Through The Sandglass

Stories in Stone - the Virtual Book Tour continues

 

A virtual conversation with David Williams, author of Stories in Stone: Travels Through Urban Geology

Since Through the Sandglass is one of David’s last stops on his whirlwind virtual book tour, Michael decided that it would make a change to have the questions presented by not by another geologist but by that elusive creature, “the interested general reader,” in this case MW’s wife.

Given that my inclinations are toward the literary rather than the scientific, a natural focus for my questions will be Chapter 3, “Poetry in Stone—Carmel Granite.” I can assure the geoblogosphere, though, that there’s a sturdy underpinning of hard geology, the “bones of the old mother” (Robinson Jeffers, quoted on p. 48), in this chapter, too.

Here goes.

I can see now that Robinson Jeffers could clearly be considered the patron poet of geologists, inspired by granite to create his legacy in both words and stone. Which drew you to him first, his poetry or Tor House and Hawk Tower?

The buildings came first; I have to admit I know little about poetry. My wife and I have regularly visited Carmel to see her grandparents and during one we saw Tor House and Hawk Tower. We later took a tour and I became completely captivated by the structures and how they seem to grow out of the land. My passion for them only grew more as I read Jeffers’ poetry and discovered his brilliance, particularly in his evocation of place. As I wrote, one can learn so much about the plants, animals, and geology of the Carmel region that it is almost as if he has written a field guide. One of my favorite lines of his geologic poetry is “Cataracts of rock/Rain down the mountain from cliff to cliff and torment the stream-bed.” The idea of water tormenting its own stream bed is perfect.

“My fingers had the art to make stone love stone” (Robinson Jeffers, p. 48). Are you familiar with the work of the New England dry stone craftsman (his modest word—I’d say genius) Dan Snow? Hawk Tower and Tor House may be mortared, but their deliberately rough exteriors evoke the elemental quality of Snow’s creations (which, sadly, I’ve only seen via DVD and photographs). He writes, in his book Listening to Stone, “The thinking that goes along with the placement of each stone incrementally adds to what is, ultimately, the wall conceptualized. The stones provoke the thoughts and the thoughts give birth to the form. A finished construction is a thought process petrified. Within a wall are all the moments that created it. They remain there like hidden messages slipped between the stones as they were placed. The finished wall’s character is defined by the spaces between the stones as much as it is by the stones themselves.” Your thoughts on spaces? And on anything else Snow says here as it relates to Jeffers?

I think that what both men show and say is that there is an essence to stone that directs their work. They cannot build or work with rock without considering the textures, colors, and shapes. And because they are working by hand, slowly and considerately, they are able to create an organic whole out of the individual stones they choose.

In regard to spaces, I cannot say anything more eloquent than Snow but I would like to comment on mortar. One aspect of Jeffers’ rock work I like is that you can still see his fingerprints in the mortar, what I called “trace fossils of a man and his passion.” They remind me of seeing the fingerprints in the ancient dwellings of the American Southwest or from a geologic point of view, seeing tracks or storm traces in sediments; they are single moments of time recorded and preserved. To me they are a way of connecting the human time scale and the geologic time scale.

I really like the way you allow other authorities and storytellers to speak in your book. Chapter 3, for example, features two geologists, Aaron Yoshinobu and Dave Barbeau. There must be some interesting back stories to at least a few of the friendships you struck up in the course of writing . . . .

One of the great pleasures of writing this book was my interaction with the experts. So many people went out of their way to help me whether it was driving half way across Italy, opening up a closed quarry, reading chapters, or ferreting out manuscripts.

As I noted in the text, one of the people who went far beyond anything I expected was Ruby Wilde, who grew up in Lamar, Colorado, the home of the petrified wood gas station I write about. I forget how we connected but over a period of several months we exchanged numerous emails and calls. She even drove several hours from her home back to Lamar and spent hours combing through newspapers, talking to old friends, and searching official records. I think she became more obsessed with the station than I did. When she came to Seattle on visit we had a great discussion over beer.

Another person was Bob Thrasher, who had worked the Indiana mills in the 1950s. A great raconteur, he invited me into his home and regaled me with stories of the old days. He was clearly proud of the work he had done.

You mention that friends sent Jeffers rocks from all over the world to use in Carmel and that he returned the favor by taking specimens of his local granite to Ireland “to keep the balance of the world.” Thinking of the minerals and sand samples around our flat, I have to wonder about rocks chez Williams. Could you share some photos of your collection?

Of course, like any good geologist, I have a collection of rocks, most of which I found but a few exotics, such as ones from Antarctica, Africa, and the bottom of the Beaufort Sea, that friends sent. I also acquired rocks for each chapter I worked on. I even have a chunk of Carrara marble that used to be on the Amoco Building. I was always worried when traveling that the rocks would be confiscated at airports, particularly my chunk of Morton Gneiss, which has incredibly sharp edges.

Here are two shots of the rocks on my shelves. There’s rocks from New Zealand (from what became Mt. Doom in Lord of The Rings), Siberia, Mount St. Helens, the Devils’s Hole Pegmatite in Colorado, and Morocco. My wife and I also have a rock walkway and several areas lined with rock we have collected.

I was impressed by your responses to the photographs you were presented with on the Daily Dose of Architecture blog. Comments on Yale’s Beinecke Rare Book and Manuscript Library, please?

Thanks. I had fun answering those questions. The Beinecke is a very cool building. I have been lucky enough to visit it. For those who don’t know, the walls are basically “windows,” but not ones made of glass. Each window is a 1.25-inch-thick marble panel, which allows filtered light to enter the library. This prevents any direct sunlight from hitting the rare books and manuscripts. From a less practical standpoint, the use of marble windows connects the building with the old books it houses; because the light within changes throughout the day, working in the Beinecke sort of feels like working in pre-electrical times, when one relied on natural light. As you hold a book from 1700s, it is easier to put yourself in the position of one reading that book when it was written.

At the end of Chapter 3, you write, “Tor House and Hawk Tower are the only structures [Robinson Jeffers] could have built for the site. How could I not love those buildings?” What other structures (with or without a ghost, “a dark one, deep in the granite” (RJ, p. 67)) have made you feel the same way?

I instantly liked the petrified wood gas station in Lamar. At sunset it looks like a little castle. You can see how each piece was chosen and placed precisely, what Dan Snow calls a petrified thought process. The travertine of the Getty enthralled me [image at the head of this post]. I specifically wrote “travertine of” because it is the stone I liked more than the buildings themselves. Another special building for me was the one in Brooklyn that had been restored with brownstone and not with  stucco. It was true to geologic essence and true to the historic  ways that people used brownstone.

 And finally, since this is after all Through the Sandglass, do you have any observations on matters arenaceous that you’d like to pass on?

Yes, as I wrote in chapter one, this book began with sand, when I “eroded” some from the brownstone base of Harvard Hall on the Harvard campus. As that sand rested in my hand I made the realization that the brownstone I had been seeing in my wanderings in Boston was the same material, a slightly rusted sandstone, that I had been living in and around in southeastern Utah. Brownstone and red rock are two names for the same species of rock. And it was out of this realization that I found stories of natural history that could sustain me in Boston away from the desert I had lived in for the past nine years. These stories provided the seed for my book.

[Many thanks to David and my wife, Carol, for this contribution to what has been a really interesting idea - a virtual book tour. I've already posted some comments on David's engrossing book, but I want to make sure that you visit his blog at http://stories-in-stone.blogspot.com/, where you'll find other reviews and events on the tour. All photos courtesy of David Williams, except for the Dan Snow book cover and the Beinecke Library, the latter from their website]

The mother of all extinctions and the perils of correlation (2)

 

The previous post, instalment one of this saga, looked at what a geologist must do, faced with rock exposures in, say, a cliff face, to read the ledgers of our planet's past. How the sequence of layers records different and changing sedimentary environments, and how these layers must be traced and correlated laterally to build up a picture of what the surface of the earth looked like and how it changed with in time and place. But then we must appreciate that the simple correlation, joining up the pieces of the puzzle by matching rock characteristics (lithostratigraphic correlation) is not the same as a chronostratigraphic scheme because essentially all sedimentary layers are diachronous - the timing of their deposition varies from place to place. But a lithostratigraphic approach is the necessary starting point - unless the geologist is incredibly lucky and finds a real equivalent of my imaginary "pulpite," a layer whose actual age can be determined, the rocks are all he or she has - what you see is what you get.

From time immemorial, it has been the convention that the pile of rock layers is described and depicted as if looking at the cliff face in profile - a column is drawn, showing the different lithologies of the different layers, and reflecting their toughness - rocks resistant to erosion, for example, sandstones, are drawn as ledges, "cliff-formers," while shales, easily eroded away, are less prominent. Here's an example from a study of the 140 million year old Dakota Sandstone in Colorado by workers at the University of Kansas. Sections from different places (I've only included two here for simplicity), annotated with details of the rock type, are put next to each other and the proposed correlation lines drawn between them; in this example, the interpreted environment of deposition of the successive "packages" of sandstones and shales is also included. The correlation lines are drawn with certainty - but note how different the two piles are, only 4.5 kilometers away from each other. Nature abhors continuity, but the geologists can argue for their interpretation from the evidence and the data, and tell a coherent, sensible, geological story - it may not be exactly right but it works. Of course, what the scheme doesn't tell us is when the front of the delta was at what is now Billy Creek and when it was at Chaffee Creek - we must be careful what conclusions we draw.

 

And the conclusions we draw may differ significantly depending on how such correlations are made and what we infer the significance is for timing and diachroneity; a single sandstone layer, perhaps only a few centimeters thick, depending on how it's correlated from place to place, can change the geological story dramatically. And that is exactly where I've been trying to get to with all this pre-ambling.  

The Karoo Basin of South Africa is a spectacular place. Its landscapes are ones that seduce a writer into the old clichés of endless skies and panoramic vistas - because that's the way the place is. The rocks of the Karoo that make these wonderful landscapes are the ledgers of a long period of earth's history; hundreds of millions of years of change are recorded there, including one of the most dire and catastrophic changes that life has endured, the Permian-Triassic extinction. The reasons and details are still unclear and the subject of vigorous and exciting debate, but the fact is, as I wrote in instalment one, that 250 million years ago, 90 percent of marine species and 70 percent of land life were obliterated, they disappeared forever.

As I described in the Alaska river example in the previous post, walk along a river system today and you'll eventually get to the shoreline, the beach and the marine realm beyond. So it was in the Permian period in the Karoo - mountains to the south and west were being worn away, the detritus carried by rivers to the sea, and, in the deep parts of the marine basin, sheets of sand and mud were deposited by the same processes we see, for example, in the Monterey submarine canyon today. Those layers are now preserved in the landscape shown below, which I had the pleasure and privilege of roaming around some time ago. Stratigraphy and correlation is relatively straightforward in these marine sediments - the layers are more or less continuous and can be traced in three dimensions around the terrain. But in detail, even those layers are not continuous - the lithology and the architecture changes laterally.

 

But even with lateral changes and diachroneity, the great advantage of marine deposits is that not much erosion occurs on the sea bed - deposition is the order of the day, and the entries into the ledger are made continuously - the story is a joined-up one. And, within the marine sedimentary pile of the Karoo are beds of volcanic ash that represent geologically instantaneous events - and contain zircon minerals that can be dated radiometrically (see my earlier post on Magic crystals - tales zircons tell). Recent international research collaboration has used these ash layers to pin down exactly where the boundary between the Permian and Triassic periods - the time of the great extinction - is in the sedimentary pile. But travel towards the Permian shoreline and up onto the land where the rivers were flowing, and things become much more complicated. Of course they do - the land surface is dynamic and constantly swept and excavated by those rivers: lateral continuity is abhorred. But that's where the record of life's catastrophic experience is, nevertheless, preserved. It's in those sediments that we see the diversity of vertebrate life on the land decimated. In the sands and muds of the latest Permian is a thriving ecology, dominated by the dynoconodonts, mammal-like reptiles of whom a good example is rambling unsuspectingly around the bottom of the image at the head of these posts - it was as happy as a turkey the day before Christmas. In the sands and muds of the Triassic period, just a little higher up the pile, his place is taken by one of the few survivors, smug lystrosaurus, who would go on with his extended family to found the dinosaur dynasty. Other vertebrates that disappeared at the end of the Permian or only first appeared in the Triassic "recovery" after the extinction tell the detailed story. Even the character of the sediments changes dramatically - the hallmarks of the sands of the late Permian rivers suggest that they were relatively tranquil, meandering across their floodplains, as on the left of the image below. The rivers of the early Triassic were far more violent, braided channels constantly changing course and carrying huge cargoes of sediment (right) - quite possibly because the land was no longer protected from erosion by plant life.

 

In between these clearly Permian and clearly Triassic sediments, things are a mess. But it's a geological mess that should shed light on how the extinction occurred, when it occurred, and how long it took, and these rocks have long been the subjects of devoted scrutiny by teams of researchers from around the world. The image below is taken from a 2003 paper by Greg Retallack of the University of Oregon, Roger Smith, of the South African Museum, and Peter Ward from the University of Washington - leading workers in the field. It summarises neatly and graphically the typical stratigraphy and the extinctions across the Permian-Triassic boundary in the Karoo. 

 

The difficult and controversial part of the sedimentary pile is the section marked "laminites." These layers, sometimes purple, sometimes red, and shown in the image at the top of this post, are thin layers - laminae - of fine sandstone, siltstone and shale that contain no evidence of life whatsoever - they are referred to as the "event" zone or the "dead" zone, the pages of the ledger that record the extinction. The work has built up a picture of this zone being correlatable across long distances in the Karoo, comparable with the stratigraphy of the extinction elsewhere in the world and consistent with the definition of the boundary in the equivalent marine sediments; and it's not just lithostratigraphic correlation - evidence from the well-defined timing of reversals of the earth's magnetic field, the chemical signatures of isotopes in the sediments, and at least one radiometric date, support this. And an important implication is that the extinction took place in what is geologically a very short period of time.

Now, earlier this year, Robert Gastaldo and students from Colby College in Maine, together with Johann Neveling of the South African Council for Geosciences, published a paper suggesting a radical revision, and titled it "The terrestrial Permian-Triassic boundary event bed is a nonevent." Working in part in the same area as Retallack and his colleagues, across the kind of outcrops of the "event zone" shown at left, they identified a single sandstone layer at the top of the laminite zone and correlated it, lithostratigraphically, across a valley to a different level - 10 meters different - than proposed in the earlier work. From their paper, I've reproduced the two different correlations below (slightly simplified and annotated) - the piles of sediment, the lithostratigraphy, from four different locations are the same, but above, A, is Gastaldo's interpretation of the previous correlation, below, B, his proposed revision. This whole issue is far more complex and involves far more detail and data than I have been able to include here. The key point is that the substantial difference hinges on the interpretation of the correlation of the one single thin bed of sandstone - but the implications are huge.

 

In scheme A, the "event zone" is a common and roughly synchronous set of sediments across the Karoo, and the extinction was rapid;  in scheme B, different things were going at different places and times and the extinction took place over a long period of time; and the implications cascade onwards, for what species survived for how long and for how life recovered. But, as Bryan at In Terra Veritas pointed out shortly after the paper was published, it ends up relying on lithostratigraphy and adds no chronostratigraphic data, no time framework. It's for this reason that I have spent so much time trying to set out the pitfalls of lithostratigraphic correlations and the importance of establishing a chronostratigraphic framework - as I have said many times, diachroneity is everywhere and nature abhors continuity.

Now Gastaldo's paper has, as I'm sure was intended by the melodramatic title, stimulated all kinds of attention in the science news press - including the heading "The catastrophe that wasn't" on a highly reputable site. In an article in the June edition of Earth magazine, more soberly titled "Permian extinction layer not actually extinction layer?," Retallack comments that correlations have been misinterpreted:

 The problem, Retallack says, is that Gastaldo incorrectly assumed that he and his colleagues had matched a laminite on the western side [of the valley] composed of fine sandstone with a laminite on the eastern side composed of shale......

Although Retallack and his colleagues disagree with some of Gastaldo's findings, they agree that the laminated interval, or any other geologic feature that occurs at, above or below the P-T boundary, cannot be used on its own to mark the boundary itself. Instead, Retallack says, scientists should use the fossils themselves to mark the extinction and later the recovery, as he and his colleagues have done. Gastaldo's work on the stratigraphy, therefore, "doesn't affect where we place the boundary. It doesn't affect the extinction."...... Peter Ward...... agrees. "It's much ado about nothing," he says.

It may or may not be much ado about nothing, but it is a dramatic illustration of not only the perils of correlation, but the distortion of science. This distortion is precipitated by two factors: first, the provocative title used for a scientific paper, that is a declaration in the interests of publicity, and second, a dispiriting apparent lack of understanding that this is how geology, how science, works. That there is never an absolute truth but rather a process of observation, testing, dispute, and refinement that should lead to an increasingly better understanding - but with multiple working hypotheses and the arguments that accompany them along the way.

And it's very much up to us to broadcast and defend this process, not simply for general scientific appreciation, but because we also add grist to the mill of the "Answers in Genesis" crowd who gleefully reported as follows (excuse me for quoting it verbatim and in total - I couldn't bring myself to summarise it):

The Permian extinction is considered by old-Earthers to have been the largest mass extinction in Earth history, with 90 percent of marine species and 70 percent of land species dying out. It has also long been thought of as a sudden, catastrophic event—until now.
A team led by Colby College paleontologist Robert Gastaldo takes a different view. Gastaldo led students on six trips to South African locations purported to be home to evidence of the Permian extinction—specifically, a thin sedimentary layer separating the Permian period from the Triassic that followed it. But according to Gastaldo, that layer “couldn’t be traced more than about 100 meters laterally,” showing that it wasn’t a global event. “We spent days walking kilometers throughout the [sites] trying to trace it from every angle and couldn’t,” Gastaldo said.
Yet in other places, the team found the sedimentary layer eight meters below the Permian–Triassic boundary! Gastaldo’s conclusion? “Because the boundary event bed doesn’t occur at the same position in the rock record there can be no one, unique event.”
The creation model considers many of the sedimentary layers we observe—including most of the layers that have fossils—to have been laid down by geological events associated with the global Flood (including volcanic activity) along with the Flood itself. It’s therefore very easy to incorporate ideas such as the Permian extinction, or the better-known K–T (Cretaceous–Tertiary) extinction event, with the Flood model. Even if evolutionists decide a certain event took place millions of years earlier or later than what was once thought, that translates in the Flood model to likely mere months (or less) of difference.
We also have to smile whenever longstanding evolutionary ideas are overturned. In this case, a sudden Permian extinction event is now “last year’s fact,” as the CreationWise cartoon says. While a benefit of the scientific method is that hypotheses incorporate new evidence, that’s also the drawback of using science as the be-all and end-all of knowledge.

To anyone who has stuck with me this far, to the bitter end, so to speak, congratulations and heartfelt appreciation. What started off as a little story about a little layer of sand with big stories to tell, ended up as an epic saga - but I hope you'll agree that it's fascinating stuff.

[for news reports on the controversy see http://www.nsf.gov/news/news_summ.jsp?cntn_id=114276&govDel=USNSF_51 and http://www.physorg.com/news155238422.html; Gastaldo's paper can be downloaded from http://www.colby.edu/~ragastal/RAG_reprints/RAG2009a.pdf and examples of the other side of the story can be found at http://www.nasmus.co.za/PALAEO/jbotha/pdfs/Smith%20and%20Botha%202005.pdf, http://www.fsl.orst.edu/wpg/events/S02/RiverMorph.pdf, and http://www.gps.caltech.edu/users/jkirschvink/pdfs/WardKarooScienceFinal.pdf. For several key papers published by the Geological Society of America, and therefore not easily available to non-members, please contact me for PDFs.]

The mother of all extinctions and the perils of correlation (1)

 

Nature abhors a vacuum, continuity and the status quo. Variety is the spice of life and change is the order of the day. Such things make life complex for a geologist, but also exciting and lead to puzzles, multiple working hypotheses, debate, controversy - and progress. This tale is an example of all of this, of how science is a process, not an answer, how big questions can be addressed by small-scale scrutiny, and how thin layers of sand and mud can be testaments to one of the most catastrophic events in life's history. But it's a complicated story to tell - and there's a twist at the end; I've been wrestling with it for some time; now there's nothing for it but to try to tell the tale, so here goes - it'll take a while and will come in two instalments.

We sometimes talk of rock layers being the ledgers of our planet's history, and the geologist's task as being to read those ledgers, to interpret and translate the writing. Stratigraphy, from the Greek for layers and writing, is the branch of geology that attempts to do this job, to set out in three dimensions the sequence of events recorded in different places by piles of rock layers; and really it is the study of four dimensions, since the vertical direction of those layers, assuming they have not been disturbed by the churning of tectonic plates, represents time, successively younger layers piled on older ones. The analogy is often made to a cake - "layer cake stratigraphy" refers to a simple and continuous pile of sedimentary beds; here's a beach sand, then on top of it a dune sand, and, on top of that the muds and shales deposited in a lagoon. It makes for a nice simple story: sea level dropped, the beach migrated following the receding shoreline, dunes migrated over the old beach and lagoons moved over the old dunes. The sediments in the picture at the head of this post (ignore, for the moment, my reptilian Photoshop frolics) show, from a different environment, layer cake stratigraphy, a nice, simple, pile of sand and mud layers. But the width of this outcrop is only a few meters - try to follow a particular layer for any distance to the left or right and chances are things will change, for nature abhors continuity.

A lack of continuity in the stratigraphy can occur for any number of reasons, the most brutal being that erosion has removed everything, a valley has been ripped into the ledger and we must try to find the equivalent pages on the other side. Or tectonic churning has caused a fracture and movement on a fault has displaced our precious cake deep below our feet - we must again try to find the other piece of the cake elsewhere if we are to continue reconstructing its story. Layer cakes are great and to be treasured when they occur, but, more often than not, things are not that simple.

 

Even without erosion or tectonic disruption, nature's dislike of continuity means that a particular layer will change laterally as we follow it along. To illustrate this, imagine that you, suitably equipped, take a stroll across the Alaskan river valley shown below, taking note of the sediments beneath your feet. In doing so, you will encounter the sands, gravels, and muds of river terrace deposits, old flood deposits, sand bars, active river channels, old, abandoned, river channels and point bars, lakes, vegetated soils, and, as you finally clamber up the side of the valley, much older rocks of the hills into which the river is carving its way.

 

This scene is, literally, a snapshot in time of a small part of the earth's surface - it was taken decades ago and the scene would look distinctly different today since a dynamic and powerful river system like this one sweeps back and forth across its valley continuously. There is virtually no continuity of a particular sediment whatsoever - and, if you follow the river to the sea, the sediment will change again to beaches and progressively deeper water marine environments - all representing the single snapshot in time. Now imagine the river scene captured in cross-section in a cliff face a few million years from now - the stratigraphy will show dramatic lateral (and vertical) changes, the possible continuity of individual beds difficult to follow. A thick sandstone bed in one place will become thinner and disappear laterally, or perhaps split into two, thinner, beds. Below (thanks to the Texas Bureau of Economic Geology field seminar site) is just such a cliff, showing 50 million-year-old river sediments in Wyoming. Lateral continuity? No such thing.

 

Now, the key to telling the story of a chunk of the earth's history from outcrops such as this is correlation - taking pieces of the puzzle and putting them together, connecting layers and piles of layers in a way that makes sense, that tells a coherent story (not, for example, one that implies glaciers reaching down onto a tropical beach). Trying to read and correlate the incomplete and discontinuous ledgers is like trying to read an article that has been chopped up. Below is part of one of the articles I shall describe in the next instalment, but I have deleted a narrow column in the middle - the valley - and a couple of lines from the column on the left - sandstone layers that disappear laterally. It's perfectly possible to correlate across the gap, reconstruct the original, and make suggestions for what the missing words might be - but it's not simple and the result is open to different interpretations. Nevertheless, the fact remains that it was a coherent article, telling a joined-up, sensible story. It's worth noting that a single, straightforward, correlation - in this case the paragraph break, is a good place to start, to anchor the puzzle. 

 

In the first instance, the simplest thing to do when faced with the puzzle of correlating two piles of rock layers, is to match the character of individual layers - their lithology. A distinctive sandstone layer that has purple pebbles along its base on one side of a valley can be correlated with a similar sandstone with purple pebbles on the other side. In making this connection, you have perpetrated an act of lithostratigraphy - setting up a stratigraphic scheme simply by describing and using the character of the layers - for sandstones, their grain size and composition, the range of grain size, any features such as ripples, and so on. This works well in putting together a framework of the geological sequence over an area or a region, but what you have not done is to pin down the timing. Look again at the Alaskan River - your stroll took you across a wide variety of sediment types. But let's consider the partially overgrown banks of sand and gravel in the foreground: they may form a roughly continuous layer, but they were deposited at successive stages of the river's migration - they are more or less made up of the same sediments and they are right next to each other, but they don't represent a single time, a single episode of deposition. The sediments of which they are made are, in the jargon of the trade, diachronous - their age varies from place to place. Whether it's because sea level is always rising or falling, or rivers are always wandering around their valleys, or dunes are always on the move, virtually every layer in a sedimentary pile is diachronous to some extent - often dramatically. And so lithostratigraphy tells us nothing about the timing of the story, the evolution of events in the particular part of the earth that we are studying. To rectify this, we must look for clues that allow us to overcome diachroneity, to make correlations of what was going on at the same time, to reconstruct the picture of the Alaskan river landscape - we need a time framework, a chronostratigraphy. To correlate layers that document the things that were going on at the same time, fossils can often be of help. As can any means of measuring the age of a rock directly, through the different methods of radiometric dating, or an ability to calibrate layers against a timescale that we have sorted out in detail, such as the periodic reversals of the earth's magnetic field. But often, as is the case with the rocks of the Wyoming cliffs, these methods are simply not available, there are no fossils, there are no dateable minerals - we simply have to do our best to tell a story that makes geologic sense.

Correlations made on the basis of lithostratigraphy and chronostratigraphy are invariably different. Below, I've sketched a  cartoon of the two sides of a valley. In this case, we've got lucky. High up in the pile is a strange rock that happens to contain newspaper fragments - it's called, lithologically, pulpite (I am, of course, making this up). Lithostratigraphy leads us to correlate the base of this distinctive layer from one side of the valley to the other. But, on examining the newspaper fragments, we find that, on the eastern side they come from 1954, and on the western side, 1963 - the pulpite is diachronous. The chronostratigraphic correlation, the important one, shows that at the time that the pulpite started being deposited in the east, sandstone, let's say with all the characteristics of a river point bar, was being deposited further west. We can now begin to put together the picture of the earth's surface at this location, the paleogeography: a map that shows a pulpite environment of deposition next to a river bank.

 

With every successive detail we look at, with every incremental piece of research, the story becomes clearer, the palaeogeography better-defined, the correlations more precise. But nature's games invariably mean that the puzzle is never complete, questions always linger and avenues for further work become apparent. This often is the basis for vigorous debate between different geologists working on different parts of the same puzzle, and it's what makes the science exciting. What these differing interpretations and vigorous debates don't mean is that the science is wrong, or that significant events identified by earlier work didn't occur - they simply illustrate how science works and how the picture comes more into focus as more data are gathered and fragments of the puzzle fitted into place. 250 million years ago, life on earth suffered the mother of all extinctions - 90 percent of marine species and 70 percent of land life were obliterated. Whole families and genera of creatures disappeared forever. How this took place and why, whether it was geologically sudden or occurred in a series of pulses of mortality, remain questions on which considerable ongoing research is concentrated. But the fact of the extinction is exactly that - a fact. Some of the details of how it happened are contained in the testimony of the layers shown at the top of this post, and the refinement of our understanding of this testimony continues - amid considerable debate. But the vigour of the debate and the vicissitudes of lithostratigraphy versus chronostratigraphy, in no way warrant headlines on credible science news sites such as  “The catastrophe that wasn’t” - that in turn feed the frenzied celebration of the creationists. But more of that next time.

[The outcrop photo at the top of the post is from Earth magazine, June 2009. In terms of the principles of stratigraphy that I have attempted to introduce here, there are many superb sites for details, illustrations, movies, etc. A small selection that will take the interested reader further (in addition to the Bureau of Economic Geology site linked above): http://courses.washington.edu/ess456/; http://strata.geol.sc.edu/index.html; http://courses.washington.edu/ess456/2009files/FaciesIntroWalther.pdf]

Sand, glorious sand: Mars in high-resolution

[Just incredible. If you have a spare hour or so, go to http://hirise.lpl.arizona.edu/ and browse - and then browse some more. Each of the thumbnail images on the site is actually from a satellite pass, and clicking the "RGB color (non-map projected)" link downloads a long narrow image; I've simply compiled segments of some for this "montage." Thousands of geologically and artistically staggering images, all, wonderfully, in the public domain -  Credit: NASA/JPL/University of Arizona. A good way to mark a hundred posts on Through the Sandglass.]

Local ingredients - the sands of the Thames

 

Contrary to the benign atmosphere of the old print, above - kids having fun on a day out - the occupation of mudlarking on the Thames in London during the 18th and 19th centuries was anything but fun - it was appalling. The river and its banks were stinking, fetid, and festering, awash with raw sewage, industrial waste and dead bodies, and the poor souls, as often as not children and old women, whose last resort was to scavenge the sand and mud at low tide, wading in between barges and under wharves, faced disease and death for a penny a day. In 1851, Henry Mahew wrote in his book on "London Labour and the London Poor":

THEY generally consist of boys and girls, varying in age from eight to fourteen or fifteen; with some persons of more advanced years. For the most part they are ragged, and in a very filthy state, and are a peculiar class, confined to the river. The parents of many of them are coalwhippers--Irish cockneys--employed getting coals out of the ships, and their mothers frequently sell fruit in the street. Their practice is to get between the barges, and one of them lifting the other up will knock lumps of coal into the mud, which they pick up afterwards; or if a barge is ladened with iron, one will get into it and throw iron out to the other, and watch an opportunity to carry away the plunder in bags to the nearest marine-storeshop.

1858 was the year of "the great stink" in London. It was a particularly hot summer, and, exacerbated by the increasing use of flush toilets, the river and its tributaries overflowed with waste; cholera was rife. Something plainly had to be done, and Joseph William Bazalgette was the man to do it. As the Chief Engineer for the city's Metropolitan Board of Works, he designed and oversaw the construction of a modern sewage system, the benefits of which we Londoners (and visitors) still enjoy today. And one of those benefits is that mudlarking now carries a much-reduced health risk (rat urine is cited as something to be cautious about, but exactly how that caution should be applied escapes me, and, having just watched Ratatouille, I just can't take it seriously). For yes, mudlarking is a thriving activity along the Thames of central London today, and, as locals, something that we periodically much enjoy - it's fun and it's free. However, we try to indulge in sandlarking, exploring the stretches of beach that appear in places at low tide. The tide is a critical factor - the Thames is a dramatically tidal river, and the battle between incoming waves rushing upstream and the natural flow of the river is a sight to see; the tidal range in central London is between 5 and 7 meters (16 to 23 feet), so timing is critical. As shown in the photos below, there's a patch of largely sandy (but also somewhat muddy) "beach" exposed at low tide just downstream from the Millennium Bridge (the one that used to be wobbly), below St. Paul's Cathedral, and it's easily accessible.

 

And here, from Stephen Croad's wonderful book, Liquid History: The Thames Through Time, is this stretch of the riverside in 1865.

 

Mudlarking today is open to everyone, although there is the Society of Thames Mudlarks, formed in 1980, that issues official permits, with wording such as "on behalf of the Queen's Most Excellent Majesty," and allowing the holder to "search the bed and shore as a recreational pursuit." Digging without a permit is illegal, and any items of value must be submitted to the Museum of London, but digging is not really necessary - the power of the tides and the river itself are more than sufficient to excavate and refresh the banks.

Walk over the sand banks of the Thames and you are walking through history. The banks of this part of the river have been a focus of life and commerce for millennia and the sediment bears witness to this. The surface (see photo above) is covered in natural and manmade detritus, stuff that fell into the river, was thrown into the river, was transported by the river. Oyster shells, roof tiles (some dating back hundreds of years), roof slates, bones, coal, foundry slag, pottery, glass bottles and shards (also a health risk), and thousands of pieces of clay pipes, smoked over a drink on the bank or on a boat and tossed into the river. I am no archaeologist, nor an expert on artifacts, pottery, or bones, but the spectrum of life laid out beneath a mudlark's feet is staggering - and fascinating. The top of a broken frosted glass bottle, a corroded cork still stuck firmly in the neck - who was it that last corked that bottle? The treasures from an hour or so's scavenging are shown below - nothing of any value in a monetary or historical sense, but resonating with value to the mudlarker. Past commerce has included cheap riverside pottery factories, churning out cheap imitations of Delft and Willow patterns - the fragments of designs are a delight. The Whitefriars Glass Works, started in the seventeenth century, and the manufacturer, in 1913, of the stained glass for the east window of the Cathedral of St. John the Divine in New York, stood close to our beach: are the iridescent pieces of slag from there?  

 

And then there is the sand. I have samples of the glorious diversity of sands from around the world, but I realised that I had never collected any of the sand closest to home. Sand, like a cuisine, is a celebration of local ingredients, making use of whatever is available. And, not surprisingly, I found that the sand from the Thames beach is indeed a microcosm of the medley of materials one sees at the surface - plus more natural ingredients. The images below illustrate this. I am, ashamedly, no expert on local geology, but the sand must be a mixture of grains eroded from the upstream reaches of the River, the local geology, and, surely, given the power of the tides, components from downstream towards the estuary. Plus the witnesses of local history and commerce. The city is underlain by the London Clay, but there are many sand beds within that clay, and so perhaps some of the glittering quartz grains are derived from those, or other chapters of riverside geology. Or many of them could have simply fallen off the barges that have carried sand up and down the river for centuries. But the incredibly pure and transparent ones - could they be detritus from raw materials for the Whitefriars Glass Works? I discovered that the works used the world-famous high-purity glass sands from Fontainebleau in the forests outside Paris - could some of these be grains that succeeded where Napoleon failed? I picked out a few individual grains, shown on the right of the picture - clay fragments, bits of bone, bits of slag and coal, glass shards, slate - the microscopic record of the visible history.

 

The microscopic view of Thames sand grains illustrates, yet again, the beauty that lies behind the apparently mundane. And, in looking into bits and pieces of river history, I came across an artist who senses that too. Below is a work by Nicola Rae, titled Five Sands, Gravels, and Mud from the Thames; the sediment-filled cylinders are suspended side-by-side; she comments that

The beach sands and mud bordering the Thames between Deptford Creek and the Thames Barrier vary surprisingly. Different industries on the working wharves have affected the nature of the beach sands and mud.

 

And I'll finish with my own image of Thames beach sand and mud.

 

[for those interested in a mudlarking expedition, information about organised walks can be found at http://www.walks.com/Homepage/Beachcombing_Walks/default.aspx; Nicola Rae's website is at http://www.a2arts.co.uk/nrae/index.html; online resources on London history and the river in particular are extraordinary but I wouldn't know where to begin - the Museum of London is as good a starting point as any.]  

 

Intercalations and a virtual book tour

 

I've just finished reading David Williams' recently published book, Stories in Stone: Travels Through Urban Geology, a title following on from David's eponymous blog and website. It's a great read that satisfies the two primary criteria for non-fiction: informative and entertaining, and there will be more on the book later (see below). As I was reading it, I was struck by the echoes and relationships with my own book, and the archaic word intercalations for some reason struck me as appropriate. It's not archaic in the sense of being no longer in use, but its appearances tend to be rare and rarified - including in geology. I remember standing in front of outcrops and scribbling in my field notebook "blocky sandstones, 10-15 cms, occasional thin shale/siltstone intercalations." I could, in reality, just as well have written "interbeds," since all I was describing was regularly alternating layers of sandstone and shale; but "intercalations" lent gravitas to the description. It's an interesting word - the "inter" part is obvious, but it surprised me to discover that the "calation" is from the same Latin origin as "calendar," and, in turn, "call." The Latin verb intercalare meant to proclaim, and reflects the calling in of accounts on the first day of the month - calends - to be recorded in the calendar, or account book. Amongst other applications, the word has come to be used for inserting extra days into the calendar, as in "February has an intercalary day every four years." Various scientific disciplines have appropriated the word "intercalate" as an alternative for the more prosaic "insert" or "interleave" - molecules can be intercalated with each other, as can various biological items.

So, as I was reading David's book, the image came to me of the connections between Stories in Stone and Sand as interwoven, interleaved, intercalated. It's interesting to me that both of us regard story as critical, and David weaves fascinating stories around the variety of building stones that he has chosen (surely a difficult culling task). But furthermore, I suppose in part because I am attuned to any occurrence of the word "sand" - an obsession which, literally, is satisfied on a daily basis by even a cursory scan of the media, - I was conscious of the recurring role of sand in David's stories. Not just the obvious ones of sandstone as building material - the Brownstones of New York (which featured also in my book) - but in the sense that even the great limestone and marble building stones (including the Carrara), began life as sand banks of biogenic materials and ooliths in balmy tropical seas, that it's intercalated layers of storm-deposited sand that made the extraction of blocks of Florida's coquina stone easier, that, from ancient Egyptian to relatively recent times, sand has provided the abrasive for cutting even the toughest building stones, and that sand can be an unwelcome intruder, a spoiler of the finest quality slate. Geological tales - the discovery of dinosaur footprints by Pliny Moody in the Massachusetts sandstone that told the story of separating continents, James Hutton's revolutionary insights at Siccar Point - feature in both books: it just seems that there are some episodes, some stories, that provide unparalleled access to our understanding of our planet.

The stone stories of David's book will be further explored over the next few weeks by virtue of a blogging innovation - a virtual book tour. The schedule of events is listed at http://stories-in-stone.blogspot.com/2009/08/virtual-book-tour-of-stories-in-stone.html, starting with Brian and Clastic Detritus - http://clasticdetritus.com/2009/08/14/friday-field-foto-89-triassic-sandstones-in-brooklyn-ny/. I am very much looking forward to David's visit to Through the Sandglass at the end of this month.  

[California turbidites used in the image at the head of this blog courtesy Earth Science World Image Bank http://www.earthscienceworld.org/images, Copyright © Marli Miller, University of Oregon]

USGS beach health advice - but let's hear it for meiofauna

The US Geological Survey newsroom has just put out an advisory on the importance of washing your hands after playing in the sand on the beach:

By washing your hands after digging in beach sand, you could greatly reduce your risk of ingesting bacteria that could make you sick. In new research, scientists have determined that, although beach sand is a potential source of bacteria and viruses, hand rinsing may effectively reduce exposure to microbes that cause gastrointestinal illnesses.

Yes, indeed, my mother - and mothers in general - were right: "wash your hands!".

Beach pollution is a significant problem, but things could be a lot worse.

I learned many things in the course of writing the book, but perhaps the most extraordinary revelation was the staggering diversity of minute creatures that creatively and tenaciously make their livelihoods in the miniature worlds between the grains of sand on our beaches. The general term for this microscopic zoo is meiofauna, the "lesser animals." Representatives are shown in the image at the head of this post (photos by M.D. Hooge), and it is their world that Rachel Carson was referring to in The Edge of the Sea, when she wrote "Walking back across the flats of that Georgia beach, I was always aware that I was treading on the thin rooftops of an underground city." And the meiofauna do a heroic job of keeping our beaches clean. Here are a couple of extracts from Sand on the interstitial jungle:

In the great hierarchy of living things on our planet, it is generally accepted that, at the head, there are five kingdoms, one of which—animalia—contains all multicelled animals. Within each kingdom are a number of phyla: all mammals, birds, reptiles, amphibians, and fish belong to the phylum chordata. Depending on which biologist you speak to, between thirty-six and forty total phyla are recognized on our planet. Rainforests, our flagships of biodiversity, are known to contain sixteen phyla. The spaces in between sand grains are home to twenty-two.
..........................................................................................................

The dark, watery world beneath the surface of the intertidal zone of most beaches is home to many kinds of bacteria—and a jungle of other minute creatures. Silica, or quartz-based sands, are the most hospitable, since the calcium carbonate in sands composed of shell fragments makes the water too alkaline for many creatures to flourish. Pick up a handful of wet quartz sand on the beach and you are holding a miniature zoo with thousands of inhabitants. Some of these were first observed by Antony van Leeuwenhoek as he peered down his microscope at sand grains and his animalcules, but we owe our understanding of the incredible diversity and importance of this community to the work of Robert Higgins, who since the 1960s has devoted his life to identifying and describing its members. Now retired from the Smithsonian Institution, Higgins is the pioneer of work on meiofauna (“lesser animals”), creatures whose giants are 1 millimeter long; he continues to contribute to the identification of new species, which crop up at the rate of a dozen or so every year. In a 2001 symposium that paid tribute to his discoveries, Higgins modestly described his work as “how the ‘lesser-knowns’ became better-known.”

Life between the sand grains is not an easy one. The grains move and settle under the pressure of the waves and the incessant flushing of the tides, water occasionally drains out completely, and the ecosystem contains a variety of predators. Life has had to adapt, and it has done so in strange and extraordinary ways that reflect an intimacy with the behavior of granular materials. Many of these creatures have armored or padded bodies designed to withstand abrasion by moving sand grains; their shape is often flat or elongated to enable squeezing between the grains; and they have developed a variety of ways of attaching themselves, using glue or suction, to individual sand grains, clinging on for dear life. Rotifers, nematodes, mystacocarids, tardigrades, gastrotrichs, turbellarians, and kinorhynchs—it’s tempting to view these little animals as rejoicing in their exotic names. Tardigrades, which live in both marine water and freshwater, can’t swim, so hanging on to a sand grain is vital; some use mechanical suction toes, some claws, some both. A gastrotrich can glue and unglue itself in an instant. A kinorhynch is ungainly, described by Higgins as an umbrella in a canister, but it moves effectively, if slowly, exploring one sand grain at a time. Rotifers, so named because they look like rotating hairy wheels, are represented by 2,500 different species, most of which are freshwater dwellers. Tardigrades have the remarkable ability to suspend operations if the water disappears, remaining dormant and dehydrated for a hundred years, only to spring back to life when rewetted. They seem to do this by replacing the water in their cells with sugar, which renders them immune to freezing and radiation, a talent that is of considerable interest in the worlds of medicine and extraterrestrial biology.

In the entire living world, only three new phyla were identified in the twentieth century, and one of them came from the strange world of meiofauna. In the 1970s, Reinhardt Kristensen, a professor at the University of Copenhagen and an old student of Higgins, showed him a collection of creatures from the coast of Brittany that he could not identify. “Oh,” responded Higgins, “I have one of those too.” The animals fit with no known group of living things, and it took several years of meticulous collaborative work to define the character of the creature as a new phylum. It looks rather like a classical amphora with snakes emerging from it, and they named it loricifera, “corset-bearing,” reflecting the appearance of the rings that sheathe the animal. More than seventy species have now been identified, but we know next to nothing about their behavior, since, sadly, they die before reaching the laboratory. One remarkable thing we do know is that loricifera have the smallest cells of any known animal.

Inevitably, the community of organisms growing on or living in sand has its own name: psammon. Among the psammon are psammophiles (or arenophiles, if you prefer Latin to Greek), psammobionts, and psammoxenes. The names are weighty, but the members of the community are not; what they are is wondrous. Most of us don’t know they exist, but we should be grateful for them. Without meiofauna, the sands of our beaches and lakeshores would be stinking, toxic places, with organic debris rotting unconsumed and dangerous bacteria rampant. The microscopic creatures of the meiofauna feed off this debris: they keep our beaches clean.

[for more information on these fascinating creatures, see the site of the network of 94 European marine institutes, http://www.marbef.org/wiki/Meiofauna_of_Sandy_Beaches, the International Association of Meiobenthologists at http://www.meiofauna.org/, http://discovermagazine.com/1995/apr/lifeonagrainofsa491, and http://whyfiles.org/022critters/meiofauna.html, the latter particularly on Higgins.]

Fleeting Fame: "Sand" on "Fast Draw"

Amazon sales rankings are somewhat like Fermat's Last Theorem - what they're saying makes apparent sense, but discerning how they work is seemingly impossible. Nevertheless, the fact is that they are routinely (obsessively?) scrutinised by writers - and that includes me. At least, I tell myself, the relative movements of the ranking are indicative of something, even if they contain no absolute information. Earlier this year, Sand attained a heady rank in the 5000s of total book sales, an achievement that gave me some pleasure since I felt I could visualise a wall of shelves with 5000 books on them and, on the bottom shelf on the right, Sand. But most of the time the book inhabits the five-figure ranks, periodically wallowing in the quicksand of six figures.

And then, on August 2, I was startled by a strangled cry from my wife on the computer downstairs - I rushed down, desperately trying to focus poorly formed recollections of how to perform the Heimlich Maneuver (or Manoeuvre - I couldn't even remember how to spell it), to find her transfixed, pointing with a shaking finger at the monitor. My Amazon ranking was 572! No, that's not a typo, I was rubbing spines with the stars - well, not, of course, the Harry Potters, but a shelf of five hundred or so books is simply a small section in a chain bookstore. The book was number one in various "natural resources" and geology categories.

This was a complete mystery - what could it mean? Had Amazon been attacked, had their famous software finally gone haywire? Or (my fondest aspiration) had some far-sighted educational institution seen the value of Sand as a text for a "rocks for jocks" or "Environmental Studies 101" course? The publishers at the University of California Press were equally bemused - pleased but bemused.

Now I know what happened. Some time ago, I'd been contacted by Josh Landis. Together with Mitch Butler, he is co-creator of CBS News’ "The Fast Draw," an animated news series appearing on a number of CBS News broadcasts, including CBS Evening News with Katie Couric and CBS News Sunday Morning. He had told me that they were preparing a short segment (all of their pieces are just a few minutes in length) on sand - he wasn't sure when it would be broadcast. Having heard no more, I had forgotten about it, but we've now discovered that it went out on yes, August 2, and included a reference to the book. Wow. Of course, I have no idea whatsoever how many actual books were sold as a result, but it must have been this that caused the uplift, the orogeny, in the Amazon numbers. The Fast Draw segment, titled "Lessons of Sand" can be viewed online here - it's entertaining and only three minutes long.

The Amazon ranking as I write this? 21,239. The UK Oxford University Press edition is officially published on Thursday. It has a slightly different title - but that's another story. Amazon UK ranking? 109,085 - but my fingers are crossed.

"Sand to Chips" - what's the real story?

One of the thorny issues that I grappled with in writing the book was how to review the staggering number of ways in which sand is important in our lives - in the end, the diversity was so overwhelming that I resorted (as readers of the book will know) to an alphabetic medley approach; interestingly, it would seem to be a chapter that is often highlighted in reviews and comments as either highly entertaining or awkward. In my ruminations about how to weave all these disparate topics in to  a narrative, one idea had occurred to me: given that an immediate and recurring (if subconscious) encounter we all have with quartz sand is every occasion that we use an electronic device, why not tell the story, the journey, of a sand grain from its geological origins to the silicon chip in the computer on which I was writing?

"Sand to chips - a biography" - seemingly a simple task, this proved anything but. To begin with, given the need for various but rigorous levels of extreme purity in silicon-based manufacturing, just any old sand won't do - the raw material has to be as pure as possible to begin with. As I wrote:

First of all, the public is understandably more interested in the technology of making the silicon chip than in its provenance in a sandbank by a river somewhere. Second, the absolute volume of semiconductor-grade silicon is only a small fraction of all silicon production. But more important, a small number of companies around the world dominate the technology and the market, and while their literature and websites go into considerable and helpful detail on their products, the location and nature of the raw materials seem to be of “strategic value,” and thus an industrial secret. I sought the help of the U.S. Geological Survey, which produces comprehensive annual reports on silica and silicon (as well as all other industrial minerals), noting that statistics pertaining to semiconductor-grade silicon metal were often excluded or “withheld to avoid disclosing company proprietary data.” The survey staff were, as always, extremely helpful, but were themselves perplexed that such an apparently simple question was not simple to answer. They put me on the trail of a number of sources, but telephone and e-mail inquiries did not shed a great deal of light. What I could deduce is this: the common source of silica for manufacturing the high-purity grades of silicon used for, among other things, silicon chips is not loose, unconsolidated sand from a beach or river sandbank, but sand that has already been ultrapurified by nature: quartzite.

Quartzite is a rock that was originally a silica sandstone; it has been so deeply buried in the Earth’s crust, cooked by such high temperatures and pressures, that many of the impurities have been distilled out and the sand grains completely annealed and welded together. Hit quartzite with a hammer and it rings like a bell because of its hardness, purity, and uniformity. Hit it hard enough and it breaks across the ghosts of the grains, not around them. Quartzite can be well over 99 percent pure silica. Grind it up to a powder of a consistent grain size and it’s a good starting point for making silicon.

The geological kitchens of the Appalachians were good at making quartzites, and my research (including phone calls to sand and gravel suppliers) led me to one possible source:

The Coosa River, for example, originates close to the border of Georgia and Tennessee and, together with its tributaries, drains a large and geologically diverse area of Appalachian rocks, including quartzites. It crosses from Georgia into Alabama, where it joins the Tallapoosa to become the Alabama River. As it does so, it enters the broad coastal plain, slows down, and dumps its sediment load. Large volumes of aggregates for all kinds of industrial purposes are extracted in this part of the country from the sediments of the Coosa and other rivers, but among those everyday aggregates are pebbles of great value—pure quartzites from the kitchens of the Appalachians. And those, I believe, are one source of raw material for high-grade silicon. So it’s true that computer chips are made from sand—but sand that was first deposited several hundred million years ago.

But the confidence level that I (and the USGS) had in this being a definitive example led me to abandon the sand grain biography idea. Then, earlier this week, the whole issue arose again: BBC Radio in the UK had a programme (it is the BBC, hence the extra "me") called "Chips with Everything" and an associated article titled "Silicon Valley's Secret Recipe." The thirty-minute broadcast is well worth listening to, for the "Silicon Valley" referred to is in the Blue Ridge Mountains of North Carolina, around the small community of Spruce Pine which calls itself the Mineral City - for good reason. The programme is culturally fascinating but also highly informative with respect to silicon chip technology - and I learnt something that I had missed in the opacity of my earlier research.

The reason the Spruce Pine calls itself the Mineral City is that in the surrounding hills is a treasure trove of precious and highly valuable industrial minerals - including some of the purest quartz in the world. These minerals, exploited since long before the ancestors of today's residents arrived, are contained in igneous rocks, solidified from molten material deep below the earth's surface; but these are special, rocks that are made up of unusually large and unusually pure, crystals - rocks called pegmatites. Below is a photograph of one of these (thanks to Callan at NOVA Geoblog), with large feldspar crystals embedded in quartz. It was long thought that these unusually obese crystals formed because the cooling rate of the molten rock was extremely slow, but this apparently logical model has been replaced by recent research that suggests that the cooling rate was unusually rapid, faster than the rate of crystallisation could keep up with.

 

The hills around Spruce Pine have been described as the most valuable strategic acreage on the planet. Sixty-eight-year-old Ira Thomas, a ninth-generation Spruce Pine miner who used to dig up aquamarines and prospect for mica as a child justifies this description: “Because the world runs on computers, we all know that now. And if we locked the gates to Mitchell County they could not make any more computers.” As a consequence, the quartz pegmatite mines are protected by security akin to the Pentagon or the Bank of England. Spruce Pine is billed as the world's only source of this uniquely pure quartz - this is geologically probably not quite true, but it is by far the world's major supplier of a raw material that sells for $50,000 a ton.

But so what was my revelation? Simply that the Spruce Pine quartz is valuable not as the source of silicon for chips, but as the material for making the crucibles and other bits of kit needed to process electronic-grade silicon. Silicon can be extracted from any quartz relatively easily (you can do it, albeit somewhat dangerously since silicon is an excitable element, in your kitchen from beach sand); but to process it to the level of purity needed, then ultra-pure equipment is essential - and it's made from Spruce Pine quartz. The level of silicon purity for a chip is extraordinary: electronics-grade silicon has to be at least 99.99999 percent pure - referred to in the trade as the “seven nines” - and often it’s more nines than that. In general, we are talking of one lonely atom of something that is not silicon among billions of silicon companions. Or, as a Dow Corning scientist, put it:

Imagine stringing tennis balls from the Earth to the moon, and wanting them all to be yellow. He said this would take about 5.91 billion tennis balls. For the color coding to be of semiconductor quality, "you could only tolerate two, maybe three that were orange," Lane said. For solar cells, which are slightly less demanding, Lane said, "You could tolerate five or six orange balls."

Following up on the BBC material, I came across a useful series of articles on Geek.com, which, in turn, led me to a press kit put out by Intel, titled "From Sand to Silicon: the Making of a Chip." And there, to my delight, at the head of the document is an image of a pile of sand. One of the Intel images is at the head of this post, and in the document is accompanied by the description:

Sand

With about 25% (mass) Silicon is –after Oxygen –the second most frequent chemical element in the earth’s crust. Sand –especially Quartz -has high percentages of Silicon in the form of Silicon dioxide (SiO2) and is the base ingredient for semiconductor manufacturing. [my highlighting]

The silicon is purified in a series of technologically sophisticated (and highly secret) steps; to the right of the pile of sand is melted silicon, and then a "Mono-crystal Silicon Ingot .... produced from Electronic Grade Silicon. One ingot weights about 100 kilograms (=220 pounds) and has a Silicon purity of 99.9999%." (Why six, not seven, nines?)

So there we have it - sand, or potentially sand in its quartzite incarnation, is the source of raw silicon for electronic chips. But I am no further forward on identifying geologically which sands - or sandstones, or quartzites - are the sources. The quest continues - if anyone can shed light on this, I would be hugely grateful: I can provide an update for the paperback edition of Sand!  

 

[My profound thanks to Pete Modreski at the USGS for his continuing help throughout this quest. And there are other sources of high purity quartz in the world, among them from Norway: the NGU, the Norwegian Geological Survey, has an excellent web page, in English, on high purity quartz -  http://www.ngu.no/no/hm/Georessurser/industrimineraler/Kvarts-og-kvartsitt/Hoy-ren-kvarts/]

 

The Poetry of Sand: Guest Writer, Richard Bready

Times of Sand

Richard Bready

 

                                          In science one tries to say something that no one knew before

                                          in a way that everyone can understand. Whereas in poetry . . .

                                                   - Dirac (1)

 

I

              The foam along the beach stands up like hills

Seen from aloft. On foot, nine birds patrol

The intertidal zone, their tweezer bills

Ready to pluck small life from every hole

It digs when stranded. This arrangement fills

A fractioned second’s record on a roll

Of photographic film: sand, bubbles, ocean,

And sanderlings, all frozen in mid-motion.

 

              As regular as clockwork toys, the birds

That flee then follow each collapsing wave

Have wound down, count by count, until two thirds

Of once-reported numbers fail (2). To save

Some quotient of those running, time and words

Both fly. The key resource the waters gave

Has new consumers now; supplies of sand

For living on or living off the land

 

              Are limited. The hills, time-lapsed, like foam

Slide flat, flowing in streams back to the sea,

Where many a tiny being makes its home,

Armor and armature, out of the free

Stone molecules dissolved there. Breakers comb

Shell fragments with eroded quartz debris

Of antique landscapes. As these grains combine,

Exceeding slowly and exceeding fine,

 

              A longshore current wipes them sideways. Beaches

Ribbon the coast. In summer, gentle, warm,

Soft-crested rollers fall upslope, and each is

Depositor of sediment to form

Wide flats that winter waves from wind-whipped reaches

Narrow and steepen. Heaped and scraped by storm,

Or levelled by the leavings of fair weather,

The shoreline ebbs and grows. Taken together,

 

              All factors average out so that the coast,

Decade to decade, does not show a lot

Of difference, although in fact almost

The whole has shifted from some previous spot

And will abandon soon its present post.

Dynamic equilibrium is not

A property desirable to buyers

Of property. The migratory fliers

 

              Go elsewhere in lean years for body fat

To fuel them to their tundra nests and fill

Their eggs with calories (3), or, lacking that,

Don’t reproduce (their populations spill

And soar in curves that match their habitat),

But owners, fixed like barnacles, hold still,

A constancy against which every loss

They suffer from the local pitch and toss

 

              Is measured for resentment, as a waste

Of time, of money, spent here to secure

A territory. Watching it defaced,

The beachfront houses by the sea unsure,

The nesteggs threatened, paradise misplaced

Perhaps for years, they think themselves landpoor,

Demand that conservation keep more change

From harming them, and to this end arrange

 

              Groins, jetties, bulkheads, breakwaters, seawalls,

A coastal incrustation hoped to hide

The land that’s shrinking from the wash. Yet all’s

For naught. What order given to the tide

Will stop or slow its motion? In it crawls

And out casts castles pride had fortified

Regardless of the cost. Wave guides, sand traps

Hasten erosion (4). Beaches found on maps

 

              Are lost at sea now, littorally vanished.

For birds, there is no other shore to go

To on the other side; or, they are banished

From remnant feeding grounds by flocks that grow

Whatever happens: busy, noisy, tannish,

These eat, these swim, these bask, run to and fro

For their own reasons, dig, call, squabble, read,

Drive Jet Skis® and dune buggies at high speed,

 

              And make the scene intolerable, except

For such as gulls, who share a human nature

And profit from increase of garbage. Kept

From food or rest, a less aggressive creature,

Thinner for each horizon overleapt

To beat retreat from beasts of greater stature (5),

Flies on, dies on the way perhaps, ends there

Its piece of time with water, earth, and air.

 

II

                                          For us believing physicists, the distinction between past, present,

                                          and future signifies only an illusion, if a stubborn one.

                                                 - Einstein (6)

 

Two million years or so ago (7), when ice

Platemailed the planet, sanderlings were trotting

Seasidelong back and forth at their precise

Escapement distance from the wavefronts plotting

A line on continental shelves where twice

The modern inshore verge rose dry (8): allotting

Less runoff to each river as they grew,

The glaciers made sea level drop. All through

 

              Those twenty thousand centuries of freeze-

Thaw seesaw tides, a pendulum has swung,

Now with slow fastnesses of crystal seas

Towering above parched prairies, now among

The headlong meltdown torrents that with ease

Have carried megatons to fill the young

Wide-open river mouths with sand and silt,

Which risen oceans gradually rebuilt

 

              As barrier island, beach, bar, shoal, or spit,

While flattened barrens shed their load of frost,

And pioneering lichens bit by bit

Cracked rock to soil. Grown fertile, sedged and mossed,

Swarmed in sextillions, warmed through long sunlit

High-latitude spring evenings, land forelost

To life, recovered by that layer bloomed

And buzzed until the glacial spread resumed.

 

            The yearly birds flew north as they do now

To country so congenial for breeding,

Its densities of prey sometimes allow

A pair to double-clutch (9), each parent leading

The brood it hatched. Birthrate increase is how

They best exploit their ice edge niche, succeeding

By an excess that balances, all told,

Eggs eaten, fledglings dead of sudden cold,

 

           And juveniles not most of which survive

The first great journey southward. Shorter days

Trigger the hormones governing their drive

To longer flight. They travel unknown ways

Hinted by instinct’s “Warmer” and arrive

At a new sight, of splashing water—bays,

Coves, estuaries, gulfs—and a new urge:

To eat along the outswash by the surge.

 

              Food is their fate now, find it or become it,

With migrant raptors waiting to attack

Flocks fear assembles; though each day kills some, it

Spares others, safe in numbers. Any lack

Of intake is as lethal. Rule of thumb: it

Requires one week’s weight gain to win back

Strength spent while flying several dozen hours,

Two miles up, at the limit of their powers,

 

              As they must, several times (10). Such wingwork done,

The autumn equinox sees them beside

Six continents, three where the tropic sun

Will follow, three where residents abide

Gale, chill, and dark. Metabolisms run

So fast in them, they take these in their stride,

For nearer birds find, when they next set forth,

Prime sites available throughout the north.

 

              The latest species in its genus (11), fleet

And strong, evolved for margin profits, goes,

Like dawn-age horses as they found their feet,

Tiptoe for speed and so needs no hind toes (12).

Well suited to life’s cycles by a suite

Of adaptations, its long history shows

(Say twice (13) the mean survival of the myriad

With which it shared the Quaternary Period

 

              And twenty times (14) the talking hominid’s),

It faces now a geologic chasm:

A mass extinction, when the planet rids

Itself of life-forms in a rapid spasm

Of death and taxa. What has greased the skids?

Intelligence, that popular phantasm,

Modern mutation, prototype, quick fix,

Like feathers on an archaeopteryx,

 

              Plus sociability, an old improvement

Updated to let many use some’s clever

Ideas in ways the few might disapprove, meant

As thought seems for a higher flight. However:

The birds, the years, the periodic movement,

Waving goodbye, off to the big fornever—

These cannot cease to be. As physicists

Know well, time past, past reaching, still exists.

 

III

                                          The notion of analogy is deeper than the notion of formulae.

                                                 - Oppenheimer (15)

 

              The moment that the motor shot the shutter

Across its aperture made light of time,

Set permanent as particles waves’ flutter

In dye-grain diagram, their fall and climb

A message to the future, written water

Formed firm here, framed here, orderly eye rhyme.

Cross-section of an instant and location,

Now reproducible from information

 

              Locked in its dots, on any page or screen

By ink or current, image can outlast

Occasion, lives, and place. The pictured scene,

Once out of site and into mind, broadcast

Through spacetime, will in changeless silence mean

The singular event—aloud, amassed—

When and wherever probability

Distributes copies. Versatility

 

              Makes sand a subject, means, and measure. Melt

Quartz crystals, then cool quickly; they will change

From solids, patterned molecules all dealt

In face and edge and angle, to a strange

Irregular stilled liquid that is felt

To be a crystal though its parts arrange

Themselves amorphously, which is why glass

Slows light so bends light but lets most light pass,

 

              Lens-gathered to a focus (some reflects,

And windows kill a billion birds a year (16),

Brains bloodied by false azure). What detects

Incoming photons and gets camera gear

Adjusted, bright or dark, as it directs,

Is sand again. Cooked, oxygen will clear

Out of its silica. The siliconic

Atomic lattices for electronic

 

            Controls and sensors slice time even thinner

Than wristwatch quartz vibrating at a snappy

Two-to-the-fifteenth cycles. But the winner

On small scales is the theoretician, happy

To calculate a metric for the inner

Dimensions of the quanta - as a frappé:

Instead of worldline sequences, fluxed foam

Of separate points, past, present, and to come,

 

              And here a place and there a place, yet such

That none leads to another, though they share

Contingent borders, layered nothing much

Between the megagoogolths really there (17).

So water’s surface tension keeps in touch,

Its clingfilm tight around the pressure air

Stirs into it, the contour of a bubble

Upheld by balanced forces in their double

 

              Act. Crossing from one compound to the next,

Repeatedly, refractedly, bounced back

And froth-diverted, light rays, veering, flexed

Along a zigzag and redundant track,

Writhe off in all directions. Sight, thus vexed,

Perceives an opaque white, a shadow black

As if from density, the same way clouds,

Mere pressure gradients collecting crowds

 

              Of droplets, can seem stiff as any stone

That clouds erode with rain and snow while falling

To gravity, the leveller. Downthrown,

Sandpile and surf combine, one smoothed, one sprawling,

To shape a fleeting looking glass: birds shown

Inverted, rippled, blue background recalling

The air, where particles that scatter light

Favor this color’s energy. From flight

 

              The birds drop to a triple point, of sky,

Land, sea, the basic phases matter shifts

As ever since that eon when the dry

Young planet outgassed water at such rifts

As now spread underwater. Floating high

On flowing rock, each continent that drifts

Has closed and opened oceans, heaved up coasts

In mountains, ground those cloud-compelling hosts

 

              To rubble nubbins, and then sand. The age

Of any grain on any hand may be

More than two thousand million years (18), by stage

In magma, granite, river, delta, sea,

Stone, uplift, ice, beach, dune, and desert. Gauge

Of deep time, it implies activity:

To crystallize what little bit one knows,

In chance and change, an angle of repose.

.....................................................................

 

I have commented before on the pleasures that this blog has brought in putting me in contact with people I otherwise would not have known. Here is a quintessential example. This evocative and provocative poem is published here courtesy of the writer, who describes himself as follows:

Richard Bready retired this year from a career mostly spent working on dictionaries and encyclopedias. He lives on the Seattle Fault. His email is [email protected]

The heading image is by MW and the references in the poem are:

1. Quoted in Oppenheimer, J.R. Age of Science 1900-1950. Scientific American, September 1950. p. 20
2. Myers, J.P. The Sanderling. Audubon Wildlife Report, 1988/1989. Howe, M.A., Geissler, P.H., and Harrington, B.A. Population Trends of North American Shorebirds Based on the International Shorebird Survey. Biological Conservation, 49 (1989). pp. 185-199
3. Klaassen, M., et al. Arctic Waders Are Not Capital Breeders. Nature, 413, 25 Oct. 2001, p. 794, discuss the question whether nutrients in eggs of tundra-breeding sanderlings are gathered on migration or on the breeding site, arguing for the latter and citing support for the former.
4. Kaufman, W., and Pilkey, O. The Beaches Are Moving. Duke Univ. Press, 1983. passim
5. Highsmith, R.T. No Rest for the Weary? Conservation Sciences, Summer 1997. pp. 18-20 
6. Albert Einstein, Michele Besso, Correspondence 1903-1955, ed. P. Speziali, Hermann, 1972. p. 538 (to Besso’s daughter and son-in-law after Besso’s death)
7. Emslie, S.D., and Morgan, G.S. A Catastrophic Death Assemblage and Paleoclimatic Implications of Pliocene Seabirds of Florida. Science, 264, 4/29/94. pp. 684-685
8. Davis, R.A., Jr. The Evolving Coast, W.H. Freeman, 1993. pp. 32, 51
9. Lenington, S. Evolution of Polyandry in Shorebirds. In Behaviour of Marine Animals, 5. Shorebirds: Breeding Behaviour and Populations, ed. J. Burger and B.L. Olla. Plenum Press, 1984.  pp. 151-166. Gill, F.B. Ornithology. W.H. Freeman, 1990. pp. 302, 311
10. Castro, G., and Myers, J.P. A Statistical Method to Estimate the Cost of Flight in Birds, Journal of Field Ornithology, 59(4). pp. 369-380. Ibid and Rickles, R.E. Ecology and Energetics of Sanderlings Migrating to Four Latitudes. Ecology. 73(3), 1992. pp. 833-844. Castro, G. Energy Costs and Avian Distributions: Limitations or Chance?—A Comment. Ecology. 70(4), 1989. pp. 1181-1182. Myers, J.P., Maron, J.L. and Sallaberry, Michel. Going to Extremes: Why Do Sanderlings Migrate to the Neotropics? Neotropical Ornithology. Ornithological Monographs No. 36
11. Evolutionary hypothesis, taxonomic history, as until recently named Crocethia alba. Choate, E. Dictionary of American Bird Names. Gambit, 1973. p. 118. Matthiessen, P. The Wind Birds. Viking, 1973. p. 80
12. Heinrich, Bernd. Why We Run. HarperCollins, 2002. pp. 159-160.
13. May, R.M., Lawton, J.H., and Stork, N.E.: Assessing Extinction Rates; Ehrlich, P.R.: The scale of the Human Enterprise and Biodiversity Loss, both in Extinction Rates, ed. Lawton and May, Oxford, 1995. pp. 1-24 and 214-226, especially pp. 2, 3, and 220. Chapters in the same work by Coope and by Thomas and Morris indicate that prey species, in contrast, are coevals.  
14. Bickerton, D. Language and Evolution. U. Wash., 1995. pp. 68-70. Lieberman, P. Uniquely Human. Harvard, 1991. pp. 36-73
15. Electron Theory: Description and Analogy. J. Franklin Carlson Lecture, Iowa State University, 1955
16. Klem, D. Glass and Bird Kills: An Overview and Suggested Planning and Design Methods of Preventing a Fatal Hazard. Wildlife Conservation in Metropolitan Environments, National Institute for Urban Wildlife Symposium, Set 2
17. Wheeler, J.A. and Patton, C.M. Is Physics Legislated by Cosmogony? in The Encyclopedia of Ignorance, ed. R. Duncan and M. Smith. Pergamon, 1977. pp. 38-64 (originally in Quantum Gravity, ed. C.J. Isham, R. Penrose, D.W. Sciama, Clarendon, 1975). Hawking, S.N., Page, D.N., and Pope, C.N.: Quantum Gravitational Bubbles. Nuclear Physics B170, 1980, pp. 283-306
18. Siever, Raymond. Sand. W.H. Freeman, 1988. p. 217