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On a recent trip to Flamborough Head I found myself both at home and somewhat disconcerted. Flamborough Head is made of chalk, very white and with all the fossils you would expect to find from the Cretaceous Period. Chalk is what I was brought up on. The water that came out of our taps came from an artesian well and had been filtered through chalk. Below the London Clay that made our garden impossibly claggy to dig, there lay a massive saucer of chalk cupping the clays, sands and river terraces which underpinned the London Basin. Less than 10 miles away southwards the chalk emerges as the North Downs, forming the massive pediment of a worn away arch – the other half of which is the South Downs. The Downs, North and South, were my escape – Box Hill and Beachy Head, Hope Gap and the Silent Pool all beautiful places to be as well as offering up a rich array of fossils. Inoceramus liabatus, Spondylus spinosus, Echinocorys scutata, Micraster cortestudinarium and Sporadoscinia aclyonoides were all happily collected and labelled as a teenage buff.

Why then, the Flamborough fluster? Part of it was being in the north when I’m used to going south of London to see chalk. But that shouldn’t really be a surprise as it is well known to me that the chalk outcrops that forms the anticline of the Weald (framed by the North and South Downs) is mirrored by a syncline which emerges the other side of London. After all I lived in St Albans for many years and regularly visit a musical retreat perched above the Hughenden Valley in the Chilterns and know of their chalkiness. These chalklands are part of a great arc stretching from Salisbury through the Chilterns curving north to just east of the Wash and reaching the sea between Kelling and Hunstanton in Norfolk. The chalklands then continue north of the Wash from Skegness right the way up the coast to Flamborough where they once again rise to make cliff scenery nearly as flamboyant as that around Beachy Head.

There were two other things at Flamborough which shifted my pre-conceived notions of chalk and were probably the cause of my disconcert.

Not long after we arrived in our lodging in Bempton, my partner Rachael asked in surprise, if the house opposite was built of chalk, commenting that it didn’t seem to be a plan to build a house out of chalk as it is so soft. I muttered about Chalk Rock and Melbourn Rock, bands of harder chalk within the southern, generally soft chalk, which are used as building materials. I was however surprised to see how many of the older buildings were made of chalk – it seems that northern chalk is, in general, harder than southern chalk.

I was also surprised that the only other common traditional building material was brick. I remember from the chalklands in each of Surrey and Sussex, Hertfordshire and Hampshire, Suffolk and Norfolk, that many of the older buildings frequently featured flints.

Flints make for beautiful looking houses. They are, however, a challenge for the builders as flint is so hard, fiercely sharp when broken and comes in irregular lumps. The history of flint as a building material goes back at least to Roman times. Whilst it is not an easy building material to use, it is extremely durable and freely available (at least in the southern chalk). Having observed and considered the sandstones used to build Hadrian’s Wall, it was fascinating to return to St Albans in February of last year, moments before the pandemic kicked in. Walking from Waitrose (an essential in St Albans) south into Verulam Park towards the Abbey, the path is bordered on your left by a Roman Wall. It is this which featured as Mystery Rock number 20 for the Hadrian’s Wall Community Archaeology Project. It is constructed from a mixture of brick and flint.

The Romans recognized that to make stable walls out of flint it is more effective to mix it with layers of rectilinear material. As with Hadrian’s Wall the Romans once again show their ability to choose materials and build with them to produce remarkably durable structures. Continuing down the hill to the River Ver and then up to the Abbey also allowed for an exploration of the complex built history of the Abbey. This provided another lovely, but very different, example of stone reuse. Significant portions of the transept and the northern wall of the nave are made of reused Roman material. Other walls in both the transept and the southern nave feature newer knapped flint used in much larger faces supported by stone quoins. This reuse matches the way that Roman stone is reused in medieval churches in the Tyne valley except that the materials being reused are very different.

Back in Flamborough we headed out to the coast and found that the absence of flint in the buildings is reflected in an absence of flint in the cliffs. We started our exploration on the beach at South Landing, just south of Flamborough and headed towards Danes Dyke and Bridlington to the west. Here it also dawned on me there was another major difference. The wave-washed cobbles between the chalk boulders by the cliffs consisted of a curious mix of Carboniferous, Jurassic and even older rocks, none of which occur locally. Looking up at the cliffs the reason is clear, with a 10m plus band of boulder clay topping the cliffs. These wave-washed cobbles had hitched a lift on a glacier and were dumped within the boulder clay as the ice departed (some 12 thousand years ago), and now the ice-transported contents are eroding into the North Sea. This ice-sheet didn’t reach Sussex, so the cliff tops at Beachy Head just have a thin layer of chalky soil, and the beach cobbles are exclusively flint (with the odd bit of brick where a house has fallen in). Further exploration of the coast at Flamborough Head and Thornwick Bay, revealed that there were some flints to be found, but different in character from those further south. These flints were grey and not clearly distinguishable from the chalk. At Birling Gap in Sussex the layers of flint nodules band the cliff in dark black, contrasting with the brilliant white of the cliffs. Individual nodules when broken are a beautiful shiny translucent black and have a rind of a porous mixture of flint and chalk.

Back home, reflecting on the trip to Flamborough, I was reminded once again of my university tutor, Professor Harold Reading, and one of his sayings; a geologist is only as good as the number of rocks they have seen. I’m certainly seeing chalk differently thanks to our visit to Flamborough.  Maybe it’s time now to plan trips to the Cap Blanc Nez and then to the Jasmund National Park in Germany and Møns Klint in Denmark, chalklands all. There are also chalk deposits in north America, Australia and Egypt. Apparently, the Champagne region of France is underlain by chalk too – chalk and cheese (and a little wine), now there’s a thought!

@Northumbrianman

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It was like walking in snow, except that we were surrounded by leafy trees in bright summer sunshine and 20 degrees of heat. The creamy white crystals that were reflecting so much light were not the pretty hexagons of ice-crystals but the rhombohedra of calcite. The drift of material we were intent on searching stuck out like a huge tongue between the wooded hillsides, pointing towards the wonderfully named village of Snailbeach in Shropshire. Lichens and moss, mares-tails, stonecrop, cinquefoil, willowherb and even small trees were starting to colonise the bottom edges of the mound where more water collected. Despite this and the surrounding borderland idyll the mine waste maintained a zone of lifeless desolation even 20 years after the mine’s closure in 1955. For my geo-pal Kevin and I, though, it was a world of excitement. We were here on a cycling holiday, or rather a collecting trip which involved some cycling and camping. Along with hunting for trilobites in the county’s famous Silurian and Ordovician outcrops, we were exploring the lead and zinc mining industry of Shropshire to see what beautiful specimens we could find in the disused mine-tips. We were also teenagers, away from home and relishing the freedom that this gave.

In amongst these old tips, it was still possible to find some fine specimens. Along with the brilliant crystals of quartz and the milky crystals of calcite, there were deep brown crystals of sphalerite. Sphalerite (zinc sulphide) is one of the main ores of zinc and valuable in its own right, as zinc is used as an alloy with lead to make solder and with copper to make brass. The name sphalerite and its alternative, blende or zinc blende both refer to sphalerite’s similarities with another ore mineral, galena. To Kevin and I galena was the prize, it felt fabulously dense in the hand and formed beautiful octagonal and cubic crystals which glittered in seductive greys. Galena (lead sulphide) is the principal ore of lead and for early miners sphalerite was a distraction from this valuable lead ore. The name sphalerite come from the Greek word Sphaleros meaning treacherous and Blende come from the German word Blenden to deceive. Clearly the word-coining miners were not happy about Zinc Sulphide.

It is curious that the Romans, who knew about zinc and its use in making brass, don’t appear to have mined the copious amount of zinc available in deposits in Britain. They did however know about the lead and mined large quantities of it exporting it all over the Roman Empire. It seems likely that lead (along with iron, tin, copper and gold) is what drew the Romans to Britain and encouraged them to make it part of the Roman empire. Lead mining started soon after the invasion of Britain with evidence of workings at Charterhouse in the Mendips as early as 49AD. This became a highly organised and productive set of open cast workings which by 70AD had overtaken the lead-mines of Iberia as the principal source of lead for the Empire. There is also a good fictional account of this mine in Lindsey Davis’ book “The Silver Pigs” which gives a real sense of the conditions in which mining took place along with some enjoyable speculations on the political and economic intrigue that may have surrounded such a valuable resource.

Lead is not only very dense but is malleable, durable and waterproof. The Romans understood this, and it was used principally to make pipes to carry water and for lining aqueducts, and also to make pewter plates and coinage. Galena itself (along with stibnite, an ore of antimony) was crushed to a fine paste to make khol which was used as an eye cosmetic. Some Romans also understood that lead was not good for their health. Vetruvius wrote in the 1^st century BCE: “Water conducted through earthen pipes is more wholesome than that through lead; indeed that conveyed in lead must be injurious… This may be verified by observing the workers in lead, who are of a pallid colour; for in casting lead, the fumes from it fixing on the different members, and daily burning them, destroy the vigour of the blood; water should therefore on no account be conducted in leaden pipes if we are desirous that it should be wholesome.” (VIII.6.10-11)

Pliny on the other hand, writing in the 1^st Century CE, noted that “Fresh hogs’ lard, applied as a pessary, imparts nutriment to the infant in the womb, and prevents abortion. Mixed with white lead or litharge, it restores scars to their natural colour” (Book 28: Remedies).  He also advocates that lead could be used as a liniment, or as an ingredient in plasters for ulcers and the eyes, among other health applications. As an aside this underscores that Pliny’s Natural History along with useful direct observation has a great deal that is unverified anecdote. For example: “Sneezing, provoked by a feather, relieves heaviness in the head; it is said too, that to touch the nostrils of a mule with the lips, will arrest sneezing and hiccup” (Book 28: Remedies, Chapter 15), and “For patients affected with melancholy, calves’ dung, boiled in wine, is a very useful remedy.” (Book 28: Remedies, Chapter 67). Taking this into consideration, his common appellation as a scientist does the meaning of science no favours. On the other hand, his detailed records of methods used in mining, extracting and refining metals are valuable resources in understanding what the Romans were making and how they did it.

Pliny gives detailed descriptions of the way that lead is extracted from its ore, galena. From this and other sources we know that lead, despite its value, was a by-product. Galena commonly contains a small fraction of silver, up to 0.5%, making silver the ore’s most valuable component. In writing this article I found a derivation for galena as “From Latin galena – “dross from smelting lead”” – it is a nice idea which I have been unable to verify.

For the Romans silver was not only used for high status ornaments and tableware but was the fundamental currency for the empire. We know from Pliny that the process used to extract the silver was cupellation. Lead melts at a relatively low temperature (327^oC ) whereas silver melts at 960^oC. When heated to circa 1000^oC lead will oxidise to form litharge (PbO) which can be absorbed into a porous calcareous material such as bone ash, leaving the now molten silver fraction. Typically, the bone ash was formed into a truncated cone shaped vessel; a cupel. The litharge having been absorbed would leave drops of silver at the base of the cupel. Later, the lead would be recovered from the cupel by re-smelting and the lead would be formed into an ingot, or pig, each weighing approximately 69kg.

The Romans’ quest for silver and lead in Britain was not confined to the Mendips. Roman lead mining has been identified in Wharfedale and not far from Hadrian’s Wall at Alston Moor. A Roman pig of lead was also discovered not far from the mine at Snailbeach making it another likely location for Roman lead/silver mining and extraction. All of this I neither knew nor cared about on my teenage visit, I was simply happy to have found some beautiful mineral specimens. Mystery rock number 19 for the Hadrian’s Wall Archaeology Project is one of the specimens that came back from that trip… and finding it would have been a good reason to head, once more, to the Stiperstones Inn.

Attributions and References

References:

Roman Lead Working in Britain. R F Tylecote (1964). British Journal for the History of Science vol.2 no.5.

Attributions:

Shropshire view: from http://www.shropshiresgreatoutdoors.co.uk/site/snailbeach-mine/

Galena: Galena with some golden colored pyrite (3.5 × 2.5 × 2.0 cm) from Huanzala mine, Huallanca, Bolognesi, Ancash, Peru. Ivar Leidus, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.

Lead pipe: By &lt;a href=&quot;https://en.wikipedia.org/wiki/User:Solipsist&quot; class=&quot;extiw&quot; title=&quot;en:User:Solipsist&quot;&gt;Andrew Dunn&lt;/a&gt; – &lt;span class=&quot;int-own-work&quot;&gt;Self-photographed&lt;/span&gt;, <a href=”https://creativecommons.org/licenses/by-sa/2.0″ title=”Creative Commons Attribution-Share Alike 2.0″>CC BY-SA 2.0</a>, <a href=”https://commons.wikimedia.org/w/index.php?curid=606468″>Link</a>

Lead Pig: British Museum. https://www.britishmuseum.org/collection/object/H_1856-0626-1

Sciapod from Pliny’s Historia Naturalae: By Michel Wolgemut, Wilhelm Pleydenwurff (Text: Hartmann Schedel) – http://www.beloit.edu/~nurember/book/images/Miscellaneous/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=490581

@Northumbrianman

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The first time I went to Wales we took a ferry from Aust on the east and English bank of the Severn to Beachly on the west and Welsh side. The next time I went to Wales we drove across the Severn Bridge with barely a glance at Aust a way down below us. I wish I had known then that the nearby cliffs at Aust form a famous exposure of the Rhaetic bone bed – I would definitely have been on the case with Mum and Dad. It wasn’t until several years later, in my teens, through exploring beds of the same age at Blue Anchor (not far from Minehead in Somerset and the home of my grandparents) and a trip to Aust with my old pal and co-geology nerd Kevin that I go to know and see what it was about. Till that point fossils had been about invertebrates – devil’s toenails (gryphaea), crinoids, corals, ammonites and trilobites. Vertebrates were a whole new layer of excitement and in these bone beds there was plenty to get excited about. Fish scales and ichthyosaur teeth and occasionally a piece of plesiosaur vertebra. These fossils have a different look and feel to them, preserved in phosphate minerals rather than carbonates and oxides and they had dark shiny surfaces, particularly the fish scales. Beneath their surface the bones had a distinctive spotty texture revealing a vascular structure where the blood vessels feeding bone growth would have been.

Another few years later whilst on a holiday in Minehead as an older teenager, I borrowed my Nan’s Moulton style bike, with its tiny fat wheels. I headed off for several days exploring the coast, blissfully in control of my own plans, staying in the youth hostel at Quantoxhead. On the last day of my planned trip whilst nosing around in the layered limestone-and-shale cliffs at Kilve Beach, I spotted a ring of material about 6 inches across which had this spotty, vascular texture in it. It was a large piece of bone and in a shape that suggested the snout of a skull. I spent the whole of the rest of the day excavating chasing the bone back into the cliff. The more I dug the larger it got! Late in the afternoon I realized I wasn’t going to get back to Minehead at the agreed time, so found a phone box and called to let my folks know that I was ok, but that I had found a dinosaur and needed a bit more time and a lift. It was later identified as likely belonging to an Ichthyosaur. This chunk of skull is now somewhere in the Oxford Museum of Science, still awaiting preparation even after 40 years in residence. Having recently indulged myself by purchasing an air scribe (the fossil preparation tool of choice) I am now considering the possibility of repatriating the skull to do the work on it myself.

This fossil was from the Lias, the oldest formation of the Jurassic period and at about 200 million years old is approximately 100-140 million years younger than the fossils to be found in the Carboniferous of the Northumberland Coast and the central and eastern part of Hadrian’s Wall. In the Carboniferous Period ammonites and dinosaurs, for which the Jurassic is famed, were in the distant future. The ammonites’ ancestors were there in the shape of goniates. These were spiraled like ammonites, but with much simpler suture lines marking out the division between their floatation chambers as has been explored in my earlier blog “Suckered”.  As for the vertebrates, the Carboniferous precursors of the dinosaurs had made it onto land in the shape of the very first amphibians: this is another story for another blog entry. The other vertebrates that were there were the fishes.

When I started writing this blog, I had intended to map out the evolution of fish. However, it became clear that this would involve writing a book; so here is a quick leap through some of the highlights.

Hag fishes are strange creatures with loose skin and an ability to produce prodigious amounts of slime which combine to make them very difficult to eat. The hagfish and the parasitic lampreys belong to the same class of fish, the Agnatha or jawless fish, which were the first to evolve. The jawless fish arrived early in the evolutionary history of multicellular creatures, appearing at the outset of the Cambrian Period at about 530 million years ago. These were simpler creatures than their distant modern relatives, probably filter feeders and with a notochord (like that found in an embryo) a rod like precursor to the development of vertebrae.

Fish with true vertebrae evolved later in the Cambrian period. Still part of the jawless fish family, they included armoured fish, (Ostracoderms) and Conodonts. The latter are small eel-like creatures previously know only for their teeth-like structures and highly valued as zone-fossils. It is from the Ostracoderms that an evolutionary line can be traced to the first jawed fishes (the epic Placoderms) and then to the explosion of fish types that marked the end of the Silurian and the beginning of the Devonian Period.

These new fish groups included the now extinct spiny sharks (Aconthodii), the cartilaginous fish (Chondrichthyes) which includes sharks and rays, and the bony fishes (Osteichthyes). The bony fish further evolved at this time into the ray-finned fishes (Actinopterygii) and the lobe-finned fishes (Sarcopterygii). We are familiar with the lobe finned fishes in the shape of Coelacanths which were thought to have become extinct in the Cretaceous but in 1938 were discovered living in the Indian Ocean. It is from the lobe-finned fishes that the first tetrapods, the early amphibians, evolved. The ray-finned fishes are even more familiar in the shape of haddock, mackerel, piranhas and goldfish amongst many others.

Having leapt through the evolution of fish, let’s go back to the beautiful foreshore at Cocklawburn Beach just south of Berwick-upon-Tweed, where rocks of the mid-Carboniferous Period are exposed. Not long after I first moved to this part of the world, I was exploring the limestone skerrs at Cocklawburn and was surprised to come across the very same shiny phosphatic bony material with the spotty vascular interior that I had noticed so many years ago at Kilve Beach. This is mystery rock number 18 for the Hadrian’s Wall Community Archaeology Project. It had something of the shape of a shoulder blade about it but about 12 inches across. I also noticed that nearby there were several square cuts in the rock where small slabs of rock had been removed with a saw.  Enquiry revealed that a (then) teenager, Max (who happened to be the son of Mick Manning and Britta Granstrom, then our neighbours and well known as a children’’ author, and illustrator and artist respectively) had made a discovery. The piece of bone was the last piece of this discovery, unnoticed or left behind for some reason, the rest having been collected by the Hancock Museum with permission from the Northumberland Coast AONB partnership. The find has been identified as the remains of a Rhizodont fish, a now extinct member of the lobe-finned class of fish. The remaining bone gives a clue to the size of this creature. As part of what would evolve into a shoulder this implies that this fish was many metres long. The Rhizodonts were predatory fish with vicious teeth so this would not have been a good fish to be swimming with.

The surge of excitement when I found the Icthyosaur skull remains vivid in my mind and finding the bone at Cocklawburn reminded me of that time. I imagine Max may have experienced that excitement too and I know many geologists who retain this feeling, and whilst some of them are paid-up professional geologists many of them are amateurs. The world of geological discovery is there for all, and for the young this maybe the beginning of a lifelong fascination.

Attributions

Aust Ferry: By Adrian Pingstone – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4095255

Goniatite: CeCILL, https://commons.wikimedia.org/w/index.php?curid=64362

Fish evolution diagram: By Epipelagic – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=24336974

Hagfish from: https://phys.org/news/2011-03-hagfish-skin.html

Lamprey mouth from:https://www.washington.edu/news/2009/07/23/ancient-sea-lamprey-dramatically-transforms-its-genome/

@Northumbrianman

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Swimming pools are not really the best place to appreciate an earthquake. I was enjoying the benefits of Iceland’s geothermal heat in an open-air swimming pool on the only occasion I have been somewhere when an earthquake took place in that location, and I only discovered it had happened when I was told about it afterwards. Iceland, situated on a constructive plate margin, is tectonically active and earthquakes are not uncommon. They do, however, tend to be rather lower down on the Richter scale, in a way that might make it possible to appreciate an earthquake rather than being terrified by it.  Constructive plate margins are in tension and are located where the crust is already thin (particularly in oceanic crust) or where the crust is in the process of being thinned. In consequence it is possible for the tension to be released more incrementally (unlike compression where long periods of oh-so-quiet suddenly become oh-so-loud and very destructive). Not to say that incremental tension release doesn’t cause problems. The Icelandic attempts at harnessing geothermal energy from the very high heat flows encountered on the island have been severely hampered by the water circulation pipes being bent and broken by earth movement. Expensive and costly but not deadly. The earthquakes can however be a signal of something more deadly about to happen. An increase in earthquake activity is a sign that magma is on the move and therefore a helpful predictor of imminent volcanic eruption.

In contrast to Iceland’s constructive margin earthquake experience, that of a destructive plate margin is altogether more devastating. Destructive plate margins are so named because a slab of oceanic crust and lithospheric mantle (solid) are diving back down into the aesthenospheric mantle (fluid and deeper), dragging its trailing plate behind it. It could equally well be called a destructive plate margin for the naked violence of its volcanic eruptions and its earthquakes. Mount Tambora and Krakatoa in Indonesia, Mount Pele in Martinique, Nevada del Ruiz in Columbia and Santorini in Greece top the list for human casualties, and all are found on destructive plate margins. The same is true for the most devastating earthquakes. Tangshan and Sichaun in China, Haiti, Peru, Kashmir and the Indian Ocean earthquake centered just of the coast of Sumatra top the location-list of recent deadly earthquakes. With fatalities in the hundreds-of-thousands, earthquakes are more deadly than volcanoes. The cost is devastating in so many ways. Not only in terms of in human lives and injury, but also the misery caused by destruction of homes and businesses and infrastructure resulting in loss of income, famine and illness. There are several physical factors that dictate the scale of damage. The amount of energy released by the earthquake (its magnitude) is the principal measure of how much direct damage an earthquake may cause through shaking and ground rupture. Landslides, lahars (mud flows), flooding and liquefaction of soils and unconsolidated sediments are also direct consequences of earthquakes. Additionally, earthquakes may cause tsunamis. I vividly recollect the news and images from Indonesia and Japan on Boxing Day of 2004 showing the astonishing devastation caused by this earthquake-induced tsunami and the consequent tragedies that followed.

It may seem from this that Earthquakes are literally the great levellers, indiscriminate in who and what gets destroyed. As individuals and societies, we do however have knowledge and experience both of where earthquakes are likely to happen and what can be done to mitigate the consequences when an earthquake hits. There are two places I have visited which illustrate this well. The first is San Francisco. I’m not a great lover of any city, but San Francisco is one of my favourites, with its vibrant mix of peoples and its beautiful setting, wrapped around by San Francisco Bay and the Pacific Ocean and its many hills providing beautiful vistas. It is however a city in peril, located as it is on the San Andreas fault, a 1200km-long active transform-fault. The southwestern part of San Francisco is moving north, and the northeastern part is moving south: intermittently and violently. After the devastating 1906 earthquake in San Francisco, much work was done to make buildings and infrastructure more resilient to earthquakes, with good effect. These words from the bible come to mind:

“Therefore whoever hears these sayings of Mine, and does them, I will liken him to a wise man who built his house on the rock: and the rain descended, the floods came, and the winds blew and beat on that house; and it did not fall, for it was founded on the rock.

“But everyone who hears these sayings of Mine, and does not do them, will be like a foolish man who built his house on the sand: and the rain descended, the floods came, and the winds blew and beat on that house; and it fell. And great was its fall.” (Matthew 7:24-27)

However, wise government and judicious engineering is not enough. The central, hilly part of San Francisco is indeed founded on rock, a good place to build not only for rain, but also for earthquakes which have less effect on rock. In contrast the estuarine deposits which fringe the bay area and recent alluvial deposits (sand!) are susceptible to liquification during an earthquake, indeed causing much greater damage. The choices to build and live in these areas are not so much about wisdom versus foolishness as economic necessity. The suburbs built on these soft deposits tend to be the poorest areas in the city. If your house is more likely to be destroyed by an earthquake in an area where earthquakes are inevitable, insurance becomes more expensive and the value of your real estate drops.

In contrast to San Francisco (wealthy albeit with a significant underclass within one of the wealthiest nations) Kathmandu is poor. Nepal is the second poorest nation in Asia. This fact can be attributed to political instability and corruption. I stayed in the Kathmandu valley when I visited Nepal in 2011. We stayed in a lodging house delightfully located in the centre of Bhaktapur. This wonderfully preserved ancient city with its temples and courtyards made of wood, stone, brick and metal is designated as a World Heritage Site.  4 years later, in April 2015, a massive earthquake struck, with an epicentre near to Gorkha to the NE of Kathmandu. The effect of this earthquake was amplified in Kathmandu, Patan and Bhaktapur as they are built on a basin of lake sediments. As distressing as the images were of these ancient temples reduced to rubble it only remains symbolic of what the Nepali people went through, with nearly 9000 killed and nearly 22,000 injured. Nabraj, who had been my guide when in Pokhara, had his family home near to Gorkha. Mercifully his family all survived, but sadly his village was all but wiped out. With no insurance and no government help, rebuilding was a major challenge, with his income from tourism also reduced to rubble.

With so many confounding factors it is apparent that earthquakes scoring highest on the Richter Scale don’t necessarily bring the biggest death toll. Population density, poverty and politics have a strong influence too. These are large and seemingly intractable problems, however as a geologist I would suggest that one of the ways to help with this is to understand how earthquakes work so that engineering and socio-political solutions may be put in place.

This takes us, via a few thousand miles and through 340 million years of history to mystery rock number 17 for the Hadrian’s Wall Community Archaeology Project. It is an example of fault gouge, the material which is produced when rocks fracture and move past each other. This fault is part of a fault complex to be found on the Northumberland coast at Howick and is likely to have formed as this Carboniferous sedimentary basin developed. Faults are responsible for earthquakes. On the Howick fault, there has been a total of about 40m of movement, compared to 3m of movement on the fault plane which created the Nepal earthquake. The fault plane at Howick is likely to be much smaller than that in Nepal, which means that each metre of movement on the Howick fault would have generated less energy than each metre on the Nepal fault.  Additionally, this total of 40m would have been made through many much smaller movements spread over many millions of years. Given that this fault developed under crustal tension it would have created relatively low energy earthquakes.

The early Carboniferous period (in which these rocks formed) would have been home to many creatures including some of the earliest amphibians. I like to think that, like me, these creatures may have failed to appreciate these earthquakes as I did in my geothermal swimming pool in Iceland.

Attributions

Hekla eruption, February 2000. Photo by: Iceland monitor/Rax

Village on the coast of Sumatra: U.S. Navy photo by Photographer’s Mate 2nd Class Philip A. McDaniel, Public domain, via Wikimedia Commons

@Northumbrianman

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Pottery kilns are greedy for power, so in preparation for installing a large second-hand kiln, I had a three-phase supply installed. This required cutting through a concrete path to make a trench and, when the cable had been laid, remaking the concrete path. It was the first big concreting project I had ever done, so when I had finished it, I neatly wrote the names of the people who had helped make it, including my older son Craig, along with the date.  It maybe that in a few hundred million years a geologist, of a highly evolved rat species, will unearth this concrete patch and use it as evidence in a paper on the ritual behaviour of primitive hominids in relationship to concrete structures.

If that writing is preserved over the millennia, it will have become a fossil. A particular sort of fossil.

When I hear the word fossil, the immediate images that come to mind are of ammonites, crinoids, shepherd’s crowns, trilobites and corals. Dinosaurs come to mind too, massive bones, lines of vertebrae, teeth and horns. These are the remains of the actual creature, usually their hard parts and often with their skeletons or shells replaced by a different mineral. The soft parts of an animal are rarely preserved, requiring an exceptional combination of speed of burial and environmental chemistry. Without this the remains would be predated, physically broken up, decayed, oxidized or dissolved. When this intersection of favorable circumstance does happen, it results in fossils which are amazing and tell us so much more about the animals – for example the recent discoveries in China of feathers on a number of dinosaur fossils.

For most ancient creatures, the information we have about their cells, muscles, nerves, brains, hearing, seeing and so on can only be inferred from the hard parts to which they attach or within which they are contained.  We can measure skull cavity sizes to infer brain size, bone size and density along with muscle attachment points to work on musculature. We can also see the gas chambers and siphuncle of ammonites which tell us a bit about their flotation mechanism. We can also put these ammonites into a flume to see how water-dynamic their shapes are and infer something of how well adapted they are for moving.

All of these things are fascinating and help build a picture of what these animals were like and what they were capable of.  What they don’t tell us is what they actually did. If Hamlet had looked at Yorick’s skull without knowing him well, alas he would not have been able to say anything of his infinite jest.

For ancient creatures, there is however, another type of fossil which helps us understand more of what these animals actually did. These are trace fossils, and ichnology is an important branch of paleontology which not only tells us what animals did, but also provides another set of diagnostic information which helps us understand the environment in which they are preserved.

The most obvious of trace fossils are footprints and trackways. Some of these even make an appearance in Roman remains. Just like my writing in the drying cement, there are some tiles at an undisclosed site where the paw prints of a dog can be found. Whether this is a particular dog that likes the feel of clay, or a potter’s dog that the owner wanted immortalized or whether potteries were particularly dog-rich environments is not clear. It simply tells us that dogs were around and dipping their paws where they probably weren’t welcome!

Fossil footprints and trackways are not uncommon, with dinosaur footprints making news in recent years with discoveries in the Jurassic strata on the Isle of Skye as well as in the Cretaceous rocks of the Isle of Wight. More locally, tracks discovered by Maurice Tucker, have been found in the lower Carboniferous rocks at Howick on the Northumberland coast. These proved to be from an early amphibian, probably from the Temnospondyl group and are one of the oldest amphibian footprints ever found.

Not all trace fossils are so obvious or so glamorous. Many of them are simply burrows or feeding trails and unlike the footprints, it is often hard to work out what animal made them. This is in part because many burrowing animals only consist of soft parts, so that what they did in chewing their way through soft sediment is the only record of their existence. This reminds me of a lecture we had at college from Professor Jim Kennedy on early molluscan evolution and their development to manage the relative positions of mouth and anus in their simple guts. My recollection is that Jim said something along the lines of, “much of their evolutionary effort was directed at working out how not to crap on their own heads”. This seems like a hard almost futile existence, but evolution is nothing if not a long game!

The rocks of the Carboniferous Period in Northumberland and beyond have a rich variety of trace fossils preserved within its many kilometers of deltaic and marine limestones. This month’s mystery rock, number 16 in a series, is one of them. This particular gem comes from the geologically fabulous Cocklawburn Beach just south of Berwick upon Tweed. Until very recently I had thought that these beautiful three-dimensional patterns in these siltstones glorified in the name of Eione monilforme. However, in trying to discover what sort of creature made these remarkable traces, my learned colleagues pointed me towards a paper in which they have acquired the even more remarkable name of Neoeione monilforme. It is a shame that scrabble doesn’t allow proper names! As far as the animal is concerned, I quote from Dr Katie Strang’s reply (an expert on all things Carboniferous – particularly sharks) “It was originally thought to be made by a mollusc, but has now been attributed to a deposit-feeding endobenthic (ie a lived in sediment at the lowest level in a lake or the sea) worm-like animal, that actively back-filled its burrow, but…”. As with many things geological, there is clearly still room for speculation, debate and further observation…

…and maybe this is a fitting sentiment to end this piece. My concrete scribblings have lasted all of 10 years so far and maybe some of the pots that were made in the kiln will appear, at some distant point in the future, in a Raturnine archaeological trench as a definitive marker for the late Anthropocene.

Attributions

Iguanodon footprint along the foreshore at Compton Bay.from https://ukfossils.co.uk/2016/06/17/compton-bay/

Dinosaur footprint An Corran: from https://www.nature.scot/dinosaur-sites-skye-be-given-official-protection

Amphibian footprint from Howick: in David Scarboro and Maurice Tucker: “Amphibian footprints from the mid-Carboniferous of Northumberland, England: Sedimentological context, preservation and significance” Palaeogeography Palaeoclimatology Palaeoecology 113(2):335-34

@Northumbrianman

The post Who gives a fecal pellet? appeared first on WallCAP.

It may be that my memory is not quite right, but I have a strong recollection of visiting Ghiradelli Square Factory in San Francisco and being fascinated by the massive stone rollers grinding the chocolate to produce the beautifully smooth finished product. It was nearly 40 years ago, but I also have a recollection of the way that the chocolate was formed into beautiful folds against the bar at the bottom of the roller. The inexorable movement of the roller pulled the base of the viscous chocolate onwards while the bar held the top of the delicious smoothness in place. The rollers I am sure about, the ripples might just be in my imagination. A chocolate sundae and a sun-soaked view out over San Francisco Bay to Alcatraz and the Golden Gate Bridge after the event does do things to soften the memory.

It is a slightly tenuous, albeit irresistible analogy to make to describe the process which formed this month’s Mystery Rock for the Hadrian’s Wall Community Archaeology project.  Chocolate clearly isn’t magma, but both magma and chocolate are viscous liquids when heated albeit the magma is rather hotter than the chocolate. Basaltic magma is liquid at temperatures over 1000C and flows rapidly, as can be seen from the spectacular images coming from the current eruption at the Geldingadaler volcano in Iceland. What can also be seen from this eruption is the way that this magma becomes stickier as it cools from bright yellow heat to red heat to black. If the magma is continuing to move and the crust of cooling magma is kept hot enough that the surface doesn’t cool so much that it becomes brittle, then, just like the Ghiradelli chocolate, the cooling sticky lava will be pulled into ripples and braids which have a texture much like a coil of rope. As the top of the curve in the coils points along the direction that the underlying magma is flowing, ancient examples of ropy lava give useful evidence about the volcano from which it was erupted.

Mystery Rock 15 doesn’t come from a volcano though. This image was taken just north of Bamburgh Castle at Harkess Rocks at an exposure on the top of the Whin Sill. The shape and form of the ropy braids is unmistakable and the curve in the braids tells us how the magma was flowing. This all occurred under the ground, though, away from the cooling air which formed the ropy braids at Geldingadalir and in many other basaltic volcanoes. How could this have happened? The clue is in the curved outline of this small section of the Whin Sill which has this ropy texture. This whole process is contained within a gas bubble like a little world inside a very hot “snow globe”. Volatiles are a common component of magmas and the formation of gas bubbles a regular occurrence as the pressure on the magma is released as it reaches the surface. What is unusual is that the volatiles have come out of solution within the Whin Sill under the ground. This tells us that either the intrusion of the sill was close to the surface and/or there was a pressure release caused by the magma pulsing forward as it wedged its way between the layers of Carboniferous sedimentary rock. It is not surprising that this rare phenomenon is recorded as a significant point of interest within the series of Geological Conservation Reviews carried out to record the best of British geological exposures.

Just a short blog this month as there is so much fieldwork to organize. Maybe just a little time to visit the Doddington Milk Bar and enjoy one of their excellent chocolate sundaes whilst taking in a view of the Cheviots.

Attributions & Links

Chocolate Grinding: By Sanjay Acharya – Own work by uploader. Picture taken at Ghirardelli Square, San Francisco, California USA, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5178665

Alcatraz: By Centpacrr (talk) (Uploads) – Own work, CC BY-SA 3.0, https://en.wikipedia.org/w/index.php?curid=38140500

Ropy Lava: By Tari Noelani Mattox,[1] USGS geologist[2][3] – https://web.archive.org/web/20070102035046/http://volcanoes.usgs.gov/Products/Pglossary/pahoehoe_ropy.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=700082

Link to Geldingadalir ropy lava flow:

https://www.youtube.com/watch?v=aZenXClZn4U

@Northumbrianman

The post Old Rope appeared first on WallCAP.

The taxi drivers at Arughat Bazar wished to proclaim their faith with slogans emblazoned on their battered cars like “Jesus Dead For You” (sic). It could also be taken as a warning of what lay ahead on the narrow winding dirt roads with vertiginous drops of hundreds of feet to rocks strewn in the powder blue Budhi Gandaki River in the gorge below. This heart-stopping drive took us to the start of a 14-day hike around Manaslu in the Nepalese Himalayas. The Himalayas are a good place to learn new perspectives and to let go of preconceptions. The sheer scale of the place provides a cold and implacable sense of one’s place in the world.

This is a story I have already told in an earlier blog (“Scratching the Surface”) but it seems to me worth re-telling to set the scene for explaining this month’s WallCAP mystery rock. One of the (many) preconceptions I brought with me to Nepal was about glaciers. From the pictures I had seen I assumed that they would be snow-strewn and that in the crevasses you would be able to see icy layers turning deeper shades of blue. In preparation for the summit of the Manaslu Circuit at the Larkye La pass I had asked my guide, Roshan, about crampons, but he had said they wouldn’t be necessary. This puzzled me at the time, but he was oh so right.  There was some snow and some ice as we reached the pass just after sunrise, but the way was mostly covered in rock debris ranging in size from boulders to sand. This was in part because the bits of the glaciers we were walking on were at relatively low level in the zone where the argument between snowfall and melting is played out. It is however also to do with ice’s phenomenal ability to break up and move rock around.

Not only were the glacier surfaces we walked on covered in rock of all grain sizes, but around the margin of the glaciers were huge ridges of sediment. These marginal moraines were more prominent as the surface of the glacier was much lower than the moraine ridges. Each year the glacial tongue will extend during the colder months as more snow, compacting to ice, flows down the mountain side. As the seasons turn and the sun fights back against the ice, melting becomes faster than the ice flow. This annual argument is usually balanced, but now it is turning in favour of the warming climate and these glaciers are clearly in retreat, leaving behind massive piles of rock debris.

Mountain glaciers are impressive, not least for their mountainous setting, but they are not on the same scale as the polar ice sheets. Where the mountain glaciers measure in the tens of kilometers, even the relatively small ice sheets of Iceland measure in the hundreds.  Flying to San Francisco many years ago the view down to Greenland was clear and cloudless and we flew for hours across unbroken ice.

When thinking about the effect of ice on our landscape in the Hadrian’s Wall corridor, it is this sort of ice that would have been the cause of many of the landscape features we now see. The margins of Iceland’s icesheets as they retreat provide a good analogue for what we see here.

Ice is a powerful tool, and this is because of two things. The first, that within the normal temperature range on our planet it passes between a solid, a liquid and a gas. The second is that when it solidifies from a liquid, it expands. This is very unusual and has consequences. The first is that it operates like a natural crowbar. Water that infiltrates rock, when it freezes, will happily break open even the hardest of rock types. The second is that it floats on top of its own liquid, water, rather than sinking. Without this feature ice-skating would never have become a thing and not only because of the skating-surface that ice forms as it floats. There is yet another feature, which is the way that ice responds to pressure. Usually, pressure will compact a solid so that it becomes more difficult to melt, however ice under pressure will tend to melt. This is what happens at the knife edge of skate-blades, where the intense pressure this causes against the ice results in the formation of a thin layer of water, lubricating the skater’s path. Without this, the steel blade would stick to the ice, and the skater’s glide would become a skater’s face-plant.

A similar principle applies to icesheets. There is a balance of pressure and temperature where the advance of the icesheet is enabled by a layer of water at its base. It is not only the ice-fractured rock which falls onto the ice which creates rock debris, but the water and ice underbelly of the glacier which grinds and flushes out the rock. We can see examples of this within the Hadrian’s Wall landscape, for example in one of the early WallCAP Mystery Rocks from near to Heavenfield. Here the surface of sandstone has been flattened and smoothed, and linear grooves have been raked into its surface, all by the action of ice.

What happens, then, when the ice melts? At the poles where ice flows out into the sea, as the ice melts, the rocks contained in the ice fall to the sea floor. These random stones are referred to as dropstones and can be seen in the arctic deep. They can also be found in the geological record and are one of the pieces of evidence used to show that there have been a few periods of the earth’s history where the entire planet has been glaciated – popularly named as Snowball Earth.

On land we can see the systematic remains of glacial action and retreat. Ground moraines and the drumlins that are created from them by the continued movement of the ice, scatter the landscape. Other features like eskers, and subglacial channels which have formed as a result of water-movement under the ice leave ridges and furrows in the landscape. As the ice retreats, the meltwater from the ice is added to the prevailing precipitation creating huge volumes of water. Sometimes this may be trapped by retreating ice to create lakes and consequent flat-lying lake deposits. This water also creates large high energy river channels which rework the glacial debris leaving behind meandering deposits, which often border contemporary rivers now much shrunk in size. Around Hadrian’s Wall this means that most of the landscape has a covering of one sort of glacial deposit or another.

Ice’s rock-moving super-power is manifested not only in the massive volumes of rock debris it creates, but also in the distance it moves this material and the incredible size of some of the boulders it drops into the landscape. One such boulder is the Loch Maben Stone which features as this month’s Mystery Rock for the WallCAP project. This huge, rounded stone is made of granite, a rock type which is foreign to the bedrock it overlies (the Triassic St Bees Sandstone). The nearest granite to the Loch Maben Stone is approximately 30km away, beyond Dumfries. Glacial erratics like this come in all sizes, but they have all wandered from their place of origin within a carpet of ice, hence the name erratic. Erratics weighing many thousands of tons have been recorded as well as pieces that have wandered for thousands of kilometers. On the Northumberland Coast It is possible to find a particularly characteristic volcanic rock, with elegant, elongated phenocrysts, which have travelled from Norway.  This means that the glacial ice not only walked 500 miles and walked 500 more but also walked on water for this stone to fall down on the Northumberland shore.

These erratics were one of the pieces of evidence that convinced Louis Agssiz, a Swiss geologist of the 19^th century, that there had been a past ice-age during which glaciers had extended all over Switzerland from the Alps and out into the plains of Europe. Working with William Buckland, the only person in Britain he could convince of his ideas, they looked for evidence of glaciation in Britain and concluded that all of Scotland and Ireland had been covered in ice.  These findings were published in 1840 in a 2-volume work “Études sur les glaciers”. This was a moment in the history of geology where pre-conceptions about past climate took a radical turn, providing a crucial piece of understanding to build our contemporary picture of climate change.

Back to more local concerns, it has been fascinating spending time at the recent Heritage at Risk dig undertaken by WallCAP at the Cambeck Crossing, the first this year with volunteers. Near to the trace of the wall, an area was uncovered containing cobbles which were probably sourced from the nearby riverbed in which there are sizable banks of water-worn cobbles. Examination of these cobbles shows them to be made of sandstones (including some distinctive poorly sorted grey sandstones which are likely to be turbidites), low grade metamorphosed sediments and granites. These are all erratics and likely to have been derived from the Ordovician and Silurian terranes and Devonian granites to the north west. I discussed the sequence of events that brought this about with the volunteers: the coming of the ice and how it levelled the landscape, leaving behind a rich variety of glacial erratics and how this material would have been re-worked by the rivers.  We also discussed how lifting the weight of the ice allowed the land surface to rise, like a super-tanker being unloaded, so that the Cambeck cut down through the glacial material and the soft sandstone underneath to create the gorge we now see. That our landscape, which seems set and permanent, can change so much in a relatively short time is remarkable and the role which climate change plays in this important. With the rate of man-made climate change exceeding that of the last ten thousand years what will be the consequent changes that we will see? It seems we have reached another moment in geological history where there is a need to revise our preconceptions and take action.

Attributions

Example of a glacial dropstone from Namibia, in rocks that date to the second Snowball Earth. The stone was likely carried and dropped by a floating ice shelf, and when it plunked into seafloor sediment below, that sediment folded around it. (Penny shown for scale.) Image by Paul Hoffman in: https://astronomy.com/news/2019/04/the-story-of-snowball-earth

@Northumbrianman

The post Snowdrops appeared first on WallCAP.

Bedtimes were strict when I was 11, so there was a going-on-holiday sense of excitement when we were woken in the early hours of the morning. Still drowsy, my older brother Steve and I were brought down to sit in front of the black and white television to watch the first man step out onto the moon’s surface. We had followed the whole mission on the BBC from the launch 5 days earlier and watched as the Lunar Excursion Module had separated from the Command Module on the evening of Sunday 20^th July 1969.   I can remember little of the BBC programme other than the air of excitement and the strange other worldly images that unfolded as Neil Armstrong made his famous small step speech as he bounced onto the moon’s surface. For an eleven-year-old me, the extraordinary achievement was merely what was happening in front of me, my normal. Now, I look back on the levels of danger involved, the near total vacuum and absolute zero emptiness of space, the solar radiation, the primitive computing technology, the nail-bitingly fine margin of fuel and the absolute hostility to life of the moon’s greyscale airless surface and I am amazed.

The rock samples brought back have been examined and analysed and we now know a great deal more about the ancient igneous surface of the moon and how it has been scarred by impacts. The favoured theory for its formation has the earth colliding with another smaller, Mars-sized planet named Theia about 4.5 billion years ago. Both planets had already accreted enough mass and heat to have differentiated into a metallic core and rocky mantle. The glancing impact resulted in a significant chunk of Theia’s core being dumped inside the earth with the remaining fragmented core and mantle material ejected to form a disc of material rotating around the earth. This fragments then accreted to form the moon with the multiple impacts generating so much heat that the surface of the moon down to a depth of maybe 500km became a magma ocean. The subsequent history of the moon is dominated by two processes. The first is a consequence of asteroid and comet impact, the results of which are an obvious feature of the cratered surface of the moon. The order in which impacts happen can be worked out from the way that ejecta from impacts overlap allowing for a timeline to be calculated for both the impacts and the features they interact with. The size and frequency of impacts has reduced significantly over time after a particularly intense phase known as the late heavy bombardment between 4 and 3.85 billion years ago. The second process is the progressive cooling of the moon with its magma ocean consequentially crystallising, with the heavier minerals (olivine, pyroxene) sinking and the lighter ones (plagioclase feldspar) floating, a process called fractionation. The paler grey uplands of the moon owe their colour to these lighter, feldspar rich fractionates. Volcanism is part of this process and vast amounts of magma (and some explosive pyroclastic material) flowed into lowlands on the nearside of the moon to form its “seas” cooling to form the dark basaltic plains of the moon’s Maria. Most of the Maria were formed between about 3 to 3.5 billion years ago but some volcanism may have carried on until about 1 billion years ago, 500 million years or so before multicellular life started to evolve on earth.

The moon is very different from the earth, it has no atmosphere, no magnetic field, no tectonics sufficient to rejuvenate its surface, very small amounts of water and no life. Yet there is a great deal we can learn from the moon’s geology to help understand the Earth’s pre-history. Not least is that early collision with Theia which tells us part of the story of the internal structure and geochemistry of our earth. The Moon’s collision-scarring tells another hidden part of the Earth’s past. The Earth’s tectonic activity means that the surface of our planet continues to be refreshed and reworked. The bombardment the moon suffered would have been equally inflicted on the Earth, however on Earth the scarring has since largely been erased. On a broader scale, our knowledge of the moon’s geology confirms and enrichens our understanding of the way that planets accrete and differentiate. The moon’s early history as a hot tectonically active planet before it cooled and died confirms and informs our knowledge of igneous processes.

50 years on from the Apollo moon landings, there have been no repeat performances. In the intervening time, humans have only ventured as far as the earth’s orbit. This underlines the achievement of the Apollo program not only technologically but also politically. It is only now with a much more robust baseline of technology, a firmer “foothold” in the Earth’s orbit and with the growing involvement of private enterprise that the prospect of manned exploration is in sight, this time to Mars.

Part of the reason for writing this blog now is the current attention on Mars as Perseverance, the  Mars rover and its sidekick the Insight helicopter send back yet more astonishing images of the planet. Mars has had quite a lot of attention from unmanned spacecraft in the years since Apollo, with orbiters and several landings with robotic exploring devices.

Mars has more affinity with Earth than the moon albeit doesn’t have the rather exotic collision and core-sharing co-history. Mars in common with the other rocky planets (Earth, Venus and Mercury) has a metallic core a rocky mantle and a crust. As it is larger than the moon its tectonic history stretches almost to the present albeit in its last throes. It still has an atmosphere, and this leads to the interaction between its atmosphere and Mars’ considerable topography. With lower gravity than the Earth, Mars has been unable to hang onto much of its atmosphere which has progressively spun-off into space, leaving a carbon dioxide remnant to kick up dust-devils. There was a time, however, when Mars’ atmosphere was more like that on Earth and there was free water and ice. What this means is that on Mars, we not only see the volcanic activity and the impact cratering but also an impressive range of sedimentary features.

One of the images for this month’s mystery rock for the WallCAP project is an example of this. We know from looking at terrestrial examples that when water or air transport sedimentary material, that they deposit that material in layers. Sometimes, when ripples or dunes are created these layers will be in the form of cross-lamination. The image on Mars was taken by the Curiosity rover and is of a rock outcrop named Mont Mercou which is located within Gale Crater on the slopes of Aeolis Mons (also called Mount Sharp). Aeolis Mons is thought to be the remnants of a large stack of layered sedimentary material. In the image of Mont Mercou you can see that it has two parts. The upper portion has cross-bedding in it, which is similar in form to that seen in the other image for this month’s WallCAP mystery rock. This is a picture of wind-blown, aeolian dune deposits from the Yellow Sands Formation at Tynemouth. The lower portion of Mont Mercou is a stack of horizontally laminated sediments which remind me of the layering which can be found in the sediments at Ladycross Quarry. The Martian deposits have been interpreted as lake deposits which progressively infilled Gale Crater after its formation between 3.8 and 3.5 billion years ago. To make these sorts of lake deposits would require the repeated, rhythmic influx of flowing water to bring the layers of coarser sediment into the lake. These coarser laminations are separated by thin bands of finer material which imply periods of limited water movement in which these finer grained sediments could settle out. There is an active debate about exactly what processes are reflected in the images being sent back from Mars and I am looking forward to following this story as more information becomes available and the debate continues.

The astonishing range of images and data which Curiosity, Ingenuity, Perseverance, Insight and their ilk are bringing us seems to have become my new normal. There is so much more that could and may well be explored not only within our nearest rocky neighbours but also out to the distant gas giants with their extraordinary moons as well as to the remote ice planets. Yet the long intermission of lockdown has also meant that my other new normal in the physical tangible world, the one that I can touch and see and smell and hear, has been focused down to what may be easily reached from North Northumberland. What is clear, is that I am not going to run out of interest between the local, tangible and touchable and the huge variety of what may be accessed via the low carbon format of the internet.

Acknowledgements and further information

You can follow Curiosity Rover on this interactive map here: https://mars.nasa.gov/msl/mission/where-is-the-rover/

Moon image by Gregory H. Revera – Own work, CC BY-SA 3.0, httpscommons.wikimedia.orgwindex.phpcurid=11901243

Vandelinus Crater: By James Stuby based on NASA image – Reprocessed Lunar Orbiter 4 image cropped in Adobe Photoshop to show Vandelinus crater and surrounding terrain. The original image should be public domain as it is a work of the U.S. Government (NASA). Immediate source: Lunar and Planetary Institute, Lunar Orbiter Photo GalleryLunar Orbiter 4, image 184, h1 [1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=30497934

Anorthosite: a coarsely-crystalline anorthosite from Labrador from the Ten Mile Bay Quarry, near the town of Nain along the Labrador coast, eastern Canada. The quarry exploits the Nain Anorthosite (Nain Plutonic Suite), a mid-Mesoproterozoic intrusion (1.29 to 1.35 billion years) emplaced along the Abloviak Shear Zone. https://commons.wikimedia.org/wiki/File:Blue_Eyes_Granite_(anorthosite)_Labrador.jpg

Barringer Crater Arizona: By National Map Seamless Server – NASA Earth Observatory, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7549781

Mont Mercou image edited by Kevin Gill: https://twitter.com/kevinmgill

Mars Image: By ESA & MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA, CC BY-SA IGO 3.0, CC BY-SA 3.0 igo, https://commons.wikimedia.org/w/index.php?curid=56489423

@Northumbrianman

The post Out of this World appeared first on WallCAP.

The brief guide to speaking Nepali lay open in front of me with a cup a coffee and cake in the Black and White Café in the main street of Pokhara. This was one of a number of eateries I patronised from many places which fed the appetites of the large tourist trade based on the town’s obvious charms.  Located on the shore of Phewa Tal it looked out over the lake to wooded hillsides in which the Peace Temple nestled behind the village of Anadu. When we had first arrived the view away from the lake was obscured by clouds, but during the afternoon they cleared and by sundown the unimaginably vast line of the Himalayan peaks around Annapurna, centered on Macupachere, were picked out in the distant dusty pink of the last rays of the sun.

I had been waiting to see if I could secure a permit to make the trek around Manaslu, a journey of about 14 days which would take me up to the high pass at Larkye La at 5216m. A lodge had just been opened which allowed for the whole circuit to be walked without the need for tents giving me access to an area which remained relatively uninfluenced by tourism in comparison with the trek I had just completed up to Annapurna base camp.

Languages really aren’t one of my strong points. My ability to retain foreign words seems frustratingly poor – I can hold onto the obscure latin names of long dead creatures from the Cambrian to the Eocene but remembering the words and order and pronunciation to ask for a coffee took forever. It was not just the words and syntax it was the whole social thing. I reckon myself to be extrovert in that I enjoy performance and find ideas spark most vividly when I am talking with others. However, my heritage is shy and introverted. The waiter in the Black and White café had been watching me from behind the bar came across and asked if I wanted another coffee. In doing so he also observed that he had seen me reading and re-reading the Nepali phrase guide, and why didn’t I just give it a go! He was so very right, the point of language is to interact and learning by doing is so fundamental, particularly with a language, any language, where the feel of it in your body and the response to it is what it is about.

This language-anxiety which has been a skein of thought though many of my travels came back to me whilst trying to work out how to communicate the complex language which is associated with geology. I find that once I have established the meaning of words associated with concepts in my mind, that I tend to forget that this may not be the case for others I am talking to. This is something my partner Rachael is good at reminding me of. A while ago we were doing some cooking together, on this occasion making a large crème brulee. I asked Rachael if she could pass the flan dish, the chosen receptacle for the crème brulee. In asking the question I had the whimsical notion, which I unwisely voiced, that flandish sounded like some sort of obscure language. Now, whenever my descriptions of geology flirt with the obscure, I will hear Rachael’s voice calls out “Flandish!” whether she is actually there or not (much in the same way Len Goodman delivers a Strictly Come Dancing “Seven”).

Along with comprehending vast amounts of time and thinking in at least three dimensions, geology’s mountainous conglomeration of words provide a challenge. There’s a lot of Greek and Latin – from the terrible lizards (dinosaurs) to the period of ancient life (the Palaeozoic) – and geologists like their legends too. The Titans (sons and daughters of the original gods of sky and earth, Uranus and Gaia) feature strongly in ocean naming. Iapetus for the Palaeozoic ocean crushed by the Caledonian Orogeny and father of Atlas after whom the Atlantic Ocean is named. Rhea and Tethys also have their own ancient oceans, Rhea being the mother of the Olympian gods and Tethys taking over from Thalassa as the primeval spirit of the sea. Thalassa herself features in the name of the Panthalasic ocean which surrounds the singular continent of Pangea during the Mesozoic era.

Discoverers’ and patrons’ names also make an appearance in fossil names alongside a mass of Greek and Latin descriptors. Dinosaur hunters seem particularly prone to giving out curious names such as Gasosaurus and Irritator with a prize to Bambiraptor feinbergi which combines Disney with patronage (literally the Bambi thief of the Feinbergs – the Feinbergs being the folk who bought the original specimen and lent it to the Graves Museum of Natural History in Florida).

Place names feature most strongly though, which is no surprise as rocks are anchored to place, particularly when naming occurrences of rocks in stratigraphy. The major periods of geological time are derived from understanding the relationships of major rock units and so several of their names feature places, for example the Devonian and Permian. For others of these major time units place has been related to tribe, with the Celtic tribes of the Silures and Ordovices now enshrined in the time periods of the Silurian and Ordovician. Places also feature in mineral names such as Cummingtonite (named after Cummington in Massachusetts) and my favourite the mineral Mullite named after my research area, the Isle of Mull.

There is a wealth of fascinating information bound up with the words used to name things in geology and there is potential for endless interest in unravelling these layers to help light-up the meaning of the geology.  It is however possible to get tied up in the words and unscrambling their meaning. Understanding the difference between a nonconformity, a disconformity, a misconformity, and an unconformity may have value as each has a very specific meaning (except for one which I made up*) – but they are only of value if they become part of the conversation and create real meaning, a deeper level of knowledge and understanding, self-expression, interest or some fun. For me, the most interesting thing is the way that the words and their meaning, and the conversation that flows from using them, helps to understand the geological processes that make our planet work. There are many other ways that the conversation can turn though, perhaps towards history or people, the language itself or simply getting to know each other.

To my shame I didn’t make much progress with Nepali, too many of the lovely Nepali people were good enough at speaking English and more than willing to do so. I had more success with the permit which came through after a few days and my host Nabraj found me an excellent guide, Roshan. As the trek progressed less English was spoken by the people we met, and the Nepali language was replaced by Tibetan as the primary language. The beautiful traditional greeting of “namaste” (I bow to you) was replaced by “tashi delek” (which translates approximately as “blessing upon you”). To find my way through not just the language but the culture and the practicalities of finding lodging Roshan was invaluable. He had a twinkle in his eye and with boyish good looks it seemed to be a feature of all the lodging houses I stayed in that they were invariably run by rather attractive young women.

It was through Roshan that conversations were started, and I learned more about this remarkable country: learned how hard the Nepali guides worked, many having worked abroad in places like Dubai as labourers in appalling conditions in the frequent times work was not available in Nepal; learned about the mule trains bringing in goods from China across the mountains and learned about the Buddhist stupas, mandalas and mani stones. It is the mani-stones which feature in this month’s mystery rock for the WallCAP project. Each stone has carved on it the Buddhist mantra Om Mane Padme Hum in Sanskrit. The creation of the stones, reciting or chanting the mantra or walking around the stones (to the left of the stones moving clockwise which Buddhist doctrine consider as the way the earth and the universe revolve) are all devotional activities. The mantra itself is symbolic of the pathway to enlightenment through perfecting each of the six practices of generosity, pure ethics, tolerance and patience, perseverance, concentration, and wisdom.  Many good reasons to have this written in stone, and also many good reasons why, as the waiter at the Black and White café observed, that joining the conversation is such a good thing. It also seems to me that there are times when a good guide is exactly what you need.

*Misconformity is not a geological term

@Northumbrianman

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Coming down the track were some local villagers. They were not the porters I had seen many times, often wearing flip-flops or bright purple wellies carrying cast iron pipes, water tanks, chickens and more. The porters tripped lightly with their massive loads, along the mountain trails which lead through the villages and monasteries around Manaslu up to the high passes of the Nepalese Himalayas and the border with China. These villagers were carrying slabs of stone on their backs, each slab many feet square, inches thick, made of the local metamorphic schists and used as roof tiles in the local houses.  A little further up the track a cluster of villagers gathered around large stacks of the roof slabs taking their turn to pick up a load to be moved down the valley. I enquired of my guide, Roshan, what the reason for the mass movement of roofing material was. He told me that the villagers had found that the mountainside above their village was unstable and was going to collapse imminently in a landslide that would bury the village. The villagers, without any external help, had simply taken their stone-built houses apart, moved them down the valley to a safer place and re-built the village. What I was witnessing was the last step in moving the remaining roofing slates to the new village. I carried on walking up the track contemplating the stoic, hard-working approach of the villagers and the challenges of living in this remote mountain landscape. A few hundred yards up the track we came to the edge of the landslide.  A new track had already been trampled, snaking its way precariously through the morass of sand, mud and rock and showing us our route on up the valley. A tongue of loose material thousands of feet long had spewed down the side of the mountain, with rock shards of all sizes, smothering all before it including the previous location of the village.

The mountain landscape that I had been walking through on this trek around Manaslu, up to the high pass at Larkye La at 5106m was epic in many ways. As a geologist it constantly contrasted the seemingly static geology of the UK with a landscape that was active in all too human timescales and on a scale that was sometimes hard to comprehend. Just recently in Uttarakhand, a part of the Indian Himalayas, a probable glacial collapse on the Nanda Devi glacier caused a flood which ripped down the Rishiganga River wiping out a hydro-electric dam and killing some 150 people. In 2015 an earthquake centered at Gorkha, close to my starting point for the Manaslu trek, killed some 9,000 people with another 22,000 sustaining injuries and over 600,000 homes destroyed. There was frequent evidence on my trek for recent landslides as the still rising Himalayas are cut deep by boulder-choked rivers, cracked by ice and shaken by earthquakes. There was no question that this was a landscape which was actively being formed.

It is not all destruction though. The massive scale of erosion in the mountains creates massive amounts of sedimentary material. Within the Budhi Gandaki River, which provided my route in around the east of Manaslu, there were places where piles of sediment many hundreds of meters thick had accumulated. These in turn had been cut into by the river exposing the extent of these recent accumulations in crumbling cliff-faces by the river. Further down-stream where the valley spreads out from the mountain front, enormous volumes of coarse sand and gravel accumulates providing aggregate for concrete, made visible in the form of piles of locally made concrete bricks drying in the sun.

Further east in Nepal lies Kathmandu and the Bagmati River. This river is holy to both Buddhists and Hindus and winds its way around the east and south of Nepal’s capital city. The Bagmati river basin is sandwiched between the massive Gandaki basin to the west and the equally large Kosi basin to the east. Unlike its neighbours which count the highest Himalayan peaks within their patch (Everest is part of the Kosi basin and Annapurna is within the Gandaki basin) the Bagmati river is rain fed rather than gorged on glacial meltwater. In the Kathmandu valley it is a slow river running across the top of the pile of sand and clay that marks where a large lake has silted up, filling in and levelling the valley. This ancient lake not only gave the valley its fertility but provides the area with another valuable resource, clay. The town of Thime to the east of Kathmandu is the pottery making centre of the district, though clay work can be seen throughout the Kathmandu Valley. Just to the north of Bhaktapur (the city of temples 8 miles east of Kathmandu) there are brick making chimneys surrounded by vast piles of bricks, like a Nepalese version of Bedfordshire. The clay isn’t just used for pots, bricks and tiles. Part of the extraordinary architecture of Bhaktapur and the other towns of the Kathmandu valley includes intricate relief patterns made from moulds to create patterned bricks in terracotta-red. These are combined with wood and stone to produce beautiful relief panels, architraves and other features. This work which reached its apogee between 1500 and 1800 AD is part of the reason that the Kathmandu Valley was listed as a World Heritage Site. The citation includes this statement “These monuments were defined by the outstanding cultural traditions of the Newars, manifested in their unique urban settlements, buildings and structures with intricate ornamentation displaying outstanding craftsmanship in brick, stone, timber and bronze that are some of the most highly developed in the world”.

The sedimentary picture painted in the Himalayas has huge brush strokes illustrating in bold the different types of sedimentary process. It shows the power in the forces of wind, water, ice and earth movement to erode. It demonstrates in extremes the relationship between energy and sediment grain-size from the house sized boulders moved by the raging meltwater in mountain rivers to the finest particles of clay filling the still waters of ancient Lake Kathmandu. It also gives a vivid rendering of the karmic nature of sedimentary environments, the give and take that erodes and deposits, creating both destruction and valuable resources.

In a place of extremes like the Himalayas this is all made obvious, though these principles apply just as much in other environments. If we travel the many thousands of miles in distance back to the landscape around Hadrian’s Wall and back in time for 300 million years or so to the Carboniferous period, the same things were happening. The layered stratigraphy of the rocks, varying from sandstone through siltstone to shale and coal speak of the different energies of the environments in which they were laid down. The estimated 2km thickness of Carboniferous sediments preserved in the Northumberland basin points to the huge volume of sediments eroded from the Himalayan scale mountains to the north, the eroded roots of which can now be seen in the Highlands of Scotland. In the same way that the Newars of Kathmandu benefited from the lacustrine resources of the Valley, we too have benefitted from the stone, coal, clay, iron and limestone found in the Carboniferous sedimentary sequences.

The give and take of the Carboniferous sediments is more subtly drawn in the mystery rock in this month’s WallCAP newsletter. Imagine a river going into the dry season, such that the river dwindles into still discontinuous pools in which the remaining sand and clay settle out. The pools then dry out producing a crust of partially hardened silt. Sometime later the weather breaks, a massive storm lashes down soaking the landscape and creating flash floods which create fast flowing turbid rivers. When these rivers overwhelm the old dried out pools, the power of the flow rips up the partially hardened muddy sand breaking it into fragments and carrying them along in the flood. Further down-stream as the current wanes these muddy clasts are redeposited mixed in with sand carried easily in the fast-flowing water. This is this sort of deposit that we are observing in this month’s mystery rock. It is what geologists call a lag deposit and a nice example of the way that sedimentary rocks don’t just record a sequence of deposition but also one of erosion and redeposition too.

https://www.youtube.com/watch?v=I0o1AhGuwMg&feature=youtu.be

@Northumbrianman

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