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AUDIENCE COMMENTS
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Paul Everitt - Age of the earth
A very interesting discussion but at the end of the programme, I was left with the impression that all the contributors were really groping in the dark. A comment was made about the geological record being like the works of Shakespeare with only the punctuation left in! If this is the case how can we have any really certainty that the vast time spans postulated are correct. I am a creationist and believe that geology can only be correctly interpreted in relation to a worldwide flood as described in the bible. I was disappointed that no creationist viewpoint was present on the programme.
ageing the earth peter
this programme gave me much food for thought and while I find it fascinating to look at different rock layers in the local landscape and see in them an enormous ancient diary, I'm a bit bothered by the exactitude of dating 'deep time' since I imagine that time itself becomes elastic over such vast spans, and certainly a year as it makes any sense to us in terms of one orbit of our earth around the sun, might have been quite different to what it is now.
Mark Hebda - Ageing the Earth
I was quite excited when I heard the intro to the programme, thinking there would be debate as to the science involved and the assumptions made when using the various dating techniques employed to "date" the earth. Sadly, there wasn't a debate, just the assumption that these techniques are infallible. For example, it is common sense and patently obvious that long-age dating methods should work in situations where we know the age of the rock. Equally, different techniques should consistently agree with one another. However, there are many examples where the dating methods give dates which are wrong for rocks of known age. The K-Ar dating of five historical andesite lava flows from Mt Ngauruhoe in New Zealand. Although one lava flow occurred in 1949, three in 1954, and one in 1975, the "dates" ranged from less than 0.27 to 3.5 Ma! Using hindsight the "dates" are corrected by arguing that "excess" argon from the magma was retained in the rock when it solidified. Apart from implications which I won't discuss, if excess argon can cause exaggerated dates for rocks of known age, then why should we trust the method for rocks of unknown age? Similarly, isochrons make different assumptions about starting conditions. Again data are selected according to what the researcher already believes about the age of the rock. Rubidium-strontium isochron dating technique has dated recent lava flow as being 270Ma older than the basalts beneath the Grand Canyon - an impossibility! Dating methods should also agree if they are objective and reliable. Different techniques when dating the Grand Canyon give different results. By using posterior reasoning, all manner of reasons can be given for the anomalies. Techniques that give results which can be dismissed just because they don't agree with what we already believe cannot be considered objective. Wood found in Tertiary basalt in Australia which could clearly be seen as having been buried in it (from the charring) was dated by 14C (radiocarbon) analysis at about 45,000 years old. The basalt however was dated by the potassium-argon method at 45 million years old! Carbon dating is also highly problematical. A specimen older than 50,000 years old should have too little 14C to measure. Fossil wood found in "Upper Permium" rock that is supposedly 250 Ma old still contained 14C. Accompanying checks showed that the 14C date was not due to contamination. Coal is another example. Coal is supposed to be millions of years old. However, no source of coal been found that completely lacks 14C. The list goes on and on and on. It's a shame that none of these issues were even brought up in the programme.
Harry Morgan: Ageing the Earth
Another very interesting topic. The thing that intrigues me about the effect that cataclysms such as the asteroid/meteor that struch the Gulf of Mexico 65 million years ago and wiped out 95% of Earth's life, is how did regeneration take place since bearing in mind the current evolutionary theory that requires much longer periods for evolution to take place.
R K Cook Geology
Is there another programme which without anachronism, inconsistency or foolishness can conclude a discussion of geology by telling us that next week it will discuss the St Bartholomew's Day massacre? Is the dodo, unlike the chimaera, gryphon and unicorn, the only animal which began in reality and went on to acquire mythic status?
In Our Time
Dear Simon Information about the contributors is on the programme page for Aging the Earth (including publications). Richard Corfield has a particularly comprehensive website and Hazel Rymer has a website at the Open University. Both can be found by doing a google search on their names.
simon ricketts geology
I thoroughly enjoyed this week's programme particularly the digressions. I am an architecture student trying to design a museum of the sixth extinction and find myself fascinated by the debate about the inevitability of a mass extinction brought about by mankind. Interesting this debate should go out on the same day as news about present extinction rates. The dodo digression was therefore most welcome. Geologists find themselves drawn into fascinating arguments which are only understood by geologists, you know the punk rock thing for instance. They are not alone in this, every field has this problem. It is excellent to have a programme which tries to draw these arguments kicking and screaming into the public arena. That it succeeds so well is a triumph. Thanks. By the way, could I perhaps have a transcript, or, failing that information about the contributors? Thank you. It was bonzer. Oh as for Mark Chestnutt's old chestnut, several reptile species survived into today's conciosness, such as the Komodo dragon and the crocodile. David Verrall- surely the ocean was as susceptible to the danger of darkness with a great number of the sea's taxa deriving their energy from photosynthesis? Of all these messages, I most agree with Mike Widdowson. The impetus for all these earth sciences must surely be, in the words of Ehrlich, improving the knowledge of and the chances for biodiversity before it is gone. We are not far off being one of these fossils ourselves, and blowing other folk up doesn't increase our chances.
Ewan McNeill: Age of the earth
I was interested to catch the end of the program today. And would like to point out that some of the views voiced, although widely held as reliable are not definitive. There is some evidence to suggest that radioisotope decay rates do change and that if one considers catastrophic processes as well as processes that we observe today then the earth may be as old as God tells us in his word. The world around us testifies to it's creator and to the way in which we formed it if we will only take the blinkers of geological time scales from our eyes and examine the evidence with an open mind. I would recommend the following book to anyone interested in reading more Radioisotopes and the Age of the Earth Vardiman, Snelling, Chaffin, Baumgardner, ISBN: 0-932766-19-6
Mike Maas, age of rocks
To deduce the age of a fossil from the concentration of a radioactive element you surely need to know the original concentration. How can you know that ? If you assume that a living specimen absorbs the then-ambient concentration of a radioactive element, and that the concentration decays when the speciment dies, you can compare the specimen`s now- concentration with the now-ambient concentration. But how do you know that the ambient concentration has always been the same?
Alan Fowler Ageing The Earth
Why didn't the participants in this programme have the courage to admit that the Cambrian explosion was clearerly an act of creation as evidenced by the fact that the pre-cambrian fossils are entirerly different from the Cambrian fossils, thus ruling out evolution?
Rita Kingham: "Ageing the Earth"
The programme this morning was fascinating, but I should have liked far more detail. The theory of Punctuated Equilibrium, for instance, was not fully explored. I'd have liked to hear more about other mass extinctions (other than the dinosaurs).
Aging the earth - Laura
I was surprised that on the show this morning, different types of fossil record were not distinguished. Evidence in the plant record seems to contradict that of the marine record reviewed today
Philip Gibbard
Dear Melvin Bragg, I have just listened to and enjoyed your In Our Time discussion programme broadcast this morning 20 November on Radio 4 on the theme of geological time. As a professional geologist, and one who has worked with two of your guests (Henry Gee and Richard Corfield) when they were students in Cambridge, I would like to comment on their discussion of time and more importantly the concept of mass extinctions. The concept of geological or 'deep' time is a difficult one to grasp, but which was admirably explained by Richard Corfield; time passes continuously whilst the representation of time in rocks is grossly discontinuous. The problem comes when one wishes to determine the intervals of time represented by an individual stratum or event, such as the Italian clay layer at the Cretaceous - Tertiary boundary around which so much of the discussion on the programme became centred. There is an old concept in geology that the thickness of a stratum (or bed) is no guide to the length of time it represents. The whole foundation of the public debate around the mass-extinction event associated with the extinction of the dinosaurs is that this clay layer represents a very short time, and yet contains vastly higher irridium concentrations than normal for such a thin layer. This observation has led to its association, by an American physicist, with a catastrophic extra-terrestrial source such as the explosion of an asteroid. There is no doubt that asteroids arrive in the earth's atmosphere from time to time, and now and then one of them is sufficiently large enough to cause major perturbations to the earth's climate for a few years following its impact. It is however, a vastly different matter to accept that such an event could be responsible, in all but a very marginal way, for the demise of a group or groups of organisms that had successfully inhabited the earth for 150 million years. To understand how apparently instantaneous events such as mass extinctions arise in the history of the earth requires a more sophisticated concept of the dynamic operation of earth processes than a 'hammer and nail'-like interpretation that attribute apparently catastrophic extinction events to the arrival of extra-terrestrial bodies. Moreover it requires the realisation that a thin bed of clay was once potentially over 1 metre in thickness when it was laid down before being compressed by folding and the weight of the overlying rocks to its present centimetric thickness. The most important concept which is fundamental to any understanding of the operation of natural process on the earth's surface, including the biological processes of evolution and extinction, is that of the threshold. This concept, which has been repeatedly demonstrated by experimentation and observation, holds that natural systems will respond to an external influence by slightly modifying their operation. This slight modification will continue as long as the external influence occurs, but the changes in the system remain reversible throughout. If however, the external influence increases beyond a critical value or strength, the natural system may be forced to change so profoundly that it cannot be reversed. This critical value is termed the threshold. Mass extinctions appear to be merely a very obvious and significant response to the crossing of one of these critical points or thresholds. In the case of the end-Cretaceous dinosaur extinction this critical change was brought about, not by an asteroid, although as your lady geologist pointed out it may have been a contributary final factor, but by events that had been initiated millions of years earlier. These changes where those arising from changes in the distribution of the continents and the oceans on the earth's surface, the most significant of which was beginning of the closure of the mighty east-west orientated Tethys Ocean, of which the Mediterranean is the only present-day remnant. At much the same time, Antarctica arrived at the South Pole.
Mark Chestnutt Age of the earth
Can anyone explain why many cultures have pictures drawn by man of Dinosaur and dragon-like creatures when at that time there should have been at least 50 million years between the two?
Norman Defoe - age of earth
Todays programme did not mention Fred Hoyle and Chandra Wickramasinghe when talking about origins of life and the fossil record. Was there any special reason for this and might the topic be discussed at a later date? I was interested to hear on the programme that the fossil record still has many gaps and I would dearly like to hear a further discussion on up to date ideas about the fossil record to follow today's.
Margaret Ellis - The Botticelli Gorge
The clay layer in the Botticelli Gorge is not the only example of this feature. I'm a guide at White Scar Cave near Ingleton,in the carboniferous limestone of North Yorkshire and there is a 3 to 4 centimetre thick layer of clay between limestone layers there as well. Any information would be gratefully received,...I'm just away to the library to check this out!
Myles Bowen on Aging The Earth
A rather muddled programme which failed to get across to the lay person the basic concept of the sedimentary record. The female speaker in particular seemed to give the impression that different types of rock indicated the passage of time. In my experience the best way to explain to laymen the relationship of rocks to time is look at the present, a period of ,say, one year. In most land areas no sediment is deposited at all; in most of the deep oceans only a minuscule thickness of clay will be deposited, whereas in deltas (eg Mississippi) a meter or more of sand and clay may be deposited. Equally the composition of sediment will vary from place to place; in the deep oceans a thin layer of clay; in areas receiving continental erosion products thicker layers of sand and clay (clastics); in other areas like the Arabian Gulf or the Bahamas calcareous sediments are deposited in varying thicknesses. All this is going on at the same time, so for any defined period in geologic time there may be no sedimentary rock (a time gap), a thin layer of shale ( a condensed sequence) or vastly thicker sequences of limestones or, especially, clastics. All this complicates time corelation. Often the most difficult problem is to spot the gaps in apparently continuous sequences.
Mike Widdowson, Lecturer in Volcanology, Open Univ
I listened with interest to the excellent debate on geological time broadcast today. As ever, the issue was handled and directed well, and although the issues were complex, the ideas remained accessible. I even liked the digression about the Dodo, even though this discursive avenue eventually died a death, so to speak. Perhaps it was a natural dead end during the evolution of the conversation! My main point develops an idea touched upon by Hazel Rymer. Whilst discussing the extinction of the dinosaurs she commented that perhaps the Chicxulub meteorite impact was the ‘straw that broke the dinosaurs back’. In other words the group as a whole were in decline, and the environmental devastation caused as a consequence of the impact, finished them off. I think this would have been a very interesting angle to explore because what was not mentioned in the debate is that many so called ‘mass extinctions’ apparently coincide with periods of immense volcanism – the so-called flood basalt events. The Cretaceous Tertiary boundary, at which the dinosaurs and other biota became extinct, is straddled by the eruption of the Deccan Traps in India. Current estimates suggest that c. 0.5 million km3 were erupted within a 1 million year period, and some individual flow fields are well in excess of 1500 km3, each representing an individual eruptive event. Given that the 1783 eruption of Laki, Iceland was a trifling 15 km3, and caused serious climate deterioration as chronicled by writers (notably Benjamin Franklin) and scientists of the time, together with widespread mortality in western Europe from the choking smogs (or ‘vogs’ as the volcanologists call volcanic fogs), it seems reasonable to assume that each of the Deccan eruptions were far, far worse. Repeat this several tens of times in a relatively short period of geological time to build the Deccan, and surely there is a recipe for environmental disaster. My own ongoing research demonstrates that these eruptions began about 2 million years before the Chicxulub impact, and continued a million or so years afterward. If it is accepted that such eruptions are capable of creating global climate deterioration, then the scene was already set for extinction when the meteorite hit. However, the really curious twist to this story is that dinosaurs, notably the recently discovered Rajasaurus Narmadensis, a type of small, stocky T-Rex, lived alongside the earliest lava eruptions of the Deccan. How can that be if individual Deccan eruptions were so environmentally devastating? The answer must lie in the idea that Earth’s environment can be, to a point, robust and able to withstand the most terrible of blows, be they volcanic or extra-terrestrial. Push that environment beyond its ‘limit’, and the whole complex ecosystem comes crashing down – as seen at the Cretaceous-Tertiary boundary. Surely the challenge now for Earth scientists is to identify what those limits might have been, and then use the discovered information to help inform ourselves how to avoid or mitigate these type of scenarios, be they man-made or otherwise, visiting themselves upon the modern and future world. After all, it would be a pity to see such a bright ape-like creature consigned a few fossils within metre or so of a rock face, and perhaps conveniently preserved below a nice easily dateable volcanic ash, or iridium layer…..
Tom Turner Ageing the Earth
An international geologist by the name of John Mackay recently lectured at an Oxford University debate, his stand on the Genesis account of creation is well docummented. John is among thousands of contemporary scientists who are convinced by the current scientific data of the truth of the biblical account of creation and age of earth dating. Please why not have someone of John Mackay`s viewpoint on your programme instead of today`s trio of evolutionist advocates.
Age of the Earth
Can you explain why many cultures have pictures drawn by man of Dinosaur and dragon like creatures when at that time there should have been at least 50 million years between the two?
Clive Jones - Age of Earth
Can anyone explain the conflicting information about dating using radioactive isotopes on the rocks formed in the Mount St Helens eruption?
Barbara Cordner - ageing of the earth
When it was announced what this week's topic was, I felt a sense of disappointment, and was going to switch off. However, I decided to give the programme and go and was pleasantly surprised at how my attention was held by this topic. I learned and understood terms that i had only heard mention before, the concept of the different rates at which materials deterioate so that ageing can be detected was clearly explained. The speakers were clear and articulate and I understood how once an interest in geology is formed that it could become a lifetime interest. The concept that humans have only been on earth for such a short time, and that should we become extinct there would be very little record in comparison with other lifeforms served to put our little squabbles and wars in real perspective. Perhaps this is why the speakers you had were such a relaxed bunch!!!
David Verrall - Ageing the Earth
I'll subscribe to the asteroid/meteorite cause for "mass extinction" of the dinosaurs, but I have 2 problems. First, if it wasn't a sudden extinction, why do we find fossils of nests with eggs,surely an indicator of normal life being cut short. Second, why did - apparently - marine dinosaurs also disappear, as one could imagine that the oceans would provide a large degree of protection?
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