to harden my conscience in time: few husbands seem to find it difficult to effect this.

In high spirits - Darwin on geology (3)

Darwin and Sedgwick

 

It's well-known that, in 1831, Adam Sedgwick, Professor of Geology at Cambridge, President of the Geological Society and one of the great figures of "the heroic age of geology," took Charles Darwin on a short, but highly educational and influential, geological fieldtrip in Wales. Darwin received his invitation to join the Beagle expedition immediately afterwards, and so Sedgwick set the foundations for Darwin's geologizing. It was John Stevens Henslow, Professor of Mineralogy and Botany at Cambridge and a lifelong friend of Darwin who arranged the trip, and it was to Henslow that Darwin wrote from Rio de Janeiro in 1832:

Tell Prof: Sedgwick he does not know how much I am indebted to him for the Welch expedition.— it has given me an interest in geology, which I would not give up for any consideration.— I do not think I ever spent a more delightful three weeks, than in pounding the NW mountains.

The circumstances of the "Welch expedition" are puzzling in many ways. While he had been interested in mineralogy as a child, Darwin was turned off geology while at Edinburgh, having found the lectures "incredibly dull" and the science questionable; it seems that he did not attend Sedgwick's lectures while an undergraduate at Cambridge. Sedgwick was a strong character and a man of outspoken opinions, many of which would not have resonated with the young Charles Darwin. The detailed discussion of the expedition by Paul Barrett makes fascinating reading (see reference below).

Darwin and Sedgwick did not subsequently correspond at any length, but their letters were cordial - until the publication of The Origin of Species. On the 24th November, 1859, Sedgwick wrote a letter to Darwin that, in spite of being signed "your true-hearted old friend," was extremely blunt:

If I did not think you a good tempered & truth loving man I should not tell you that, (spite of the great knowledge; store of facts; capital views of the corelations of the various parts of organic nature; admirable hints about the diffusions, thro' wide regions, of nearly related organic beings; &c &c) I have read your book with more pain than pleasure. Parts of it I admired greatly; parts I laughed at till my sides were almost sore; other parts I read with absolute sorrow; because I think them utterly false & grievously mischievous

............. I have written in a hurry & in a spirit of brotherly love. Therefore forgive any sentence you happen to dislike; & believe me, spite of our disagreement in some points of the deepest moral interest, your true-hearted old friend  A. Sedgwick.

On the 26th November, Darwin replied:

My dear Prof. Sedgwick

I did not at all expect that you would have written to me.— You could not possibly have paid me a more honourable compliment than in expressing freely your strong disapprobation of my Book.— I fully expected it. I can only say that I have worked like a slave on the subject for above 20 years & am not conscious that bad motives have influenced the conclusions at which I have arrived. I grieve to have shocked a man whom I sincerely honour. But I do not think you would wish anyone to conceal the results at which he has arrived after he has worked, according to the best ability which may be in him. I do not think my book will be mischievous; for there are so many workers that, if I be wrong I shall soon be annihilated; & surely you will agree that truth can be known only by rising victorious from every attack.

I daresay I may have written too confidently from feeling so confident of the truth of my main doctrine. I have made already a few converts of good & tried naturalists & oddly enough two of them compliment me on my cautious mode of expression! This will make you laugh. My notion of young men being best judges of new doctrines was not invented for occasion; for however erroneous, I remember nearly twenty years ago laughing with Lyell over the idea.— I have tried to be honest in giving all the many & grave difficulties which occurred to me, or I met in published works. I cannot think a false theory would explain so many classes of facts, as the theory seems to me to do. But magna est veritas & thank God, prevalebit.

Forgive me for scribbling at such length, & let me say again how I grieved I am to have encountered your severe disapprobation & ridicule. Your kind & noble heart shows itself throughout your letter. I thank you for writing, & remain with sincere respect | Yours truly obliged 

Charles Darwin

Joseph Dalton Hooker was a leading botanist and palaeobotanist who worked on Darwin's collection after the Beagle voyage and played a leading role in supporting the development and the publication of The Origin of Species; he was probably the first high-profile scientific figure to publicly support Darwin's theory, and shared the abuse. In 1860, after leading traditional botanists had attacked Hooker, Darwin wrote to his old friend:

How paltry it is in such men as Balfour, Arnott & Co. not reading your Essay. It is incredibly paltry.— They may all attack me to their hearts' content. I am got case-hardened. As for the old fogies in Cambridge it really signifies nothing. I look at their attacks, as a proof that our work is worth the doing. It makes me resolve to buckle on my armour.— I see plainly that it will be a long uphill fight.— But think of Lyell's progress with geology.— One thing I see most plainly that without Lyell, yours, Huxley & Carpenter's aid my book would have been a mere flash in the pan.— But if we all stick to it, we shall surely gain the day. And I now see that the battle is worth fighting. I deeply hope that you think so.

Among "the old fogies in Cambridge" was Adam Sedgwick.

[Barrett, Paul H. 1974. The Sedgwick-Darwin geologic tour of North Wales. Proceedings of the American Philosophical Society 118, No. 2. (19 April): 146-164. Available online at http://darwin-online.org.uk/pdf/1974_Wales_F1964.pdf; The Sedgwick Museum in Cambridge will be hosting a major exhibition, Darwin the Geologist, this summer - http://www.sedgwickmuseum.org/ and http://www.darwin2009.cam.ac.uk/.]

In high spirits - Darwin on geology (2)

William Darwin Fox was Charles Darwin's second cousin, a keen entomologist (he was particularly fond of beetles) with whom Charles had a close relationship throughout his life. From the many letters Charles wrote to Fox while on the Beagle voyage come the following:

From near Rio de Janeiro, May 1832

I am entirely occupied with land animals, as the beach is only sand; Spiders & the adjoining tribes have perhaps given me from their novelty the most pleasure.— I think I have already taken several new genera.— But Geology carries the day; it is like the pleasure of gambling, speculating on first arriving what the rocks may be; I often mentally cry out 3 to one Tertiary against primitive; but the latter have hitherto won all the bets.

 And from Lima, August 1835

I look forward to the Galapagos, with more interest than any other part of the voyage.— They abound with active Volcanoes & I should hope contain Tertiary strata.— I am glad to hear you have some thoughts of beginning geology.— I hope you will, there is so much larger a field for thought, than in the other branches of Nat: History.— I am become a zealous disciple of M^r Lyells views, as known in his admirable book.— Geologizing in S. America, I am tempted to carry parts to a greater extent, even than he does. Geology is a capital science to begin, as it requires nothing but a little reading, thinking & hammering.— I have a considerable body of notes together; but it is a constant subject of perplexity to me, whether they are of sufficient value, for all the time I have spent about them, or whether animals would not have been of more certain value.—

In high spirits - Darwin on geology (1)

This, as can have escaped hardly anyone's awareness, is the week of celebrating the birth of Charles Darwin, 200 years ago. I do not pretend to be any kind of Darwinian expert, and there is much being written elsewhere during this festival, so I shall not burden cyberspace with my own ramblings. Far better, I thought, to let the man speak for himself - as a geologist. For a geologist he was, and an enthusiastic one at that, throughout his life - as an old friend and Darwin devotee in the States wrote to me recently, "I have no doubt that his thinking was fundamentally influenced as much by his geological investigations as it was by Malthusian principles." Darwin's correspondence is now, awe-inspiringly, available online, 14,500 letters, searchable, annotated, and cross-referenced. It is completely engrossing, and I have been spending some time listening to him write about geology. Over the course of the next few days I will simply post some of my favourite extracts.

Written from Mauritius in 1836 to his sister, Caroline:

I am in high spirits about my geology.—& even aspire to the hope that, my observations will be considered of some utility by real geologists.

And, again to Caroline, impecuniously from Montevideo in 1833:

And here comes the whole purport of my letter, to announce more extravagance.— I have really now been struggling for a whole week, but there is a very interesting geological formation on the coast of the Uruguay, & every day I hear of more facts respecting it.— When I think I never shall be in this country again, I cannot bear to miss seeing one of the most curious pieces of Geology.— I wish any of you could enter into my feelings of excessive pleasure, which Geology gives, as soon as one partly understands the nature of a country.— I have drawn a bill for 50£.— I well know, that considering my outfit I have spent this year far more than I ought to do.— I should be very glad if my Father would make a real account against me, as he often says jokingly.— I hope he will not think I say this impertinently: The sort of interest I take in this voyage, is so different a feeling to any thing I ever knew before, that, as in this present instance I have made arrangements for starting, all the time knowing I have no business to do it.

[the Darwin correspondence is at http://www.darwinproject.ac.uk/index.php; see also http://darwin-online.org.uk/acknowledgements.html; Ian Stimpson's blog has a post on Darwin the Geologist, with links to the Darwin geological papers made openly available by The Geological Society: http://hypocentre.wordpress.com/2009/02/04/darwin-the-geologist/; Pools and Riffles has a link through to Darwin's geological cross-sections of South America: http://poolsandriffles.blogspot.com/2009/02/map-monday-10-darwins-south-america.html]

From Bogart to Bugs - the Angle of Repose

I try to make a point of watching all movies that feature sand in a significant role (probably the subject of a future post), and my 88-year-old father-in-law who lives in Philadelphia recently told me of one that I'd missed - Humphrey Bogart's Sahara. "Watch out for the great lesson in the angle of repose," he told me (he's an engineer). And he was right. The movie was made in 1943 and, while Bogart, of course, accomplishes amazing and rather unrealistic feats of survival and military strategy (it was, after all, a wartime release), it features some remarkable scenes of sediment movement. It was filmed in what is now the Anza-Borrego State Park and the dunes beside the Salton Sea, the area that was then the army's California Desert Training Center. In the scene that my father-in-law was referring to, a lone and desperate soldier attempts in vain to climb the steep face of a dune, the sand cascading, sliding, and avalanching constantly around him - just before, miraculously, a British patrol arrives out of, literally, nowhere.

So there I was, back in the strange world of granular materials and piles of sand, any one of which has its own natural angle of repose - the maximum slope at which the grains are stable. Steepen or undermine the slope and grains will tumble down the flank of the pile, reestablishing the angle of repose. Strictly speaking, there are two key angles for a pile of any particular material: the angle of repose is its slope after avalanching and coming to rest; the angle of stability is the slightly steeper slope that it can adopt as grains are added before avalanching (and there's also the angle of internal friction, reflecting the fact that the angle of repose is governed by the friction between the particles). But we'll stick with the first, simple, definition. The angle can vary enormously, depending on the size of the grains, the range in size, how much moisture there is, and so on. You can demonstrate this easlily in your kitchen (like so many geological phenomena) by making piles of the different granular materials which are easily to hand - normal fine-grained salt makes a much shallower pile than coarse salt crystals. The angle of repose is of interest to physicists and sedimentologists - whether it's the means by which dunes move (see the banner image on this blog), small-scale features on the beach, landslides, or the determining factor in the internal structure of sand ripples and banks - cross bedding - that tells us so much about chapters in the Earth's history.

But it's also important in our daily lives - and not just in the kitchen.

Anywhere that granular materials are stored, whether it be in silos or in piles of aggregates, mining products, or cereals, the angle of repose - and its sensitivity to changing conditions - is something that needs to be carefully managed. Failure of the slope of a sand pile is a regular cause of tragedies on the beach and gold mining in placer deposits, not to mention in the sand mines of Long Island (previous post). The failure to properly manage the gigantic tips of refuse from the coal mines of Wales resulted in the appalling tragedy at Aberfan in 1966, where the collapse of one of those manmade mountains killed 144 people, including 116 children in the buried school.

But on a lighter note, the angle of repose would seem to be something well-understood by various critters, notably the antlion, sometimes referred to as the sand dragon. The antlion is the larval stage of a large family of insects, the  Myrmeleontidae, the adults of which are quite attractive four-winged creatures. But the larval stage - and they can remain larval for several years - are fearsome predators. The 2000 or so species occur around the world, known colloquially in North America as doodlebugs, since their rambling tracks in the sand resemble doodles on paper. Doodlebugs love the angle of repose and use if very effectively in obtaining their dinner. An antlionwill excavate, backwards, a pit in the sand and bury itself at the bottom, its voracious and venom-laden jaws poised for a visitor. The visitor - an ant or any other victim for the undiscriminating antlion - will fall into the pit and struggle in vain to escape against the angle of repose of the sides. Its struggles are further thwarted by the antlion throwing jawfuls of sand at it, precipitating further avalanches, until dinner is served (there's a great video of this drama here)

Oh, and when it's finally ready to move on in its development, the antlion will spin silk from its posterior and use it to glue together a cocoon of sand grains for its pupal stage. 

  

 [antlion and pit images, courtesy of Scott Robinson, pupa image,Jonathan Numer, Creative Commons Licenses; Aberfan image and detailed information from Iain McLean & Martin Johnes, http://www.nuffield.ox.ac.uk/politics/aberfan/home.htm]