Category Archives: Digressions

Stabilisation of an architectural icon; the Leaning Tower of Pisa

Sunday in Pisa proved to be a welcome change from the usual tourist-cramped, shoulder-barging throngs of popular attractions in Tuscany.  No problem finding a seat in a decent café, en route to the Piazza del Miricoli.  Cross the street, turn a corner and there – the massive, white-marbled Pisa Duomo, Romanesque grandeur with a veneer of 21st Century scaffolding.  But the sense of balance normally attributed to cathedrals, is disrupted by the stand-alone bell tower that leans precariously, like a drunk looking for a lamppost.  The Leaning Tower of Pisa has been looking for a lamppost for almost one thousand years.  And for a thousand years, people have been drawn to the tower not because it is particularly beautiful, but because it looks like it is about to fall over. Continue reading


A measure of the universe; Renaissance slide-rules and Heavenly spheres

Measurement is a cornerstone of science, in fact of pretty well everything we do: How far? How fast? How long?  We take most measurement for granted, with little thought to how the process originated.  We demand accuracy and precision, forgetting that these are relatively modern luxuries.  Before the universal clock chimed GMT in 1884, there were more than 200 time zones in the US.  A league in France was shorter than a league in Spain, a discrepancy for which the 16th C French scribe François Rabelais had an imaginative, if rollicking explanation.  In his tale, The Life of Gargantua and Pantegruel (1532-1564), a king required a standard distance to be determined (after all, if he was going to send his armies to battle it would be best if his advisors new how far they had to go).  He sent a trusted Knight, instructing him to ride to Spain, stopping every league to “roger and swive”; hence the discrepancy.  The leagues gradually became longer. The amusing satire of this explanation had its roots in real Medieval measures; the width of a hand, the distance one could walk in an hour. Continue reading


Galileo’s finger

“Their final resting place…” a sepulchral phrase, redolent of a fate that awaits us all.  There is no doubt as to its finality, but resting…?  A nice metaphor that may convey a sense of comfort to the living, rather than the deceased.  Wander through any church or cathedral in Europe and Britain, and you will inevitably walk over cold marble slabs, engraved with the details of those who lie beneath, polished by the feet of a myriad worshipers and tourists.  The Basilica di Santa Croce in Florence is, in many respects, like any other magnificent church; it is old, construction beginning in 1295, with alterations and additions during the 14th -15th century overlapping the earlier Gothic forms.  The Basilica is stunning, but differs from many of its contemporaries in that it became THE place in Italy to be buried. Continue reading


The life of a Tuscan wall

Montefioralle, Chianti country, Tuscany, Italy, and from where I’m sitting (happily sampling a Chianti Classico) I see rolling, wooded hills, next season’s vintage, olive groves a scattering of farm dwellings, and rock walls. Quintessential Tuscany. Except for a few ratty road cuts, there is little native rock exposed in this part of Tuscany from which a keen geologist might ascertain something of ancient pre-Tuscan history (farther south this changes).  But in fact, there are rocks aplenty. Most walls (houses, defensive, retaining, decorative) are made of limestone and sandstone, some quarried and deliberately shaped as in churches and castello (that date back to the 10th -11th century), and others that made use of whatever was handy at the time. Most of these materials were collected locally; stones that littered the hillsides, and stones brought to the surface during ploughing.  Even today, ploughs bring stones to the surface; the local clay-loam soils are incredibly stony (an important part of Chianti terroir).

So, despite the paucity of hard-rock exposure, one can make a reasonable guess at the geology beneath the hills and vineyards, based on the stone composition in local buildings. About 50-60% of the stones are cream-coloured marls; marl is an old name (medieval Latin) given to very fine grained, usually muddy limestone that breaks along curved, sharp-edged surfaces (referred to as conchoidal).  The Tuscan marls are very hard – ideal for building stone.  Variations on this theme include sandy limestones, some of which contain intricate contorted layering, and small crossbeds that indicate flowing water many millions of years ago.

Grey sandstone is also common; in fact it is found as paving stone throughout most of Tuscany.  All kinds of structures are visible in these stones, especially cut stones in larger buildings and roads; fossil ripples that indicate flowing water, trails and burrows of critters that moved across or below the ancient seafloor in search of food or finding a place to live. Some of the sandstones are not as hard as the marls, and in places show quite advanced damage where bits of rock fritter away with the vagaries of weather.

An assortment of red bricks, some rumoured to be of Roman or Etruscan derivation, has been used in most walls. It looks like odd-shaped bricks are filling equally odd-shaped gaps, but they have also been used to replace stone arches over doors, or fill holes in walls left by marauding armies (of which there were many) or neglect.

The rocks were originally deposited as sediment in an ancient and vast ocean called Tethys, that separated two supercontinents – Gondwana, and Laurasia (most of Europe and Asia).  The Tethys was closed when the Africa plate (part of Gondwana) drifted north and crunched into Laurasia, beginning about 65 million years ago. The resulting uplift produced the Apennine Ranges that now course the length of Italy.

Montefioralle is a picturesque hill-top village, typical of many in Tuscany.  Its medieval origins are still visible, but frequent battles between neighbouring villages, as well as larger fracas between Florence and Siena, put a few dents in the outer wall and houses. The hill top is crowned by a small church and tower; the last refuge in the event of siege.  There is clear evidence of repairs made over the last 800 plus years, including, I suspect, some from a more recent European conflict.

Stones in these Tuscan walls weave their tales in different threads. The limestones and sandstones have a geological story that spans 10s of millions of years, the disappearance of an ocean and the collision of continents.  Each stone and brick can also relate centuries of local history; each was carefully placed by someone, a stone-mason or perhaps a Renaissance DIY. Nameless, we can admire their handy-work, wonder what they talked about with their fellow workers, what they ate, who they loved.  There are centuries of these former lives everywhere in Tuscany. Chianti Classico loosens all their tongues.


A very British Library

Being acquainted with things that are really ancient, is an everyday experience for a geologist; fossils and other flotsam of lives past, meteorites as old as the solar system itself. Records of these ancient lives, their successes and failures, of catastrophes, of ancient worlds, are written in every chip of rock, every grain of sand. We marvel at these stories, at their old-ness. My recent visit to the British Library in London was a reminder that our written history is also ancient, but counted in millennia rather than eons.  I’m talking books and parchment, not carved cuneiform tablets. These treasures are housed in a room of the same name, light and humidity controlled, protected from hands that would love to turn the pages. Sensible precautions of course; many of these pieces would probably disintegrate at the slightest touch.  I’d never seen the sole-surviving copy of Beowulf, an original Gutenberg or King James Bible, the Magna Carta, a 3rd Century fragment of a Gospel, a Thomas Tallis liturgical composition. So many documents that record our history and inform our present.

The 4th century Codex Sinaiticus, the earliest complete New Testament plus some of the Old Testament books (in Greek), has few of the embellishments that characterize many younger religious manuscripts, but the actual lettering is incredibly uniform, beautifully written; whoever did the job must have spent years at it. There is an ancient copy of the Quran open at a page that tells of Gabriel’s revelations; I’m not sure if this was a deliberate choice of verse on the part of the Library organisers. Some younger texts, like the 9th century Harley Golden Gospels from Charlemagne’s court, or the first English translation of the Newe Testament by William Tyndale (1526) show the painstaking effort for uniformity of elaborate, Gothic-like text liberally sprinkled with the kind of artwork, rubrics, and gold ornamentation that seemed popular at the time.  I guess the people who wrote these texts (mostly monks) had plenty of time on their hands because these projects usually took years to complete. How on earth can someone spend that amount of time basically copying someone else’s work; what were they thinking as they scrolled and scribbled. Perhaps they chatted among themselves, local gossip, intrigues (secular and ecclesiastic); maybe something like “I hear Brother Bartholomew was dismembered the other day for suggesting the earth revolved around the sun”.  Telling stuff.

Other than making it up, it is almost impossible to get into the minds of these scribes; each may have had an inconspicuous, renaissance equivalent to an emoji, surreptitiously incorporated into the last page, but these manuscripts, beautiful as they are, were largely impersonal.  Unlike the ecclesiatics, people of letters, like Jane Austin, George Elliot, Oscar Wilde and Winston Churchill, left a much richer record of who they were, their loves, their foibles.  Anyone can now read almost anything these people wrote, via hardcopy or digital.  Immersing oneself in books – the cellulose kind –  is still an accessible pleasure. We take reading for granted.  But a reading populace is a relatively recent consequence of writing.  The Gutenberg Bible is famous for being the first major document to be printed on a press with moveable type (1455). Invention of the printing press is one of those (commonly) understated paradigm shifts in western society; every person could, potentially, learn to read. This proved to be hugely annoying to the Church, who regarded a literate population as an affront to their, and therefore God’s, authority.  After all, you can’t rule people who read things that enable them to make up their own minds about life and beliefs.

There were very few scientific documents in the collection I visited. I was hoping to see something of Galileo, Einstein, or Darwin, but I’m guessing they were filed away somewhere.

That any of these paper documents has survived, particularly those that are almost 2000 years old, is remarkable. Seeing the collection was a reminder of how precarious the recording of history can be; it could disappear in a moment, through an act of violence, neglect, or wilful denial. It was an affirmation that people throughout history have understood the value of preserving the progress of humanity. I am very grateful that they did.


A Watery Mars; Canals, a duped radio audience, and geological excursions

Deceptive news is the art of pulling wool over the eyes of the populace, a tool (recently resurrected by certain politicians) for persuasion or dissuasion.  Orson Welles got more than he bargained for when, on October 30, 1938, he orchestrated a radio adaptation of H.G. Wells The War of The Worlds, a 1898 sci-fi that pits intelligent Martians against Victorian Britain.  Welles broadcast created a mix of amusement in some commentators, and in others panic and anger; panic in the unwitting, anger in the duped (especially other broadcasters), and amusement in all the above.

Well’s novel, apart from being the product of an agile mind, was influenced by some of the popular astronomical ideas of his time.  Italian astronomer Giovanni Schiaparelli produced, in 1888 a wonderfully detailed map of Mars showing (above image), among features such as seas, islands, and other landmasses, a network of ‘canali’, or channels.  Canali was misinterpreted in English as canals, and along with all its connotations of intelligent life, the idea of Martian canals entered popular belief.

Were the anthropomorphic connotations of the word canali deliberate?  Percival Lowell, a self-made American astronomer certainly thought so.  In 1894 Lowell announced his own findings, that there were indeed canals, 100s of them, many of them straight, intricately networked, and all artificial, which of course meant intelligent beings.  H.G. Wells simply expanded Lowell’s ideas to the point of delightful absurdity.  That O. Welles would later foist his version of events on an unsuspecting public seems quite reasonable.

Since the 1970s we have been projecting our own intelligence and sense of puzzlement on Mars, using satellites and landed vehicles.  There are no artificial canals, but there are canyons, channels and gullies, landforms that bear an uncanny resemblance to terrestrial analogues.  There is now a significant body of evidence to indicate that Mars was once watery.

On earth, sediment is distributed far and wide by flowing water. Very fine sediment from rivers or wind-blown dust is commonly suspended in water; the sediment gradually settles on the sea or lake floor.  Coarser sediment, like sand and gravel tends to be ‘entrained’ close to the sea floor or river bed by fast flowing water.  Sediment that is moved in this way forms a variety of structures such as ripples and larger dune-like structures.

Rivers in particular, generally move sediment to larger repositories, or basins such as seas or lakes; The kinds of landforms that represent these processes are very distinctive.  On Mars, there are several landform-indicators of flowing liquid (most likely water), most of which have direct terrestrial counterparts; deltas, straight and meandering river, point bars, alluvial fans, and gullied crater margins.  One such Martian landform, imaged by NASA’s Mars Global Surveyor, is the Eberswalde Delta which contains many of the ingredients that also make up terrestrial deltas.  In this case, sediment making up the delta was probably derived from outside the Eberswalde Crater and subsequently transported by rivers into the crater:

  • The delta consists of one or two main river channels (left side) that split into many smaller channels,
  • Bifurcating channels form distinct lobes – there are at least 6 of these, where each lobe represents a specific period of delta formation.
  • Switching of delta lobes is common in terrestrial delta. Each lobe represents a period of sediment movement and deposition, in this case into the deep crater basin.  At a certain point in time, the channel will switch direction and begin to build a new lobe.
  • Each new lobe partly overlaps older lobes, such that the younger deposits appear to lie on top of older deposits.
  • The Lena Delta in Russia provides a nice analogue for the overall shape of channels, with some active parts of the delta (especially the centre-right) juxtaposed with less active segments.

The Eberswalde Delta has another remarkable set of structures.  Meander loops (opposite image), seemingly identical to those seen in meandering rivers on Earth, contain patterns of progressive channel movement.  The Martian meander channel loop was eventually cut off, perhaps forming an oxbow lake like its terrestrial counterpart.

Martian landforms like these are mostly found in regions assigned to the Noachian Period, a geological interval that extended from 4.1 to 3.7 billion years.  All the evidence (so far) points to a time when surface water was common as rivers, lakes, and possibly seas; groundwater can be added to this mix.  If this was the case, there must also have been water vapour in the atmosphere.  The surface must have been significantly warmer than the present frigid temperatures; water vapour probably provided some degree of greenhouse protection.  Overland flow of water also produced sediment, much of which ended up in impact craters and broad lowlands.


However, some extremely large outflow channels, such as the Kasei Valles formed sporadically during a later, generally drier and colder time known as the Hesperian Period (3.7 to 2.9 billion years).  This massive system of channels and canyons extends about 3000km from its source in the Tharsis volcanic region, and through about 4km of topographic relief. The overall form of the channels, plus more detailed images of flow-like structures within the channels, indicates possible catastrophic outbursts of humongous volumes of water.  One popular hypothesis to account for this involves massive volumes of frozen groundwater being released either during meteorite impact or volcanic activity and heating.

The comparison between Eberswalde Delta and Kasei Valles mega-floods is quite stark; the delta represents relatively continuous river flow over a long period of time, into a crater.  The Kasei Valles outflow formed almost instantly, driven by the forces of impact and directed away from the crater.

Scientific understanding of Martian geology will continue to evolve; some hypotheses will stand the test of experimental and observational rigour; others will become history.  Modern science has developed the technology to actually do the field work, albeit remotely.  Perhaps we shouldn’t be too hasty to consign Schiaparelli’s and Lowell’s ideas to the theatrically amusing; their observations and explanations were not without context. Keep in mind the possibility that another H.G. Wells may point a satirical finger at 21st century science.

NASA, ESA and other organizations have multiple sites to access imagery and general information on all space missions.  SEPM (Society for Sedimentary Research) also has a Special Publication (number 102; 2012) with 12 papers that describe aspects of sediments and sedimentary rocks on Mars.  The Introductory chapter by John Grotzinger and Ralph Milliken provides an excellent technical summary of the Martian sedimentary realm.







Among wine drinkers, the term Terroir can invoke glazed expressions, or in real enthusiasts an opportunity to wax lyrical about the provenance of their beverage.  The term is French, morphing from the word terre , the land, or earth.  It conveys a ‘sense of place’, the earth, the climate, and the culture of wine-making.  In other words, pretty well anything that contributes to a wine’s character.

Opinions vary about the real significance of terroir. For some, the cultural foundations are most important in a kind of philosophical, metaphysical way.  For others, it is the physical environment in which the grapes grow, are harvested, and finally turned into wine.  For the more cynical it is just a marketing ploy, something to make the purchaser and imbiber feel good.  The French have honed this to a fine art, to the point where only wine from Burgundy can be called Burgundy, or Champagne from a region and appellation of the same name in north France. Continue reading