Letters

This page has been created to facilitate rapid and timely interchange of opinion. Each month (space permitting) a selection of these letters will be published in Geoscientist , the colour monthly magazine of the Society Fellowship.

Correspondence strings are listed in the order that they are begun, the most recent string at the top. Within each string, letters are listed with the first letter of the string at the top, and subsequent letters below.

This page contains letters from the current year.  The archive of letters from previous years are accessible by clicking the links to the left.

If you wish to express an opinion, please email the Editor. Letters should be as short as possible, preferably c.300 words long or fewer. You may also write to:

Dr Ted Nield, Editor, Geoscientist, c/o The Geological Society, Burlington House, Piccadilly, London W1J 0BG.

• Please note that letters will be edited for publication. This particularly applies to versions  printed in the magazine.  The Editor reserves the right not to publish letters, at his discretion. Writers should submit their letters electronically to ensure rapid publication. All views expressed below are the responsibility of their authors alone.TN

UK Olympic no-show explained

From Kevin Stephen * (Rec'd & Pub'd  15 May 2012)

Sir, I was fascinated to read Dwain Eldred extolling the virtues of the IESO annual Earth Science Competition for secondary science students (Geoscientist 22.04 May 2012). The lack of a UK team at this event is a great shame, but is the result of three fundamental contributory factors.

• First, the syllabus for the IESO has its roots in SE Asia where Earth science education is taken seriously and geology, geophysics, meteorology, oceanography, astronomy, and environmental science are taught as a coherent unit. Unfortunately Earth Science is taught as an addendum in many UK schools and even this cursory coverage is at risk.
• Second, to enter a viable team requires that a national competition identify the very best students before the UK could compete on an even footing. This would need organisational support from the Geological Society - the Institute of Physics, Royal Society of CHemistry and Institute of Biology oversee team-selection for other 'science Olympiads'.
• Finally, the small matter of funding a UK team's participation would need resolving.

Unlike our athletic colleagues competing in London this summer, alas our outstanding UK Earth Science students will not have the opportunity to be Olympians for some time to come.

* Altrincham Boys Grammar School.

Worth a Wager

From Geoff Glasby (Rec'd & Pub'd 15 May 2012)

Sir, I was very surprised to read in Everest - the best writing and pictures of seventy years of human endeavour  (Edited by Peter Gilman, Foreword by Sir Edmund Hillary), that three climbers reached an altitutude of 28,100ft - 8565m) on Everest in 1933 ('My Nastiest moment', Jack Longford, pp.42-46).

I did my Part II in Chemistry at Oxford in 1966 in the Department of Geology at Oxford University, under the supervision of Dr Norman Snelling, where Lawrence Wager was Professor. As I understood it, Wager made a solo climb on Everest to 28,100ft in 1933 but was obliged to descend after facing a large slab of rock about 2m high with a very smooth surface and no suitable handgrips - which he considered unclimbable. He used his remaining time at this extreme altitude to collect geological samples, which were later stored at the Geological Museum in Oxford and ignored until the early 1950s when they were found and studied in detail. The claim that Jack Longland was also at 28,100ft on Everest during this expedition therefore seems to be mistaken.

There is incidently, an excellent group photograph showing Jack Longland, Percy Wynn Harris and Lawrence Wager together with eight sherpas at high altitude on Everest. Wager himself was, of course, a Yorkshireman who learned the craft of climbing in the Yorkshire Dales. He died suddenly aged 61 while I was doing my Part II in Chemistry in the Geology. It was a massive loss. I myself could not recognise Wager from his 1933 photograph. He had clearly burned the candle at both ends!

Micropalaeontological woe (continued)

Mircopalaeontologists - stop whining and start reinventing!

From Cornelia Kohler  (Rec'd & Pub'd 9 May 2012)

Sir, recently the self-promotion of micropalaeontology has figured large in Geoscientist. I agree that it is a disappearing core discipline and that it has important applications. But no one seems to ask why it is losing its significance. Unlike other disciplines, which are becoming more important especially in the petroleum industry, biostratigraphy has failed to enter the 21st Century. I strongly believe it needs to reinvent itself and free itself from the past. With so many passionate thinkers out there, I am sure this approach should not be a problem. But at the moment all that is discussed is “saving” the old ways. That is not the best for this essential discipline. At wellsite, for example, 21st century technologies are being more widely used than ever before.

By ignoring its shortcomings, as it has done for long time, this discipline will further lose importance and appeal. There are sadly very few pioneers left and these are usually heavily criticised. So, I plead to micropalaeontologists: stop patting each other on the back, stop thinking it is a perfect discipline and start reinventing yourselves – geology needs you!

Micropalaeontology not helped by being insulted

From Rex Harland (Rec’d & Pub’d 8 May 2012)

Sir, I would like to endorse the article on the near demise of micropalaeontologists (Soapbox, Geoscientist, 22.4, May 2012). It is certainly the case that the number of micropalaeontologists has diminished over recent years, with retirements and the lack of training for the young. I speak from experience, in being part of the second intake of the MSc (Palynology) course at Sheffield in 1966, having taught part of the same course (1994-2003), been the External Examiner to the University College of Wales, Aberystwyth (1990-1994) and now Guest Professor of Marine Micropalaeontology at the University of Gothenburg, Sweden.

The problem was foreseen and discussed in the 90s, in various informal groups and within NERC reviews, but without any strategic planning forthcoming. The fault lays with the academic funding bodies and industry who both failed to realise the importance of the science per se and its application to the discovery and recovery of hydrocarbons and the associated generation of economic wealth. Recently the use of micropalaeontology has become an important tool in documenting climate change with major implications for the future well being of our planet.

Unfortunately part of the problem lies with a perception that micropalaeontologists are ‘bug pickers’. This is both untrue, demeaning and a slur on the profession. Micropalaeontologists use their knowledge to explore evolution, from the earliest beginnings of eukaryotic life, and to detail the history of the world ocean to its present worrying state. In so doing new statistical techniques, DNA based phylogenetic analysis, biochemical methodology and detailed morphological studies are yielding exciting results, as a perusal of the abstract volumes of any recent micropalaeontological conference will attest.

There is a need to ensure a continuity of university training to maintain micropalaeontology as a healthy part of the Earth Science curriculum. With the demise of certain ‘centres of excellence’ there is a need to provide new generations with the skills that will be in demand to solve problems within hydrocarbon exploration, resource management and global climate change. Centres of excellence usually grow around a core of talented personnel who can provide basic training but also inspire innovative research. Such people need to be identified and nurtured whilst still young so that the rest follows.

Not me, guv

From Alan Lord (Rec'd & Pub'd 7 March 2012)

Sir, While I appreciate Dr Cordey's support for the cause of micropalaeontology (see below), I must beg him to get his facts straight. I left UCL in 2006, at which time the MSc programme in Micropalaeontology was healthy.  It was other folk who subsequently closed it!

Drudge dread

From Griff Cordey (Rec’d & Pub’d 6 March 2012)

Sir, I was delighted to see Alan Lord making the case for the ‘disappearing’ micropalaeontologist
(Geoscientist 22.2 p6). He is well qualified to do so as he had the misfortune of having to preside over the closure of University College London’s micropalaeontology course, first established in 1959 under Tom Barnard. I was one of the first intake.

The importance of operational micropalaeo to drilling operations has long been recognised and with directional drilling a prominent feature of modern drilling practice, it has become even more important.  I suspect that the oil majors have some of their own in-house expertise in this field. But smaller companies probably rely on consultants for this service.

Alan’s plea to restore teaching of this subject in the UK is timely, and one hopes that the Birmingham University initiative will be a resounding success and that industry will contribute to making it so.  However, I would urge those eager to raise enthusiasm among the young not to follow our Fellowship magazine’s choice of terminology.

• Father: “Well son, what are you going to do when you graduate?”
• Son; “I’m going to be a harmless bug-picking drudge!”

Know your limits!

From Robin Hazell (Rec’d & Pub’d 10 April 2012)

Sir, Years ago John Wright (Open University), in this very magazine, averred that ‘sustainable development’ is a contradiction in terms. More recently, Martin Lack and Geoff Glasby (see below for Glasby) are to be congratulated on taking up the problem of ‘exponential’ growth. I hope our own growth - in awareness and debate - will follow a similar path.

Short term development in any field, natural or human is, and always has been, inevitable; but in the seriously long term, none of the many waves of development has ever been sustained. Living forms were cropped by thermal events in mass extinctions, but recovered. Later, human activity cut in. Populations waxed and waned, but recovered. The last few thousand years have seen the birth, zenith and collapse of organisations and empires, together with the collapse of the stability thus engendered. Now, a great wave has been generated by the population explosion and the inevitable plundering of finite resources, It is climbing ever more steeply and we are all clinging precariously to the wave. Many consider that the point of no return has been reached.

This would be inevitable if growth curves were truly exponential. The good news is that they are not. They are more akin to a series of skewed sine curves; with time, the magnitude of these curves increases. If some clever fellow could line them up, curves plotted through the crests and troughs would show an upward gradient, though much more gentle than that of the great wave we are now ascending.

Although human and higher forms of life will be drastically thinned out when, by plague, famine or war, the present steep wave topples and collapses, some forms of life native to this planet - or extra terrestrial - will survive. With them will survive a chunk of our store of knowledge, and possibly even a few fragments of wisdom.

The term ‘metaphysical’ could be taken to mean changes resulting from the action of heat and pressure on our own physical state. Some of us could then be perched on clouds (if any have not been dissipated by a thermal event) plucking celestial harps. We can fervently hope that at least a few will be members of our Geological Society, closely observing cataclysmic events while recording and - with no little heat - discussing them. To enliven eternity we will, with celestial hammers, take desultory swipes at passing meteorites.

I am a grumpy old git, but if someone will tell me I am wrong I will turn up my toes with a smile on my face.

From Geoff Glasby (Rec'd & Pub'd 13 February 2012)

Sir, In Geoscientist (21.11) Martin Lack pointed out that we live in a finite world and commented on the limitations of exponential growth and suggests that we should should act accordingly to control the growth rate in order ensure that we do not exceed certain limits in the future. I have recently written a lengthy paper on the inevitability of continuing environmental degradation (Glasby 2010) and stongly endorse this view.

According to my calculations (Glasby 2010), the world population will increase from 6272 in 2000 to 8400 in 2100 based on an average increase in world population of 0.92% p.a.

Per capita GDP will increase from 19,532 dollars to 105,432 dollars at a rate of increase of 2.83 percent p.a.

World G.D.P. will increase from $ 164,885 to $ 627,067 at a rate of increase of 3.12% p.a. and total wealth created will increase from $ 5877 trillion  to $ 22,972 trillion in 2100. In addition, atmospheric CO₂ will increase from 367 ppm in 2000 to 513 ppm in 2100.

These potential increases in human consumption and atmospheric CO₂ contents look formidable.

It would appear to me that, if these increases take place on the scale suggested, they will greatly undermine the atractiveness of Planet Earth as a place to live. Perhaps we should do something about it!

Reference

Glasby, G.P. 2010. The inevitability of continuing environmental degradation. Advances in Energy Research, Volume 1, Chapter 5. Nova Science Publishers, Inc., pp. 183-201.

A cyclepath writes...

From Professor Richard Selley (Rec'd & Pub'd 13 February 2012)

Sir, Re. Cycle pathology: Who was it who said ‘All sedimentation is cyclic, some is more cyclic than others’?

Robin Bailey replies: (Rec'd & Pub'd 10 April 2012)

Sir, I don't know who said it either, but he/she perhaps ought to have said: "No sedimentation is cyclic, but some is more cyclic than others"!

Insensitive – and unwise

From Jeremy Daines* (Rec'd & Pub'd 4 April 2011)

Sir, Like Mr Isles, I cannot wait for the “safer issues of Geoscientist” and trust that Chartered Engineering Geologist, Mr Steve Branch will be able to cope with the onerous workload of vetting every image against the laws & regulations that Mr Isles kindly listed.

I wasn’t aware that Geoscientist had a remit to ensure total compliance with all such regulations; but at least that’s been cleared-up, thanks to Mr Isles’ letter in Geoscientist 22.3 p23 (below).

Now that Geoscientist has processes in place and is, I assume, fully compliant; I’d like to invite Mr Isles to provide the readership with what he, in his capacity as MPA President, The Institute of Quarrying, has done to ensure people don’t put themselves at risk of the moderately competent Branscombe Mudstone Formation, in the future? I hope the person in the offending image survived?

* Managing Director, Oleum Khaos Limited

From Martin Isles*

Sir, I was considerably saddened to see the photo on page 7 of the Dec2011/Jan2012 issue depicting a person crouching adjacent to the vertical sidewall at the base of an unsupported trench of at least 4 metres depth. At best, what is shown is plainly bad practice; at worst your journal is effectively condoning a potentially life-threatening situation.

With the long sad history of so many deaths and major injuries arising from trench collapses, for ‘Geoscientist’ to print this image without any warning or comment is irresponsible and unprofessional. As a geologist-by-training, to see my profession’s otherwise excellent magazine failing to prevent the publication of such an image demonstrates clearly that there are fundamental lessons still to be learnt.

The law on such issues reflects what should be simple common sense, i.e. any such work must be risk assessed by a competent person to ensure a safe system of work to control the risk of trench collapse. As an absolute minimum, for the protection of themselves and others, geoscience companies and individual geo-scientists should be familiar with at least the basic legislation, viz:

• Health and Safety at Work etc Act 1974, Sections 2 & 7
• Management of Health and Safety at Work Regulations 1999, Reg.3
• Construction (Design and Management) Regulations 2007, Reg.31

The offending image shows the reddish-brown Upper Triassic Branscombe Mudstone Formation with its green-grey reduction interbeds. In geotechnical terms, these lithologies might reasonably be described as moderately competent. But a journal with the professional standing and responsibilities of ‘Geoscientist’ should take much more care to ensure that such images – editorially of interest for scientific reasons – do not depict examples of operational bad practice. In short, procedures should be in place to ensure that every such image in every issue is vetted by a person with competence in practical health and safety. In certain non-UK circumstances where operational practice is to a lower standard, then an editorial comment to this effect would be appropriate.

I look forward to safer issues of ‘Geoscientist’ in the future.

* Director, Health & Safety, MPA President, The Institute of Quarrying

From Chris Jerram (Rec'd & Pub'd 8 December 2011)

Sir, I am sure I am not the first, and almost certainly I will not be the last, to make comment on the photograph accompanying the Glimpses of the past (Geoscientist 21.11). In a year when the owner of a ground investigation company was convicted of corporate manslaughter and the unfortunate victim was a Fellow of the Society, it is surely the height of insensitivity and lack of common sense that the picture shows a geologist crouching in front of a vertical face that must be well over 3m high.

The defence might be that the exposed strata is competent rock and the superficials have been battered back (slightly). However, what sort of example does it send out to members of our profession who now think that the Geological Society give tacit approval to activities such as those depicted in the photograph?

GRM emphasise to all of our staff that entry into un-shored excavations below 1.2m should never be attempted. The excavation depicted could well be perfectly safe, but a young geologist taking a casual look at the magazine would probably be understandably confused by the apparent double standards and decide that our H&S advice is flawed.

Ian Plimer ‘confused on fundamental issues’

From Colin Summerhayes (Rec’d & Pub’d 23 March 2012)

Sir, The March issue of Geoscientist contained a review of “How to Get Expelled from School: a Guide to Climate Change for Pupils, Parents and Punters” (Connor Court, 2011), the latest outpouring from the pen of Australian economic geologist Professor Ian Plimer, an Honorary Fellow of the Society. That book is a sequel to his 500-page blockbuster “Heaven and Earth: Global Warming – the Missing Science” (Connor Court, 2009).

Professor Plimer is a member of the Australian Climate Science Coalition, a group that is highly sceptical of anthropogenic global warming (AGW). He makes it plain in his books and in videos on the web that his stance is profoundly anti-environmentalist, and both his books give the impression that he might be proud to be thought of as a crusader against the concept of AGW.

I find Plimer’s texts difficult to read because he seems confused on fundamental issues. He is happy to tell us on p.126 that carbon dioxide is a greenhouse gas that helps to keep the planet habitable, on p.127 that there is no evidence that human emissions of carbon dioxide drive climate change, but on p.128 that if the current levels of CO₂ doubled temperatures would increase by 0.2°C. Which is it to be? In any case, the vast majority of climate scientists disagree that doubling CO₂ would have so little an effect. Even sceptic Richard Lindzen of MIT would have a doubling of CO₂ raise temperature by about 1°C, while NASA’s Jim Hansen says it will be 3°C, based on paleoclimatic evidence. Who is advising Plimer, one wonders?

“The story of planet Earth is a marvellous chronicle written in stone.” Plimer writes. “The only way to understand climate is to read the rocks because the present derives from the past.” True. So in that case why does his latest book gloss over the Paleocene-Eocene Thermal Maximum, when a massive injection of carbon into the atmosphere caused it to warm by 5-6°C, and the enhanced carbon dioxide concentration in the ocean caused it to become slightly less alkaline thus raising the carbonate compensation depth and removing carbonate oozes and calcareous benthic foraminifera from the deep ocean?

What’s more that event lasted, the geological record tells us, for 100,000 years before things returned to normal (see October 2011 issue of National Geographic for a general description). Isn’t this close to an analogue for what is happening today, as the Geological Society of London’s climate change statement suggests? Doesn’t it contain warnings as to our possible future if emissions increase? So why does he ignore its implications? Perhaps it is one of those ‘Inconvenient Truths’ for the anti-environmentalist Plimer manifesto. Could we ask him to enlighten us with his views?

Models need data - time to catch the wind?

From Chris King (Rec’d * Pub’d 13 March 2012)

Sir, The brave new 3D world envisaged by BGS (Geoscientist 22.02 March 2012, p. 19) is a tremendous initiative with many obvious benefits to academic, governmental and commercial interests. 'Traditional' geological mapping relied largely on data from the land surface and excavations or mines, with limited subsurface input required from other sources.

3D modelling is however dependent on the accurate recording and interpretation of large quantities of subsurface data, much of which is derived from commercial GI (Ground Investigation) reports. Unless a proactive approach to acquisition of data from these sources is adopted, in collaboration with the geotechnical industry, much relevant information will be lost or remain inaccessible. This needs to be carried out in 'real time' so that relevant sample/core material can be reviewed where appropriate. Data recorded on GI borehole logs are based on standards designed for geotechnical purposes, and can often fail to provide critical information relevant to stratigraphic classification.

A key example is the current 'explosion' in wind farm projects, both onshore and offshore. Why is there no integrated scheme to ensure that the geological data resulting from these is adequately assessed and recorded ? It's a one-time opportunity in many areas. When the GI reports finally get into the public domain it's likely too late to ask to see a critical core!

Modelling needs modellers, but modellers need data. To adapt Thomas Huxley’s famous dictum: 'it only takes one ugly borehole to destroy a beautiful model'.

Expulsion letter

From John Veevers (Rec’d & pub’d 12 March 2012)

Sir, Reading Julian Vearncombe’s review of Ian Plimer’s How to get expelled from school … (Geoscientist 22.02, March 2012), I found myself checking the cover to see that I hadn’t picked up The Spectator or some other political magazine.

With support from such political leaders as John Howard and Vaclav Klaus, Plimer doesn’t need to worry about the science. In quality journals, polemics are debated by both sides so I expected to find a second, dissenting, view here. But no, get expelled came across as an everyday book on geoscience, without any hint of heresy.

Is this now policy? And if so, may we soon expect reviews of books on creation science or astrology?

Editor writes:  We have in the past run many reviews of books purporting to be geoscientific in content, including those espousing "creation science".  We think that in this case Geoscientist readers are savvy enough to judge for themselves whether they wish to purchase a copy of Professor Plimer's latest.

Restore Rig 20's missing footage!

From David Jutson (Rec'd & Pub'd  7 March)

Sir, I have a copy of the missing section of the Rig 20 blowout film as an an MP3 file. I use it when giving my Applied Biostratigraphy course at the University of Bonn.  I would be happy to supply it to Peter Jones or other interested parties. The clip I have is just under 8Mb and has a poor soundtrack, but the drillstring flying out of the hole is, nevertheless, terrifying!!

From Myles Bowen (Rec'd  & Pub'd 6 March 2012)

Sir, I would like to support Peter Jones' plea for the publication of the original footage of Rig 20. Personally I have never seen the film, although I would very much have liked to. My reason for writing this letter is that very few geoscientists, even those in the oil/gas industry, have ever witnessed a blow-out at close quarters. I have been lucky enough to witness two, both gas, one from the Ellenburger at about 18,000 feet in North Texas (if I remember correctly) and the other from about 12,000 feet in the outskirts of Port Harcourt in the Niger delta.

However much you have seen pictures or films of such events, nothing, but nothing prepares you for the real thing - the indescribable noise, the shaking ground and the heat from the burning gas plume combine to give a fantastic demonstration of the power which lies in the subsurface. At least the spectacular Rig 20 film must go a long way to demonstrate that power.

Myles Bowen

From Peter Jones (Rec'd 31 December 2011; Pub'd 17 January 2012)

Sir, There are few geologists left who have actually had the unforgettable experience of seeing Rig 20, BP’s award-winning documentary film (Palme d’Or, Venice Film Festival, 1951) showing the fiery blowout of a BP exploratory well at Naft Safid in the Zagros foothills of Persia.

The film showed the huge logistical and technical problems encountered in preparation for extinguishing the blaze with two controlled explosions, one to remove the damaged rig and related debris, the second to snuff out the flame. The operation was organized by Myron Kinley, then the world’s most famous fighter of oilwell fires and blowouts, directing a volunteer crew.

The climax of the fifteen-minute film is the short sequence which, filmed from a rocky hill top nearby, shows the explosion which removed the broken well head Two weeks later the second charge snuffed out the fire, allowing a new wellhead to be installed, shutting off the well. In the words of Henry Longhurst, (1959), author of Adventure in Oil ¹, audiences saw “a demonstration of the forces of nature about which people talk with awe to this day. It is the highlight of a spectacular film made on the spot and is inevitably received by audiences with a momentary silence, followed by a gasp of wonder.  A second or two after the explosion came the fantastic sight of a whole half mile of pipe shooting from the hole.it shot away high into the sky, far above the thousand feet of flame and here, twisting and turning and writhing like a serpent, it broke as into mere piece of string and fell slowly to earth.”

Rig 20 is available in DVD format from BP, but that unforgettable sequence has been cut! Now the DVD shows only an obscured upward view of the base of the smoke cloud filmed from beside the wellhead itself, filmed by an incredibly brave cameraman, with only a brief explanation of what was happening unseen, in the sky above. All that is left now to preserve that event is the still photograph (attached) in Longhurst’s book.

I obtained the CD (gratis, many thanks) from BP with the thought that the film would be a truly unforgettable training tool, showing the geological dynamics and hazards involved in hydrocarbon exploration and development and the role of overpressure in structural geology. However, without that “silence and gasp” reception by audiences, I suspect that the original film would not have received such a prestigious award.

This letter then, is my appeal for support in restoring to the DVD of Rig 20 the content of the original award-winning film, making it a wonderful and dramatic teaching tool for geoscientists as well as many others who work in the oil industry and academia.

Reference

1. Longhurst, Henry, 1959, Adventure in Oil, the Story of British Petroleum. Sidgwick and Jackson, London, 286p.

Watery Mars attacks irons

From Joe McCall (Rec'd 10, Pub'd 15 February 2012)

Sir, After I completed the second on-line note, published in February 2012, a major new article on the subject appeared in Meteoritics and Planetary Science (Fairén and 18 co-authors 46(12), 1832, 2011). This article claims that the existence of six iron meteorites found by Opportunity could be explained by impact into a soft, wet Mars surface, sometime during the Noachian or Hesperian epochs; that they may have been buried, as I have previously suggested (McCall, Geoscientist 15(7), 14, 2005), and later exposed by differential erosion. They exhibit signs of some chemical weathering in the form of cavernous features. During the Amazonian epoch, surface water almost completely disappeared and there was induration of the sediments, differential erosion and deflation.

In my view, the problem in taking back the aqueous erosion of the meteorites (which surely is only incipient) to the Noachian or Hesperian is that it involves taking the fall back many millions - even billions - of years. From my considerable experience of iron meteorites, the reduced iron would decompose rapidly in such an aqueous environment, and the meteorite could not possibly survive in its present state through the Amazonian to be still littering the Martian surface. Indeed this seems to be the conclusion of Schröder et al. (Journal of Geophysical Research 113 PTEO6S22, 2008) who say that reduced iron will oxidise in the presence of water on Mars, even if no additional oxygen I available.

I am not arguing against aqueous conditions on Mars in the early epochs, but I think that to take the time of fall of these irons back to the Hesperian or Noachian is self-defeating, because in no way could the iron meteorites survive the millions or billions of years involved if so exposed so early on.

• Read Joe's first article, Many Old Irons (August 2011)

Earth bloats

Rec'd 17 December 2011; Pub'd 17 January 2012

Sir, I refer to the article in the December/January issue.  This process of Mantle-derived uplift recognised in the North Atlantic Ocean surely has a much more extensive corollary, long recognised, in the Gregory Rift Valley of Kenya. In 1965, I showed that peneplains on Precambrian surfaces on the western margin of the Rift Valley had been uplifted by a distensive process, prior to rifting (McCall 'Geology of the Sekerr Area, Rept. No 65, Geological Survey of Kenya, 859pp). Strangely, Wiliam Pulfrey, the Chief Geologist, would not accept the evidence and added notes to my report to say so, but B H Baker and E P Saggerson recognised the same process, independently, on the other margin. The same distensive process is obviously applicable on a smaller scale to plumes, and also caldera volcanoes, prior to caldera subsidence. The distensive push can only come from the Mantle (?), though whether convection is involved is debatable in these cases: I wonder if it is necessarily involved in the short pulses from the Icelandic plume?