Gold in the Emerald Isle

Our speaker for 12 March 2008 was Dr Norman Moles of the University of Brighton. Before outlining the topics to be covered, he apologised for the not surprising fact that he had no samples to display! The topics were:-

1) Prehistoric and historical evidence for sources for gold.

2) Gold mineralization in north west Ireland.

3) Microchemical characterisation of alluvial gold.

4) A source of Bronze Age gold in the Mourne mountains.

5) The origin of alluvial gold in the Gold Mines River, Co.Wicklow.

Irish gold artefacts from the Bronze and Iron Ages are unique in Europe. 1100 pieces have been found, the majority being from the Bronze Age. The provenance of about a third is known to be a particular area. The actual years covered are therefore 2,500BC (early Bronze Age) to 500 BC (Iron Age). The examples illustrated showed the increasing skill and sophistication of the workmanship. It had been thought that much of the gold had been imported, but now it is known that it is more likely to be Irish gold from many sources. Although there is no evidence of mining at these sites, there are recorded references to early discoveries of gold in Ireland. One such reference being The Annals of the Four Masters - 1632, which refers to the discovery of gold in 1600 BC approx. and also mentions that gold was smelted in the forests south of Dublin. One source here was a gold-rich vein from Tipperkevin to Wicklow. Other historical references include the panning of gold from the Moyola River in Northern Ireland - 1652 and Avoca to Wicklow in 1753. The finding of gold in what was later called Gold Mines River, started a local gold rush in 1795. At this latter location, Ballinagore to Red Hole, was a particularly rich source. Panning here by local people lasted some six weeks before the government took over.

In the north of Ireland the presence of gold was reported before 1980 in many localities, but systematic searches did not commence until that date. An important site in the north was at Curraghinalt and Cavanacaw near Omagh. The gold here occurs in the Dalradian (Pre-Cambrian) sediments and is associated with Arsenopyrite-Stibnite veins of the Lower Paleozoic. Dr Mole then showed us a number of maps which revealed the mineralization of north west Ireland. A map was produced in 1976 by John Arthurs and in 2002 the mapping of north west Ireland was completed. It was then realised that the presence of arsenic in stream sediments coincided with the gold that is now mined in the Curraghinalt and Cavanacaw region. In 1981 exploration licences were obtained as part of the Ennex Exploration program.

In 1999 Nickelodeon acquired a licence for 0.5 million dollars and in 2003 Turnagain Resources implemented further exploration with a view to opening a mine. Curraghinalt is located in the Omagh Thrust alignment with east west faults of the Carboniferous half-graben. Together with Cavanacaw, which is five miles WSW of Omagh, serious mining began in 2000 with the production of Certified Irish Gold and the making of high-end jewellery by the company Galantas.

Dr Mole then demonstrated some of the investigations he and his colleague, Rob Chapman, of the University of Leeds have carried out. Careful study of the characteristics of gold grains may show the source of gold artefacts. Physical size and microchemical analyses were both important. Alloy composition and inclusion assemblages (transparent and opaque) were used to describe populations of gold. Samples collected were mounted up and examined with an electron microscope. Levels of copper, silver and other elements were measured. A map of the British Isles was shown which indicated in particular where high levels of silver are present.

One important source of gold in Ireland is the Mourne Mountains, north of Dublin. Richard Warner and Rob Chapman have produced a study of gold and other artefacts to prove their provenance. Some contain copper, which is red in colour but deliberate alloying was not likely. In the region, Hilltown and Ballincurry produced good samples, indicating levels of copper and silver. Irish gold has less copper than the artefacts and so Dr Mole will return in April for more exploration to find any copper-rich gold.

The final aspect demonstrated was the origin of gold in the Gold Mines River area. The source of gold in this region is in the periglacial and glacial till in the river valleys. Particular places mentioned were: Avoca, Woodenbridge and the Croghan Kinshelagh Mountains, which are the source of the local rivers. The deposits found were divided into types according to their mineral content. For example, Red Hole, being type 3, grains contain 8-14% silver. Also present could be sulphide and antimony.

The geological make-up of the Avoca area is Felsic volcanics with the intrusion of dolerite. Bedrock source in the valley is close to the alluvial cut-off point dating from the Late Tertiary or inter-glacial. The sediments are preserved in the deep valleys formed by glaciers. The general conclusion to date is therefore that the gold in the artefacts was obtained locally and not transported. Dr Mole then answered questions from members before Frank expressed heartfelt thanks for a most intriguing and interesting talk.

Valerie Bell

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Gordon's garden, again

Last year, as part of a long-overdue redesign of our garden, I dug some trenches to drain the lawn, and others to take the concrete footings of a low wall curving across its width. To my surprise, I found some interesting bits of ripple-marked Upper Tunbridge Wells Sand, and wondered what I might find if I dug up the rest of the lawn. But I sensed that my garden didn't share my enthusiasm.

I am Gordon’s garden, and although I had my say,

He’s taken not a scrap of notice, gone his own sweet way.

Not satisfied with dumping stuff he’s brought from far away,

He’s recently been eyeing me in quite a different way.

He’d noticed how my lawn becomes so boggy when there’s rain,

And dug a string of trenches filled with gravel so they drain.

(It’s ruined my appearance. Oh, he really is a pain!)

But what he found took me aback –– perhaps I’d best explain.

 

For as he dug, he came across a sandstone block or two.

I saw him get his hand-lens out to get a closer view.

He looked at them . . . he looked at me . . . and all at once I knew

He wouldn’t stop at drainage trenches. Help! What could I do?

And, sure enough, he came with spade and shovel in his hand,

And devastated even more of my once-virgin land.

He claimed it was for footings, that the whole thing was pre-planned.

Pre-planned, my foot! Such willful desecration should be banned.

He says I’ll look much nicer when he’s dug a little more.

He says his stone is ripple-marked and shows how, long before,

My ancestors had lazed around upon some wave-kissed shore.

Oh no! I bet he’ll dig until he finds a dinosaur

Well, I am Gordon’s garden, and it’s time for me to say

That up with this I will not put. That’s it. No more, okay?

I have a secret weapon: when it’s wet, it’s sticky grey;

But when his drains dry out my soil, it’s hard, rock-solid clay !

Gordon Judge

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More on the Deccan Traps

The ‘huge volumes of gases’ referred to in my article on pages 17-18 of the March issue of Stonechat have now been quantified by a group from the Open University, according to an article in the magazine Science. They conclude that the eruptions which formed the Traps released an annual flux of at least 300 - 500 million tonnes of sulphur dioxide, which would have persisted high in the ancient atmosphere for decades and been likely to have had serious effects upon Late Cretaceous environments and climate. (Worryingly, this is ‘only’ two or three times the 150 million tonnes or so said to be emitted by today’s industrial processes.)

The group examined hundreds of rock samples from the Traps and cut thin slices from them. In just a few of these slices, they found find tiny pockets of glass. They were able to measure the sulphur and chlorine ‘frozen’ in the glass, and so determine the lava’s original gas content.

‘This research,’ said the OU’s Dr. Mike Widdowson, ‘can provide vital data that we can now hand over to climate modellers as they search for ways to explain how pollution will hurt the atmosphere.’

Gordon Judge

[Main source: www3.open.ac.uk/media/fullstory.aspx?id=13340]

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Building Stones of Sussex

The April Evening Talk was given by Roger Cordiner. Following a varied career, he is now a lecturer at the University of Brighton. It is here that he met, and has became a collaborator with, Roger Birch, their mutual interest being the Geology of Sussex. It is in this capacity that he came to speak to us on the local building stones. He and Roger have been concentrating on West Sussex, making numerous weekend forays to churches and other ancient local buildings in order to examine the various stones used in their construction.

Roger pointed out that there were relatively few exposures of rock in Sussex, and thus the local buildings afford an excellent opportunity for the examination of the underlying rocks of the county. Prior to the advent of the railways and the easy transportation of heavy materials (circa 1850), much of the stone used in the construction of a building was quite local to a given area. Thus buildings serve as accessible 'exposures', although of course there can be no recourse to a good hammering! Even the use of HCl has to be a rather surreptitious operation! Furthermore, many of the quarries which were open in the past have now been filled and consequently have disappeared.

He went on to describe the geology of West Sussex: the map showing the familiar 'horseshoe' at the west of the Weald, and the associated vertical geological column. Roger then looked in detail at the geological divisions and described the rocks associated with them. For instance, from the Quaternary, Iron Pan is obtained. From the Holocene comes Travertine, whilst the Neogene holds Sarsens. In the Paleogene, there is Bognor Rock. From the Upper Cretaceous comes the Flint and Hythe Stone, and finally from the Lower Cretaceous, Horsham Stone and Ardingly Sandstone have been quarried.

He then described some of the buildings that he and Roger have visited, taking them in order of the era in which they were built, from Roman times through to the Medieval. He described various architectural styles, from the robust Saxon by way of the solid Norman to the beautiful English Perpendicular. He illustrated his talk with images of the local buildings associated with these styles and, of course, the stones listed above that were used in their construction. He gave an excellent account of our two local stones from the north of the county, the Horsham Stone and the Sussex Marble. The whole was illustrated by some superb photographs. Roger gave us a most interesting lecture, and it was particularly compelling because of the relevance of his material to our own area. Not only were the building stones familiar, but also many of the buildings themselves were well known to us. Clearly he and Roger have put in a great deal of enthusiastic research, not to mention the distance which they must have covered in the process. I was quite relieved to hear the admission from these two professional geologists that even they could not identify all the stones which they encountered, an experience all too familiar to myself! Thanks again to Roger for making the journey from Bognor to give us an excellent talk.

Peter Webster

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An Amazing Water Source.

 

This was seen on a label of bottled water on a recent visit to Spain:

'VICHY CATALAN starts life at the Earth's centre. It ascends slowly before finally emerging at 60degC. Along the way it generates its characteristic personality and is enriched with minerals that help you feel better.’

I wonder how it percolates through that lump of nickel-iron thereabouts.

Peter Webster

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The Urals

 

The Urals were named after the Uralian tribe that was once native to the northern region of Asia. They were hunter/gatherers, but lack of plentiful resources in the area forced them to relocate, spreading throughout the Asian region.

The range is aligned north/south and lies mostly just to the west of longitude 60E E, forming a natural boundary between Europe and Asia. It stretches for 1500 miles northwards from the Kirgiz Steppe to the islands of Vaygach and Novaya Zemlya in the Arctic Ocean. It is rich in minerals, including gold, platinum, coal iron, nickel and silver, and the semi-precious topaz and beryl.

Much of the range is heavily forested. In the south the tree line reaches 1400m (4600 ft.), dropping to sea level in the north. The virgin Komi Forests towards the north are recognised as a World Heritage site.

Towns and settlements are mostly small, often based on mining, but where the Trans-Siberian Railway crosses the range stands the fifth largest town in Russia, Yekaterinburg, whose latitude is about 57E N (that of Fort William). Between 1924 and 1991 the town was known as Sverdlovsk, named after a communist hero of the Russian Revolution. It now has a population of 1,300,000 and is a leading industrial and cultural centre, having numerous institutes of higher education covering forestry, mining, agriculture, law, medicine, teacher-training and scientific research. It was here that Tsar Nicholas II and his family were murdered.

Near the mountains in the south, in the province of Chelyabinsk, is the Soviet nuclear facility called the Mayak Chemical Combine. From 1948 until 1990, when the last of five reactors was shut down, the Combine contaminated the region to such an extent that it is now known as the most polluted area on Earth. The region received this title due to the Combine’s disregard for environmental and public safety; more specifically there are three incidents that stand out - intentional dumping of radioactive waste into the Techa River, an explosion at a radioactive waste storage facility in 1957, and a 1967 wind storm that deposited irradiated sediments from Lake Karachay on to the surrounding province.

Sir Roderick Murchison was commissioned by the Tsar of Russia to assess the mineral wealth of the country and as part of his journey of 14,000 miles in the summer of 1841, Murchison drew a number of cross-sections of the Urals. He took the opportunity to observe the strata from river cuttings. An extract from my book, King of Siluria, tells part of the story: Murchison’s journal had the following entry: ‘The descent of the Serebrianska [about 58E N] was one of the most memorable days of my life. The distance to be accomplished by this winding stream was seventy versts, or nearly fifty English miles. When I went to rest, the bed of the river was almost quite dry, with not water enough to drown a rat, and yet we were to effect the miracle of floating down in a six-oared boat. When I awoke a furious stream was rushing down, and the natives were beginning to get canoes. The good commandant [M. Moskvin], having the Imperial order that I was to descend by water, had let off an upper lake [the Zavod], and thus made a river in a fine dry sunny day!

‘The waters having been let off for us, and the river bed filled, we effected our embarkation amid three cheers. The river was muddy, and had rocks hidden, with very sharp curves of the stream. With a hundred groundings and stoppages, we got tired of our big boat of honour, and took to the canoes. These answered well for a while, but trusting to shoot through some stakes and nets (myself on my back at the head of the canoe), we (i.e. de Verneuil and myself) were capsized in a strong current. I saved my notebook (see the stains), but my cloak, bag, pipe, etc., went floating down. A curious scene followed, after we had scrambled out to the shore. The other canoe shot by and picked up our floating apparatus. Fortunately this letting off the waters had brought down some natives to catch fish, and they had a fire, by which we dried ourselves, whilst their large wolf-dogs lay around us. When we re-embarked, we shot several ducks (Merjanier), and here and there found limestones and shales striking to the N.N.W. Some of the limestones were charged with Devonian fossils.

‘After this, evening began to fall. Saddles, anticlinals and synclinals arose in magnificent masses on the rocky banks, but our boat-bottom was soon knocked to pieces by grounding at least a hundred times, and whisking round as in a waltz at each shock. It now filled so rapidly that we had just time to escape. We had then a fine evening scene. We landed on shingle, and got into the forest, not having seen a house or hut for fifty miles. The dense wildness of the scene, the jungle and intricacy of a Russian forest, can never be forgotten. We had to cross fallen trees and branches, and to force through underwood up to our necks.

‘After our various night evolutions, sometimes by land and sometimes by water, we finally reached our “derevna” (Ust Serebrianska) at two a.m., wet up to the middle, by walking through moist jungle and meadow. Our men were very amphibia, and required no food. They had been half the day in that stream, pulling, hauling, shoving, and shouting, and never eating or drinking. We had to awake the chief peasant’s family, and were soon in a fine hot room, with children sleeping all about.’

                                                                                  John Morton

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Dinosaur dam

(A short note in New Scientist, followed by a bit of Googling, has produced this.)

In the Heilongjiang Province of north-east China is Dinosaur Mountain. According to a recent report (22 October 2007) in the China Daily, Dinosaur Mountain ‘sits right on the river that forms the boundary between China and Russia’ - the Heilongjiang River. The mountain used to be called Mountain of Dinosaur Bones because thousands of dinosaur bones have been unearthed from it in the past. Some thirteen skeletons have been assembled from these remains and are now exhibited in several museums throughout China.

But Dinosaur Mountain is believed still to hold enough fossil bones to put together another hundred or more dinosaur skeletons. Every summer, rising waters and strong currents erode parts of the mountain, leaving dinosaur fossils exposed. ‘Many fossils have been washed away in the past,’ said Li Jinshan, Vice Director of Jiayin Dinosaur National Geologic Park Administrative Bureau. (An opportunity for geologists downstream?)

So three years ago the Land and Resources Department of Heilongjiang Province ordered that a 1450 m earth dam, 5.5 metres high and 10 metres wide, be built on the Chinese bank of the river, to stop the fossils from being washed away. For three years workers have contended with rising waters and strong currents in summer and long cold winters at high altitude, but the job is now completed, says the report.

                                                                                    Gordon Judge

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 Geological Anniversaries and `Local Heroes'

 

 

Dr Frederick Dixon (1799-1849) was the youngest of three sons of Rector of Sullington, a downland parish. He qualified as doctor at St Bartholomew's Hospital, married, honeymooned round the Mediterranean and then came to live in Worthing in 1827. He had a lifelong fervent interest in fossils of the Chalk and Early Tertiaries of West Sussex. He was a friend of Gideon Mantell, Peter John Martin, etc, and, in particular, of Richard Owen. He was elected FGS (1840) supported by Mantell, Lyell and Murchison and died suddenly in September 1849, leaving his magnificent opus on Geology of Sussex unfinished. This was brought to publication by Richard Owen in Dec 1850 and contains 44 superb plates of fossils: it is still a standard work of reference. He spent 20 years amassing a significant fossil collection (4500 specimens), which his widow sold to the BM. The collection was dispersed but its catalogue survives. His work is second only to that of Mantell in its geological significance in Sussex. Dr Dixon was well-known in geological circles in the 1830s/40s, decades of great significance in the history of geology, and was influential in many of the important debates in those times. The West Sussex Geological Society will celebrate Dixon in three events:1) A two-week Exhibition in the foyer of Worthing Library about the Life, Times and Work of Dr Dixon either side of:

2) A Public Evening Lecture in Worthing Library Lecture Theatre on Friday 4 April on Frederick Dixon and the Geology of Sussex, by Anthony Brook

3) A Field Trip on Saturday 5 April to The Trundle and Bracklesham Bay, led by David Bone (who has been researching this area for 35 years) on a day with a mid-afternoon low tide, to view Dixon's field area, collect similar fossils and evaluate his pioneering contributions, alongside work by 20th-century researchers such as Martin Venables and the Tertiary Research Group.

For further details contact: Tony Brook e-mail: Anthony.brook27@btinternet.com

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 Libya’s Great Man-made River

It’s a geological fact, a geographical mis-match and an expensive logistical challenge: Libya has large reserves of fresh water beneath its Saharan deserts, far away from the large urban populations along its coastline. But in October 1983, the Great Man-made River Authority was created to respond to the challenge.Work started in Sarir in 1984. Pipeline water had reached Benghazi from the eastern desert by 1993, and Tripoli, from the western well-fields, by September 1996. In March 2006, Phase III, which links the two earlier Phases, was ‘still under construction’. In September 2007, the water had reached Gharyan, 50 km south of Tripoli. The final two Phases involve the extension of the distribution network together with the construction of a pipeline linking the Ajdabiya reservoir to Tobruk, and finally the connection at Sirt of the eastern and western systems into a single network.Articles on the internet about the project are full of big numbers (not always mutually consistent): total costs are in the region of $30 billion; two special factories, built to manufacture the pre-stressed concrete pipe sections, used some 2500 tonnes of cement per day; each pipe section is 4 m in diameter, 7.5 m long and weighs up to 86 tonnes; there are 1300 wells, and about 5000 km of pipeline laid in trenches about 7 m deep. When complete, the plan is that some 155,000 hectares of land will be irrigated by up to 6.5 million cubic metres of fresh water a day to produce 270,000 tons of crops, three times as much fodder and an ‘abundance’ of fruit and vegetables. The Lonely Planet’s 2002 guide to Libya notes that the project aimed to set up 37,000 model farms and increase wheat production in the north by 180,000 hectares. The water lies deep underground in four major basins. In total, they are said to hold over 35,000 cubic kilometres of ‘fossil’ water.The sedimentary basins from which the water is to be drawn were formed during the tectonic plate movements at the end of the Mesozoic which created the Red Sea and Morocco’s Atlas Mountains. The water now trapped in this porous Nubian Sandstone has been there since North Africa had a temperate climate between 40,000 and 10,000 years ago.Although tectonic activity has quietened, there are still rumbles of the geo-political sort. Bizarrely, in 1997 the CIA was apparently convinced that the pipelines were hiding a vast infrastructure of secret military tunnels and underground weapons storage facilities. Perhaps more significantly, some hydrologists believe that the rapid depletion of the aquifers could lead to seepage from the Nile; and if the Nile is threatened, says an Egyptian journalist, Egyptian intelligence services are ‘not averse to invading’. Geologists, meanwhile, fear that seepage, combined with freezing desert temperatures, could cause trapped frozen water to crack sub-strata, and damage the desert. Lonely Planet quotes ‘evidence to suggest that the GMMR has begun to lower the ground-water table in north-western Libya, with potentially disastrous consequences for agriculture’. Tuareg tribes have reported drier wells, though there’s no proven link to the GMMR. And in 2002, a project manager reported that some pipes were so corroded that the River was shut down at least three times.

Libyan leader Colonel Muammar al-Qaddafi has described it as the ‘eighth wonder of the world’. For now, perhaps. But this is a project with a limited life. The basins are not expected to refill. If you divide their huge volume by the daily flow rate given above, you get a lifespan of 14,752 years. But that must be too simple a calculation: sceptical experts reckon the water will flow for only between 15 and 50 years. Perhaps coincidentally, 50 years is also the reported design life of the concrete pipe sections.

Gordon Judge

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Lisbon, 1755

The Reverend Charles Davy knew what an earthquake felt like. He had endured a fairly mild one in Madeira some six or seven years ago. Today, November 1st, 1755, as he sat writing after breakfast, he was reminded of his earlier experience. In his first-floor apartment among the narrow streets of Lisbon, his writing table trembled gently and his papers moved as if blown by the wind. But there was no wind: the sun shone brightly in a cloudless sky.

Then the house itself shook. The Reverend quickly rejected any idea that passing coaches must be rumbling past in the street below, in favour of his Madeiran memory. The hollow thundering, ‘a strange frightful kind of noise underground’, lasted less than a minute but was enough to convince him that it was the sound of an imminent earthquake. Abandoning his pen, he hesitated, wondering whether, like Madeira, it might not be too bad –– would it be it safer to stay in the house or risk injury in the streets? But a mighty crash, ‘’as if every edifice in the city had tumbled down at once’, soon resolved his quandary.

The house shook, and its upper stories collapsed. In his first-floor room, the walls rocked and fell away in several places; large stones and roof timbers fell all about him; and the sky took on ‘an Egyptian darkness’. Choking with the dust, Charles hurried out of the remains of his house and through the streets towards the River Tagus. He dodged collapsing buildings and clambered over the ruins of St. Paul’s Church to arrive at the riverside among ‘a prodigious concourse of people of both sexes and all ranks and conditions’. He noted priests, purple-robed church dignitaries, and ‘ladies half dressed and some without shoes’ among the crowds who were now on their knees, praying for mercy.

A second shock then completed the destruction of the remaining buildings, including a parish church on St. Catherine’s Hill, to where another crowd had fled. Many were killed on the spot, others mortally wounded. Though less violent than the first, this second shock nearly toppled Rev. Davy from his knees. Then came the cry: ‘The sea is coming in, we shall all be lost!’ The river, some four miles broad at that point, was ‘heaving and swelling in the most unaccountable manner’, and on this swell appeared a huge wave, ‘rising as it were like a mountain . . . foaming and roaring’. The whole company ran for their lives: many were swept away; others who had reached higher ground were up to their chests in water; and our hero survived by clinging to a large beam until the surge had passed.

Clearly, the Davy brain reckoned, the idea that the river bank was safer than the city was now questionable, so with dripping clothes, he retreated to where St. Paul’s had been. Here, he watched ships being tossed about on the violent waters below ‘as if in a violent storm’, yet without any wind; and he witnessed ‘the fine new quay, built of marble, at an immense expense . . . entirely swallowed up, with all the people on it who had fled thither for safety’.

In his account, the Reverend Davy records another incident reported to him by a friend on the opposite side of the Tagus. No sooner had the river surge passed his friend’s house, than ‘immediately a great number of small fissures appeared in several contiguous pieces of ground, from whence they spouted out, like a jet stream, a large quantity of fine white sand to a prodigious height’. People around him had reported sulphurous smells, though he had not noticed this himself.

Then came the third shock. Again the sea rushed in, reaching, even at his now more elevated position, up to his knees. The surge retreated rapidly, but then repeated its actions several times in succession. Davy notes that the devastation would have been greater if ‘the force of the waves had not been somewhat broken by the winding of the bay’.

So even on this higher ground he was not safe. Where could he go now? Of course –– why hadn’t he thought of it before? What building in the city is built low and very, very strong? Why, the Mint, of course! When he arrived at its entrance he found it guarded only by the eighteen-year-old commanding officer of the guard, remaining loyally at his post after all his soldiers had fled. Davy was most impressed with the young man’s courage and steadfastness, and told him so; but with the tremors continuing, and the houses opposite the Mint tottering alarmingly, the two men ‘retired inward to a hillock of stones and rubbish’.

When darkness came, fires which had broken out in the city were so bright that one could see to read. They continued unabated for six days. Davy suspected they had been started, not by the earthquake, but by the combination three causes: burning lamps and wax tapers that decorated every church for All Saints’ Day setting fire to curtains and timber when the buildings fell; the houses’ own kitchen fires; and arson by ‘hardened villains’ released by the destruction of their prison.

Ever interested in detail, the Reverend Davy noted that ‘with regard to the buildings, it was observed that the solidest  in general fell the first’. He reckoned that ‘the whole number of persons that perished, including those who were burned or afterwards crushed to death whilst digging in the ruins, is supposed, on the lowest calculation, to amount to more than sixty thousand’.

Gordon Judge

[Based on a modernised version of Rev. Davy’s account given in the Internet Modern History Sourcebook, on-line at www.fordham.edu/halsall/mod/1755lisbonquake.html.]

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Postscript: Lisbon and Atlantis

A paper in the European Review by M.-A. Gutscher, of the Institut Universitaire Europeen de la Mer, last year suggests that the 1755 Lisbon earthquake was of magnitude 8.5––9. Although the fault that generated it has not been identified, recent data from the Gulf of Cadiz suggests an active east-dipping subduction zone beneath Gibraltar. Given that eleven out of the twelve strongest earthquakes in the past 100 years have happened along ‘subduction zone megathrusts’ –– including the December 2004 and March 2005 Sumatra earthquakes –– the author declares that ‘it appears likely that the 1755 earthquake and tsunami were generated in a similar fashion, along the shallow east-dipping subduction fault plane’.

Enthusiastically, the author goes on to interpret other records as possible evidence for ‘great earthquakes off south-west Iberia every 1500––2000 years’. What’s more, Roman records from Cadiz of just such an event around 200 BC are apparently ‘supported by tsunami deposits’. Now at academic fever pitch, the author notes that, according to Plato, it was ‘strong earthquakes and floods’ that destroyed Atlantis some 11,600 years ago.

With steam now erupting from an overheated brain, the author finally makes the crucial link. ‘A 1 m thick turbidite deposit, containing coarse-grained sediments from underwater avalanches, has been dated at 12,000 BP and may correspond to the destructive earthquake and tsunami described by Plato. The effects on a paleo-island (Spartel) in the Straits of Gibraltar would have been devastating, if inhabited, and may have formed the basis for the Atlantis legend.’

                                                                                Gordon Judge

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1755 Lisbon earthquake (from Wikipedia)

The 1755 Lisbon earthquake, also known as the Great Lisbon Earthquake, took place on November 1, 1755, at 9:40 in the morning. It was one of the most destructive and deadly earthquakes in history, killing between 60,000 and 100,000 people (though the exact number is uncertain). The earthquake was followed by a tsunami and fire, resulting in the near-total destruction of Lisbon. The earthquake accentuated political tensions in Portugal and profoundly disrupted the country's eighteenth-century colonial ambitions.

The event was widely discussed by European Enlightenment philosophers, and inspired major developments in theodicy and in the philosophy of the sublime. As the first earthquake studied scientifically for its effects over a large area, it signalled the birth of modern seismology. Geologists today estimate the Lisbon earthquake approached magnitude 9 on the Richter scale, with an epicentre in the Atlantic Ocean about 200 km (120 mi) west-southwest of Cape St. Vincent.

 

The earthquake

The earthquake struck on the morning of 1 November, the Catholic holiday of All Saints' Day. Contemporary reports state that the earthquake lasted between three-and-a-half and six minutes, causing gigantic fissures five metres (16 ft) wide to appear in the city centre. The survivors rushed to the open space of the docks for safety and watched as the water receded, revealing a sea floor littered by lost cargo and old shipwrecks. Approximately forty minutes after the earthquake, an enormous tsunami engulfed the harbour and downtown, rushing up the Tagus river. It was followed by two more waves. In the areas unaffected by the tsunami, fire quickly broke out, and flames raged for five days.

Lisbon was not the only Portuguese city affected by the catastrophe. Throughout the south of the country, in particular the Algarve, destruction was rampant. The shockwaves of the earthquake were felt throughout Europe as far as Finland and North Africa. Tsunamis up to 20 metres (66 ft) in height swept the coast of North Africa, and struck Martinique and Barbados across the Atlantic. A three-metre (ten-foot) tsunami hit the southern English coast. Galway, on the west coast of Ireland, was also hit, resulting in the partial destruction of the ‘Spanish Arch’.

Of a Lisbon population of 275,000, up to 90,000 were killed. Another 10,000 were killed in Morocco.  Eighty-five percent of Lisbon's buildings were destroyed, including famous palaces and libraries, as well as most examples of Portugal's distinctive 16th-century Manueline architecture. Several buildings that had suffered little earthquake damage were destroyed by the subsequent fire. The brand new Opera House, opened only six months before (under the ill-fated name Phoenix Opera), was burned to the ground. The Royal Ribeira Palace, which stood just beside the Tagus river in the modern square of Terreiro do Paço, was destroyed by the earthquake and tsunami. Inside, the 70,000-volume royal library as well as hundreds of works of art, including paintings by Titian, Rubens, and Correggio, were lost. The royal archives disappeared together with detailed historical records of explorations by Vasco da Gama and other early navigators. The earthquake also damaged major churches in Lisbon, namely the Lisbon Cathedral, the Basilicas of São Paulo, Santa Catarina, São Vicente de Fora, and the Misericordia Church. The Royal Hospital of All Saints (the biggest public hospital at the time) in the Rossio square was consumed by fire and hundreds of patients burned to death. The tomb of national hero Nuno Álvares Pereira was also lost. Visitors to Lisbon may still walk the ruins of the Carmo Convent, which were preserved to remind Lisboners of the destruction.

It is said that many animals sensed danger and fled to higher ground before the water arrived. The Lisbon quake is the first documented reporting of such a phenomenon in Europe.

 

The day after

Owing to a stroke of luck, the royal family escaped unharmed from the catastrophe. King Joseph I of Portugal and the court had left the city, after attending mass at sunrise, fulfilling the wish of one of the king's daughters to spend the holiday away from Lisbon. After the catastrophe, Joseph I developed a fear of living within walls, and the court was accommodated in a huge complex of tents and pavilions in the hills of Ajuda, then on the outskirts of Lisbon. The king's claustrophobia never waned, and it was only after Joseph's death that his daughter Maria I of Portugal began building the royal Ajuda Palace, which still stands on the site of the old tented camp. Like the King, the Prime Minister Sebastião de Melo (the Marquis of Pombal) survived the earthquake. ‘Now? Bury the dead and take care of the living,’ he is reported to have said, and with the pragmatism that characterized his coming rule, the Prime Minister immediately began organizing the recovery and reconstruction. He sent firefighters into the city to extinguish the flames, and ordered teams to remove the thousands of corpses before disease spread. Contrary to custom and against the wishes of representatives of the Church, many corpses were loaded on to barges and buried at sea beyond the mouth of the Tagus. To prevent disorder in the ruined city, and, in particular, as a deterrent against looting, gallows were constructed at high points around the city and at least thirty-four people were executed. The Portuguese Army surrounded the city to prevent the able-bodied from fleeing, so that they could be pressed into clearing the ruins.

Not long after the initial crisis, the Prime Minister and the King quickly hired architects and engineers, and less than a year later, Lisbon was free from debris and undergoing reconstruction. The King was keen to have a new, perfectly-ordained city. Big squares and rectilinear, large avenues were the mottos of the new Lisbon. At the time, somebody asked the Marquis of Pombal about the need for such wide streets. The marquis answered: ‘one day they will be small.’ Indeed, the chaotic traffic of Lisbon today reflects the wisdom of his reply.

Pombaline buildings are among the first seismically-protected constructions in the World. Small wooden models were built for testing, and earthquakes were simulated by marching troops around them. Lisbon's ‘new’ downtown, known today as the Pombaline Downtown (Baixa Pombalina), is one of the city's famed attractions. Sections of other Portuguese cities, like the Vila Real de Santo António in Algarve, were also rebuilt along Pombaline principles.

The earthquake shook much more than cities and buildings. Lisbon was the capital of a devout Catholic country, with a history of investments in the church and evangelism in the colonies. Moreover, the catastrophe struck on a Catholic holiday and destroyed almost every important church. For eighteenth-century theology and philosophy, this manifestation of the anger of God was difficult to explain.

The earthquake strongly influenced many thinkers of the European Enlightenment. Many contemporary philosophers mentioned or alluded to the earthquake in their writings, notably Voltaire in Candide and in his Poème sur le désastre de Lisbonne (‘Poem on the Lisbon disaster’). Voltaire's Candide attacks the notion that all is for the best in this, ‘the best of all possible worlds’, a world closely supervised by a benevolent deity. The Lisbon disaster provided a salutary counterexample. As Theodor Adorno wrote, ‘[t]he earthquake of Lisbon sufficed to cure Voltaire of the theodicy of Leibniz’. In the later twentieth century, following Adorno, the 1755 earthquake has sometimes been compared to the Holocaust as a catastrophe so tremendous as to have a transformative impact on European culture and philosophy.

Jean-Jacques Rousseau was also influenced by the devastation following the earthquake, whose severity he believed was due to too many people living within the close quarters of the city. Rousseau used the earthquake as an argument against cities as part of his desire for a more naturalistic way of life.

The concept of the sublime, though it existed before 1755, was developed in philosophy and elevated to greater importance by Immanuel Kant, in part as a result of his attempts to comprehend the enormity of the Lisbon quake and tsunami. Kant published three separate texts on the Lisbon earthquake. The young Kant, fascinated with the earthquake, collected all the information available to him in news pamphlets, and used it to formulate a theory of the causes of earthquakes. Kant's theory, which involved the shifting of huge subterranean caverns filled with hot gases, was (though ultimately shown to be false) one of the first systematic modern attempts to explain earthquakes by positing natural, rather than supernatural, causes. According to Walter Benjamin, Kant's slim early book on the earthquake ‘probably represents the beginnings of scientific geography in Germany. And certainly the beginnings of seismology.’

Werner Hamacher has claimed that the earthquake's consequences extended into the vocabulary of philosophy, making the common metaphor of firm ‘grounding’ for philosophers' arguments shaky and uncertain: ‘Under the impression exerted by the Lisbon earthquake, which touched the European mind in one [of] its more sensitive epochs, the metaphor of ground and tremor completely lost their apparent innocence; they were no longer merely figures of speech.’ Hamacher claims that the foundational certainty of Descartes' philosophy began to shake following the Lisbon earthquake.

In Portuguese internal politics, the earthquake was devastating. The Prime Minister was the favourite of the King, but the aristocracy despised him as an upstart son of a country squire. (Although the Prime Minister Sebastião de Melo is known today as Marquis of Pombal, the title was only granted in 1770, fifteen years after the earthquake.) The Prime Minister in turn disliked the old nobles, whom he considered corrupt and incapable of practical action. Before November 1, 1755 there was a constant struggle for power and royal favour, but afterwards, the competent response of the Marquis of Pombal effectively severed the power of the old aristocratic factions. Silent opposition and resentment of King Joseph I began to rise. This would culminate in an attempted assassination of the King, and the elimination of the powerful Duke of Aveiro and the Távora family.

 

The birth of seismology

The Prime Minister's response was not limited to the practicalities of reconstruction. The marquis ordered a query sent to all parishes of the country regarding the earthquake and its effects. Questions included: how long did the earthquake last? how many aftershocks were felt? what kind of damage was caused? did animals behave strangely? (this question anticipated studies by modern Chinese seismologists in the 1960s); what happened in wells and water holes?

The answers to these and other questions are still archived in the Tower of Tombo, the national historical archive. Studying and cross-referencing the priests' accounts, modern scientists were able to reconstruct the event from a scientific perspective. Without the query designed by the Marquis of Pombal, this would have been impossible. Because the marquis was the first to attempt an objective scientific description of the broad causes and consequences of an earthquake, he is regarded as a forerunner of modern seismological scientists.

The geological causes of this earthquake and the seismic activity in the region continue to be discussed and debated by contemporary scientists. Some geologists have suggested that the earthquake may indicate the early development of an Atlantic subduction zone, and the beginning of the closure of the Atlantic Ocean. Indeed, the only other recorded earthquakes of this size have been megathrust earthquakes involving subduction, making it all but certain that the Lisbon event was a megathrust earthquake as well.

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Meteorites, Myth, Mystery and Marvel

The lecture for November was given by Dr. Caroline Smith, Curator of Meteorites at the Natural History Museum. In the introduction to her talk, Caroline stressed the importance of the study of meteorites. These extra-terrestrial visitors bring with them a great deal of information. For instance, she described them as 'the windows on history' of the Universe. The number of meteorites available for study was rather limited until 1969, but since then expeditions to Antarctica have recovered some 24k specimens, raising the known total to some 33k: (and counting as the total is updated on the Web daily!). Collecting from an area of low humidity such as a desert is clearly advantageous, in that the rate of chemical decomposition is reduced, and there is no vegetation to obscure the specimen. Caroline then described the major types of meteorites.* These include iron meteorites, stony-iron meteorites and stony meteorites. She described some of the features of each, before describing her own particular enthusiasm for the stony meteorites, divided into Chondrites and Achondrites. Chondrites are some of the most primitive rocks in the solar system. These 4.5-billion-year-old meteorites have scarcely changed since leaving the parent asteroid. They have never really been hot enough to have melted. They have a very distinctive appearance made from droplets of silicate minerals, mixed together with small grains of sulphides and iron-nickel metal. This structure of millimetre-sized granules also gives chondrites their name, which comes from the Greek for sand grains 'chondres'. Achondrites include meteorites from asteroids, Mars and the moon. They are igneous, meaning that at some point they melted into magma. When the magma cools and crystallises, it creates a concentric layered structure. This process is known as igneous differentiation. The rocky planets of Mercury, Venus, Earth and Mars, have also been formed by igneous differentiation, giving them planetary crusts, mantles and cores. Achondrites can, therefore, tell us a lot about the internal structure and formation of the planets.

Caroline spoke with some warmth regarding a controversy of recent years: 'is there life on Mars?'. It has been suggested by some researchers that they have found traces of bacteria in some planetary achondrites. However, these discoveries have been discredited by the wider academic community as it would appear that these 'bacteria' can be identified as flaws in investigational techniques, such as 'dodgy' gold depositions in the electron microscopy work.

Having described the types of meteorites, Caroline then turned her attention to meteorites in the field. The first known modern case of a human hit by a space rock occurred on 30 November 1954 in Sylacauga, Alabama. There a 4 kg stone chondrite crashed through a roof and hit Ann Hodges in her living room after it bounced off her radio. She was badly bruised.

On May 5th 1991, a single stone fell in the garden of Mr. A. Pettifor, of Glatton, Cambridgeshire. Luckily, he was working in his garden at the time, otherwise the meteorite may not been found. Mr. Pettifor was startled by a loud whining noise and by the crash of the stone into a conifer hedge, some 20 metres from where he stood. He found a single crusted stone beneath the conifers. The stone had damaged part of a low hawthorn hedge 1.5 metres south of the conifers and had made a shallow depression about 2cm deep. It was warm, not hot, when first picked up. Mr. Pettifor was clearly exceedingly public-spirited and instead of selling his recent acquisition, he donated it to the N.H.M. **

We were then treated to the traditional show of 'holiday snaps'! Well, actually this was a lively and most entertaining account of her recent expedition to the Nullarbor Desert in Western Australia, which proved to be quite an adventure. The conditions were quite arduous, but there was an obvious compensation: meteorites. The dry conditions and the stony plane surface of the desert enabled the party of four to recover some nineteen specimens in four days. However, highly entertaining were her descriptions of the tribulations of being filmed by a BBC documentary crew. Even more entertaining was her graphic commentary, with the appropriate theatrical actions, when on waking in the early morning she found a spider sharing her swag.

The talk was followed by a lively questioning session, and as Frank commented, her talk had elicited more questions than any speaker in recent memory. It was indeed a thoroughly informative talk, both lively and entertaining, delivered with great enthusiasm and displaying clearly how engrossed Caroline is in her work. Yet again, the HGFC has been fortunate in receiving a guest speaker at the top of her field. Extra special thanks are due since Caroline was exceedingly busy at the time of writing, in that an exhibition of meteorites was to be opened in a few weeks at the N.H.M.

Peter Webster

1] Caroline's blog on her visit to the Nullarbor can easily be located. Enter 'Caroline Smith meteorites' into a search engine such as Google and her blog on the NHM site can be found. There are also photos there.

2] The Wikipedia entries for 'Meteorites' are interesting and useful.

3] * A detailed description of each type of meteorite can be found on the same NHM site as the Caroline's blog, referred to above.

4] **A couple of months after the event, the village had a summer fete. For a small admission charge people could view the 767gm meteorite, wrapped up in clingfilm, and to meet the finder Mr. Pettifor, the proceeds going to the local church fund. Item found on the Web, PJW

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An Antarctic Journey

The final lecture of the 2007 summer programme on July 11 was given by Mrs. Ann Fereday, in which she described her observations and experiences during a visit to South America, the Falklands and Antarctica.

She had a number of geological maps on show, and she began by talking about the Scotia Ridge, which showed clearly on her maps. The western extremity of this feature is to be found in the region of Patagonia. Here the dramatic granite towers, the Torres del Paine, climb into the sky. She described some of the features which she visited whilst waiting  in Ushuaia to board her ship.

On leaving the mainland of South America, via the Beagle Channel, her first landing was made on the Falklands Islands.   A succession of landings offered the opportunity to meet scores of penguins. The first of these species was the delightful Rockhopper Penguin. As to the geology, the collecting of hand specimens was not encouraged, given that there remained numerous land mines.

Her cruise then took her on to South Georgia, with its angular peaks rising sharply from the tumbling sea. She made landings on Albatross Island, encountering the peaceful Wandering Albatross. However, a landing can only be made after the potential visitor has run the gauntlet of the unfriendly and dangerous Fur Seals supervising the beaches. Whilst visiting Grytviken she encountered the decaying infrastructure of the once-flourishing whaling industry. A tiny graveyard on the outskirts of the hamlet is the resting place of that most famous explorer Ernest Shackleton, marked by an elegant, simple granite memorial.

Her ship then steamed southwards towards Antarctica, crossing the Scotia Sea, which on occasions can be quite rough.  Blue-tinged icebergs idly floated past as the ship sailed on towards Elephant Island, an ice-covered mountainous island off the coast of Antarctica in the outer reaches the South Shetland Islands in the Southern Ocean.  The island is most noted as the desolate refuge of Shackleton and his crew of twenty-eight in 1916 following the loss of their ship Endurance to the Weddell Sea ice.

Eventually, Ann's trip took her to the Antarctic Peninsula proper, engendering a feeling of relief and achievement at having reached that continent. Again, there was the opportunity to photograph yet more penguins and more glaciers.

One of the highlights of a visit to the Antarctic, perhaps it could be called a ‘hot-spot’, is the caldera of Deception Island. This is a magical place.  Recent volcanic activity has indeed kept the water hot.

Returning northwards across the Drake Passage, Ann was able to see the lowering hulk of Cape Horn. She observed that, although the sea was rough, the spray had not obscured the southernmost tip of the American Continent.

This was a lively talk, given with great enthusiasm by Ann, who clearly enjoys her travels enormously.

Finally, in a frivolous humorous competition set up by Ann, long-standing member Dennis Ward carried off the small prize by correctly identifying the mineral from which her necklace was made: ‘out of this world – tektite’. Well done, Dennis.

                                                                                                 Peter Webster

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Reconstructing the Early Human History of Britain.

Professor Chris Stringer, of the Palaeontology Department of the Natural History Museum, gave the June evening lecture.  The project with which he is involved is the ‘Ancient Human Occupation of Britain’. The second phase of the Ancient Human Occupation of Britain project (AHOB) is funded to run until 2010, thanks to a grant by the Leverhulme Trust. The project, which started in October 2001, has made groundbreaking discoveries dating human occupation of Britain back as far as 700,000 years. Phase two of the AHOB project (AHOB2) will continue to add data on the earliest human colonisations of Britain, but the project will also carry out more comparative studies in continental Europe.

Chris began by discussing the fact that early humans were present in Africa some six million years ago. Homo erectus began to migrate some 1.8 million years ago, leaving first for the tropics and then moving northwards.  From the neck downwards their appearance was ‘normal’ but they were exceedingly primitive above the neck. They could however make tools.

They reached Europe 0.8 mya, their remains having been found in Spain, and they were considerably more advanced than their African ancestors. To migrate even further north must have required further adaptations, for example those of clothing and shelter.

These early ‘Britons’ had to cope with considerable variations and extreme changes of climate, but apparently they failed to do so on a number of occasions and as a consequence they died out completely. There was a land bridge between France and England, so periodic re-populations took place.

Chris commented on Boxgrove, our excellent local Sussex archaeological site, where the tibia of Boxgrove Man was found. At 6 ft. tall and 90 kg he was a large strong man. In his era, flint tools were in use. Unfortunately, Boxgrove Man was wiped out by a glacial episode.

At 0.4 mya, Swanscombe Man appeared, probably an early Neanderthal person. By now the Channel had formed and widened, such that migration between England and France would have been more difficult.

There is then an absence of human remains in the record until 60 kya, although many animal remains have been found, the species ranging from hippos to reindeer, wolves and bears.

At 60 kya the Neanderthals returned, presumably having adapted adequately to cope with the cold winters. Their ability to adapt is supported by a body of evidence. However at 35 kya, the Neanderthals came face to face with modern humans, raising the question, what happened to the original inhabitants? Chris described the Neanderthals as ‘good at what they did - but not great innovators’.

The work by the AHOB continues, utilising many modern techniques such as CT scanning and DNA analyses.

As always, after the formal lecture, numerous questions were raised, and fielded by Chris. Again we have to give thanks to an eminent speaker involved in important research who has been prepared to give up his time to give an excellent and interesting talk to the club.

Peter Webster

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Widgiemoolthalite

It’s a mineral. And so are adamite, eveite, boggsite, niggliite, maxwellite and murdochite, ferrowyllieite, plumbogummite and, of course, gordonite. (Find them on www.mindat.org/mineralindex.php.) Nick Park’s Plasticene Pals have found others:

‘Grandviewite,’ said Wallace to Gromit.

‘Tiptopite, old friend, I should say.

Goldquarryite beckons us, Gromit,

There’s treasureite coming our way:

 

‘It’s Archerite time on the radio

(The Simpsonite’s been on TV);

There’s pigeonite pie in the oven

And Pringleite crispies for tea;

 

‘For breakfast, Marumoite, Gromit,

Spread thickly on  Wensleydale cheese.

Macdonaldite? Never, eh, Gromit?

We’re proudite, and eat what we please.’

 

                                         Gordon Judge

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In Mary Anning’s footsteps

In 1811, on the shore near her home town of Lyme Regis, Mary Anning and her brother found the skull of what was subsequently recognised and named as an ichthyosaur. In 2004, the vertebrae of another ichthyosaur were spotted on Charmouth beach by Dr. Paul Davis. Its ‘half-skeleton’ was cleaned up at the Natural History Museum before being returned to Dorset in May this year for a year-long tour of local venues, starting at the Marine Theatre in Lyme Regis.

 

Did you see me in the theatre, in my solo stand-up gig?

I’m too modest, or I’d tell you that I went down really big.

If you missed me, not to worry: when next time you’re down this way

Just ask anyone – they’ll tell you I’m on tour until next May.

 

An ichthyosaur on tour? The reason is because

My vertebrae had surfaced on the beach. Here’s how it was.

The eagle-eyed Paul Davis, as he scoured the rocks near Lyme

In Mary Anning’s footsteps, recognised me just in time.

 

He’d spotted, on the foreshore, a row of bumps, aligned.

“An ichthyosaur, I reckon; what a very lucky find!” ^*

I soon was excavated, translocated and, with care,

Delivered to the NHM.  And there they laid me bare –

 

Chipped away my stony casing till my bones were clearly seen,

And my ichthyosaurial remnants were all scrubbed up squeaky clean.

And so I’ve gone on tour; but it won’t go to my head

For I’m only half a skeleton, and very, very, dead!

 

NOTE * It is possible that other, less poetic, language was used here

 

                                                                                       Gordon Judge

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Off the scale (by Dr. Ted Nield, first published in Geoscientist 17 - 6 June 2007, p2. Reproduced by permission of The Geological Society of London

After the English Channel quake of April 28, Ted Nield bewails the popular persistence of "the Richter Scale"

One of the things that separates scientists from journalists is this. Scientists, like all academics, go through life learning more and more about less and less. We hacks on the other hand tend to learn more and more about more and more - and then to forget it all. Finding ourselves daily adrift in a sea of intellectual uncertainty, buffeted by a perfect storm of information from all points of the compass, we have tendency to cling desperately to things that we think we know. One of those things is "the Richter Scale".

Every journalist has written "An earthquake measuring 7.8 on the Richter Scale has struck the island of Sumatra...." at some stage in their career, and a week hardly passes when you cannot read it somewhere. But why?

Because first of all, it's wrong. Seismologists no longer use the Richter Scale, defined in 1935 by the famous Californian nudist Charles F Richter (1900-1985) and Beno Gutenberg (1889-1960) of the California Institute of Technology (CIT). Although the idea of a logarithmic magnitude scale was first developed by Richter and Gutenberg, it was designed for measuring the size of earthquakes in southern California, and it used fairly high-frequency data from nearby seismographs. What eventually became known as the "Richter" magnitude was originally called "Local Magnitude" or M_L. As more seismographs were set up around the world, it soon became apparent Richter's method was strictly valid only within certain frequency and distance ranges. Like many things from California, it possessed certain magic characteristics.

New magnitude scales that extended Richter & Gutenberg's original idea were developed as the number of recording stations worldwide increased. These include body-wave magnitude (Mb) and surface wave magnitude (Ms). Each is valid over a particular range of frequency and type of signal, and within its own parameters is equivalent to "Richter" magnitude. But because of the limitations of all three (especially the tendency to become saturated at high magnitudes, so that very large events cannot be easily distinguished) a more uniformly applicable magnitude scale, known as moment magnitude, was developed in 1979 by two other CIT scientists, Tom Hanks and Hiroo Kanamori. For very large earthquakes, Mw gives the most reliable estimate of earthquake size, and this is the measure that is always misreported as "the Richter Scale".OK - so much for the science bit. But ask yourself this - even if scientists did still use Richter, what real information would be conveyed by mentioning him? Forecasters may speak of Celsius and Fahrenheit, but only because there is a choice.  Moreover, being correct and writing "An earthquake of Magnitude 7.8 has struck the island of Sumatra" is four words shorter. The chance to achieve correctness and concision at the same time ought to be welcomed by journalists everywhere - if only because the two coincide so rarely. Lastly, by not using the word "scale" we would avoid fostering the assumption, almost as mistaken as it is universal, that "the Richter Scale" has a top. (Or for that matter, a bottom. If this confuses you, just remember that the saying: "logarithmic plots are a device of the devil" is attributed to Richter.)

It is my theory that my fellow journalists cannot resist saying "on the Richter Scale" because like the epic poets, they rely heavily on repeated stock phrases - we call them clichés. Moreover, the public expects it. We are seeing a conspiracy - between journalists wishing to sound knowledgeable, and the public, which likes to flatter itself that it knows something, especially when it doesn't.

Richter's only remaining function, therefore, is to provide a beacon of false hope amid the choppy waters of ignorance in which we float. And for that reason, I fear that we shall go on clinging to him.

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Seismic Surveying and 3-D Modelling

An A.G.M. for any organisation is a necessary evil, and mercifully they make only annual appearances, rather like tax-returns and Halloween.  However, the post-business slot for the May 2007 meeting was memorably taken up by a fascinating talk by Helen Debenham, describing her involvement in the process of seismic surveying undertaken by CGGVeritas.

Her talk fell approximately into three parts. Firstly, she described the acquisition of the raw data. Her particular interest has been marine. The presentation began with some pretty pictures of half a dozen bright red 'boats' (the purists really wanted 'ships' but never mind!), floating on an azure duckpond-calm sea. The names of these boats all included 'Viking', appropriate given that much of their deployment appears to be in the North Sea, and that the crew members at the sharp end are Norwegian. Then more details began to emerge. These vessels are towing a complex network of cables bearing rather expensive equipment. The attachment is not a simple line streaming behind the boat but a fan of numerous cables, which as far as possible are maintained in parallel station, and some twelve km long. Not surprisingly there are difficulties in towing this arrangement, such as interacting with fishing boats occupying the same waters and stationary oil-rigs, not to mention large waves. However, whilst maintaining an accurate and carefully monitored track over the sea-bed, the survey team blast-off with the double-acting 'air-guns', and retrieve the reflected sound signals on multiple hydrophones. Almost with regret, and with a touch of the Guy Fawkes, Helen noted that the use of dynamite to produce a sharp crisp signal was now considered environmentally unacceptable!  However, apropos that, she did note that a crew member is on watch in the bows looking out for whales.  What happens to the sharks who have taken a fancy to the cables was not recorded.

Helen then discussed some of the Physics appertaining to seismic exploration, which basically involves the velocity of sound in the various media, and reflection and refraction at the interfaces of the different rocks.

She then moved on to that part of the process in which she is directly involved. The seismic data is attacked by banks of exceedingly powerful processors. Clearly this operation is exceedingly complex, given the number of variables and the sheer quantity of data, but eventually a three-dimensional model of the underlying geology can be produced. Quite disarmingly, Helen played down the role of herself as a geologist, and her own interventions in the process. When pressed during questioning however, she admitted that, despite there being banks of steaming processors churning through the data, for successful modelling there remained scope for the 'black arts' on the part of the geologist. After all, even the most sophisticated software will fail with poor data, remember the old adage 'garbage in, garbage out'.

The presentation ended with her pièce de résistance, a beautiful image of her brainchild, a 3-D model, of some 1000 sq. km., relating to the geology of the North Sea.

Helen delivered a lively, entertaining and informative talk. She is clearly on top of her game and I can now see why she is so perceptive during the questioning of visiting speakers, and the way she ferrets information from them. In this talk she skilfully conveyed a wealth of information, interspersed with witty and amusing asides: we even glimpsed her boy-friend!  Question time was only ended by the 9.30 bell, a fine indicator as to the quality of the lecture and a compliment to the speaker.

She was aided and abetted by her colleague Khalid, whose leaning is towards land-based work. We had been shown images of enormous trucks dropping large chunks of metal onto the desert sand. Of course, it is less convenient making seismic surveys on land, having to work around inconveniences such as houses and rivers.

So, far from being a time-filling adjunct to the A.G.M., Helen's thoroughly entertaining contribution was most certainly worthy of a full-blown slot. Sincere thanks are due to Helen and Khalid for the evening, and to her company, CGGVeritas, for permitting her to describe her work.

                                                                                                 Peter Webster

 

For interest and background information, Google searches on 'seismic surveys North Sea' produces a wealth of background information, indeed about a million pages are available. www.cggVeritas.com is informative regarding the company. For instance, there are images of some of aforesaid smart boats and the equipment. (And they are recruiting at the time of writing!).

A point which Helen touched on was the possible effects on whales of the sharp explosive sounds used in survey work. Googling 'cetacean seismic survey North Sea' produces some interesting observations and papers on the behaviour of Cetaceans in the vicinity of survey ships.

www.acousticecology.org/oceanairgunexecsumm.html discusses in some detail the available evidence of the effects on Cetaceans.

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Field Trip - Yorkshire March 31 – April 3  2007 - Led by Professor Rory Mortimore

The trip was a great success, and was enjoyed by all those who went on it. We arrived on Saturday to be confronted by our hotel which was literally a castle, and run by nuns. Rory met us at six and we had an introductory talk to the area in which we discussed the itinerary for the trip and the geology we would be seeing. Sunday started early with a walk through town, to get from the car park to East Cliff, fully kitted-up in our gear getting very odd looks from the tourists. We were collecting from the upper lias in the Toarcian and Whitbian. Disappointingly part of the exposure is covered by sea defences but further down the beach the exposure is accessible; the wave-cut platform also yielded many ammonite nodules; also to be found were many belemnites and lingula.

We walked along to the exposure of the dogger which marks the transition between marine and deltaic sediments. It has a high iron content (25%) and used to be mined. It is made up of shell fragments and ooliths; there were many burrows at the bottom of the dogger into the lias, which were infilled with the dogger. The base of the dogger contains pieces of the lias showing that it is an unconformity. Above the dogger are the Middle Jurassic deltaic deposits. These consist of non-marine sand and mudstones but with some thin marine beds. The deltaic sandstones show many infilled channels and these often contain tree trunks.

The cliffs at Whitby also contain jet, which is identifiable from coal by the fact that when you rub it on something it leaves a brown streak instead of a black one. We walked back along the cliff to Whitby where we had a pub lunch. Then we crossed town again and went on to West Beach. As the strata dip to the east and there is a fault under the river which has caused the east side to be pushed up and the west side down, the lias isn’t exposed on West Beach. We looked in much closer detail at the deltaic sediments. You can see roots of equisetums that have been infilled. The channels all flow towards where the North Sea now is. The sediment shows much evidence of dinoturbidity.

We walked along West Beach to where a glacial valley comes down to the sea; the valley has been infilled with glacial till and as a result that section of the cliff is subject to much subsidence which the local council is failing miserably at sorting out. The authorities having spent millions a few years ago on cutting back the cliff and installing rock-drains, the cliff is still slipping. By this point the tide was coming in rapidly and we made our way back to the cars.

As it was quite early in the day we visited Whitby Museum, which has an amazing collection of ammonites all laid out in stratigraphical order and they are often the holotype specimen. There are also other displays on the history of Whitby and its whaling times. On Monday we went inland to study the glaciation of the North Yorkshire Moors. We started at Danby Beacon but unfortunately the visibility was next to nothing, so we couldn’t see the amazing view we were supposed to. We then drove down the side of the hill and made it to about half-way down when the visibility cleared and we got half of the promised amazing view. This was over Eskdale and two big glacial valleys which are called the Fry-Ups, which was spectacular. Part of the point of the day was for us to make up our minds about whether we thought Eskdale had been glaciated or a glacial lake during the last ice age (Devensian). In 1905 the area was surveyed and it was thought then that Eskdale was a glacial lake but more recent analysis points toward there being ice inside the valley. We moved along to Lealholm to look at the moraine, which according to the 1905 interpretation would have contained the glacial lake. From Lealholm you can also see Crunkly Gill which is where the Esk leaves the main valley and has cut a 300ft ravine into the next hill.

There is also a small horseshoe-shaped valley which drains from both ends and has no drainage system above it. This shows that it must have been formed under a glacier, the pressure of the ice above makes the water flow uphill, showing that Eskdale must have been glaciated at some point.

We then went to Egton Banks to look at the Kame Terraces, which are formed along the sides of retreating glaciers. They show that Eskdale definitely had ice in it. These things led us to the decision that Eskdale was glaciated. Egton Banks is where the Cleveland Dyke cuts through the liassic shales. The dyke was formed when America and Scotland broke apart. It is tholeiitic basalt. The shale surrounding the intrusion has been baked and the crystals within it have fused.

We lunched in Glaisdale, and watched a steam train leave the station. After lunch we went to Grosmont to look at the river cliff there. One of the main tributaries of the Esk has carved through the shale presenting an exposure of liassic shales and oolitic ironstone. This was the only fossil-oriented part of the day, with many brachiopods and bivalves to be found and a few ammonites. We then went back up on to the high moor at Murk Mire, to look at more under-glacier river structures. These drained in the opposite direction to the modern drainage system. Ladybridge Slack and Randymire Valley drain towards Newtondale and the Vale of Pickering. We then returned to Danby beacon to see the view we missed in the morning. By this point we were losing light so we returned home.

Tuesday we went to look at the Speeton Clay and the red chalk. Access to the beach is at Reeton. The Speeton Clay is grey with light and dark bands; the light bands contain large amounts of volcanic dust and the dark are marine sediments. The clay is isoclinally folded and contains heteromorphy ammonites in their original shells and lots of belemnites. It is lower cretaceous, roughly the same age as the lower and upper greensand. The Speeton Clay is subdivided into A,B,C,D, oldest to youngest, top to bottom, which is the wrong way round, but it was done in 1889 so wasn’t considered wrong and now can’t be changed.  It is characterised by belemnites, some of them come from the north (Boreal Sea) and some come from the south (Tethys Sea):

Neohibilites(Tethys)

Praeoxyteuthis, Aulacoteuthis, oxyteuthis (Boreal)

Hibolites (Tethys)

Acroteuthis (Boreal)

The red chalk is the base unit of the cretaceous chalk but only occurs north of The Wash and contains many belemnites (neohibilites minimus). Then there are the grey nodular chalks and the white chalk (Cenomanian) which contain paramoudra flints. We walked down the beach quickly to get to the red chalk where we collected lots of belemnites, and then walked slowly back, collecting from the Speeton Clay as we made our way back to the cars. As it was very windy and we had the long drive home ahead of us, we were all off the beach by three o’clock. The trip was very good and in my opinion the best the Club has run in a long time. I hope this opinion was shared by all who were on it.

                                                                                                     Sam Reese

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Water for thought

Recent observations suggest that major changes in parts of the ice sheets are taking place over time scales of a few years to decades. The great ice sheets covering Antarctica and Greenland contain about 80% of the Earth’s fresh water and cover 10% of the World’s land surface. If they were to melt completely, global sea levels would rise some seventy metres - rather more than Horsham’s highest point above sea level!

                                                     (Gleaned from Geoscientist, A