America is getting further away from Europe. This is not a political statement but a geological fact. Just as the Pacific is getting smaller, the Red Sea bigger, the Himalayas are still going up and one day the Horn of Africa will be a large island. This is the theory of plate tectonics, a revolutionary idea in 20th century geology that saw the continents of Earth to be dancing to the music of deep time. A dance of incredible slowness, yet powerful enough to throw up the mountains and pour away the oceans.
Plate tectonics was a genuine scientific revolution. It made geologists and many more besides profoundly re-think what the Earth was, how it worked and how it related to all the things in it.
Contributors
Richard Corfield, Visiting Senior Lecturer in Earth Sciences at the Open University
Joe Cann, Senior Fellow in the School of Earth and Environment at the University of Leeds
Lynne Frostick, Director of the Hull Environment Research Institute and Professor of Physical Geography at the University of Hull
Audience reactions to this edition
Plate tectonics
From what I can gather in regard to what I have heard of GPS data, a) subduction is occurring at ocean trenches and b) the earth is *slowly* expanding.
Penelope Cooper Plate tectonics
In the interest of open mindedness I've just taken David Edwards' advice and checked out the Expanding Earth video on youtube. Very interesting. Having studied plate tectonics and geology as part of my degree I can remember all the evidence presented in support of the theory, and have seen the mid-Atlantic ridge in Iceland personally. The video rather skims over how the subduction zones, lava production and volcano formation work in this process. How does it account for the undoubted existence of the mid-Atantic ridge and the presence of Iceland? Is there anywhere that this expanding earth theory is more deeply (and scientifically) explained and substantiated?
Magnetic Pole Reversal - possible topic?
Hi,thanks for another fascinating programme on Plate Tectonics.Listening to the brief comments about the reversal of the magnetic poles made me think that a programme dedicated to just that topic would be very interesting: what we know about the poles now; how we know they have swapped in the past; when they are likely to again; and the impact that would have. Probably enough for more than just one programme!Keep up the good work.RegardsAndy Hewson
Chris Matkin/Plate Tectonics
A stimulating programme which added to my geological knowledge of the subject gained some ten years ago in a Faraday lecture. The latter explained various points not touched on by your panelists1] a surprise was that a multicoluored geosphere demonstrated to the audience showing the positions of the plates was unrecognisable vis-a-vis the prsent topograhy of the continents2] Subduction: why isn't the crust dragged down as well as the granite/basalt plate on which it is riding?3] How does lubricating seawater penetrate the said plates which, as igneous rocks, would be presumed impernable?4] No reference was made as to the temperature of the black smokers but the following anecdote was related in the Faraday lecture. Geologists, by their natures, are adventurous and in a first survey, at extreme depth,the man in charge manouvered his submersible to within a few feet of a column. He then edged closer and stuck the poboscis of the module's probe into the smoker; it melted and disappeared in an instant. He radioed up to a techie on board, what's the melting point of the probe? Answer, 800c...exit, pursued by a bear! With temperatures in excess of 1000c, why doesn't the ocean boil despite the depth and pressure?
Dave Plate tectonics
Fascinating programme. It was argued b y the panel that plate tectonics was only accepted in the 1960’s and those putting it forward were almost shown the torture instruments as per Galileo. Only puzzle for me I was at school in the early 1950’s and I am sure that it was put forward as a theory or hypothesis in the back of my school atlas.That would have been around 1955. But probably just as a hypothesis.Still want a plug for a programme on Science Fiction and Fantasy with my favourite author Terry Pratchet with Jack Cohen and Ian Stewart.( Science of Discworld)Sci fi an Area where all sorts of things were discussed which religious thought did not allow? For example responsibility of Frankenstein to his monster that of God to man? Difficult to put in a category though.
David Edwards and Plate Tectonics
What we've just heard from these most distinguished guests about Plate Tectonics is utter hogwash. Their so-called model requires that continents glide around upon deeper levels of the planet is absolutely impossible. To try to make it seem possible they invoke a mechanism in which plates actually dive below each other; and this is even more impossible! The truth is that the world has expanded over geological time. This created the vast oceans, whilst the continents themselves remained fixed (rock solid). A superb short three-minute video of this process may seen by searching youtube: Expanding Earth Video, or Neal Adams. Please judge for yourself once you have watched this, it requires no convoluted disingenuous arguments, only simple logic.
Chris Butt - Plate Tectonics
Excellent programme.Presumably the sub-sea volcanic activity produces enough CO2 to influence the atmospheric CO2 readings and "man made global warming" ?
Dr Simon Allen, Univ of Edinburgh - Plate Tectonic
Although your speakers provided an excellent introduction to plate tectonics, their presentation of Lovelock's Gaia theory was somewhat 'adrift'. They failed to mention the essential idea: that the favourable conditions for life on Earth (such as global temperature suitable for life, 20% oxygen in the atmosphere) are maintained by the activity of the Earth's organisms. Lovelock's main claim is for this role of 'life' in planetary regulation, as an *unconscious* and automatic process that arises from tight coupling between the evolution of life and the Earth's physical environment through geological time. This is in not in any conflict with the idea of plate tectonics, but neither is it superseded by plate tectonics as some kind of superior theory. They are two different ideas, explaining two different sets of phenomena, and are not mutually exclusive. Lovelock himself keenly supports plate tectonics, and often offers it as an example of the kind of paradigm shift in science represented by his own Gaia theory - which was also unacceptable to mainstream science until a causal mechanism was identified (in Gaia's case the Daisyworld thought experiment). How about focusing an edition of In Our Time on Gaia theory? It is generally poorly understood, but highly relevant to current debates about the sustainability of human society.
Ken Goddard, Plate Tectonics
In 1967 I was working the 'sandwich' part of my four-year civ eng degree and renting a bedsit in a large, rambling and run-down old rooming house in the village of Sutton Valence in Kent owned by a rather run-down chap of about 60, a retired geologist.He was absolutely adamant that he had been the first to come up with the idea of plate tectonics but that others had stolen the limelight from him. He seemed so genuine about the issue but also consumed by it unfortunately.If he did have a genuine case he wouldn't be the first in science would he?
Donald Bayley : Plate Tectonics
The discussion around black smokers and the molten magma beneath the earth's surface failed to throw any light on the source of the heat required to keep this vast mass in it's present state !
Anne Studd - Plate Tectonics
A great programme and very enlightening about the reluctance of so many to grasp new ideas.I studied A-Level Geography from Sept 1960 - June 1062, also Geology. During that time we learned about Wegener's theory, Gondwanaland, Pangea, etc. all as quite separate entities. The whole area of plate tectonics and continental drift fascinated me and, when I was asked to elaborate on the theories in my final exams, I was already convinced that all these ideas were so obviously part of the whole answer and no one was right to the exclusion of the rest as I had been taught. I made my argument, and was surprised to find that I received a much higher grade than predicted, so my thinking must have reaonated with the examiner. I was amazed today to hear how far ahead British schools were, at the time, compared with American universities in this field.
Paul Davies - Plate Tectonics
a great programme, but some curious omissions.No mention of the influence of plate tectonics on mass extinctions, especially the end-Permian event. The Gaia theory mentioned essentially says organisms arrange the Earth's conditions to suit life; mass extinctions would tend to disprove this.
Maddox - Plate Tectonics
The renaming of Alfred Wegener's Theory of Continental Drift as Plate Tectonics served only to obscure its earlier origins. Wegener was of course incorrect in the mechanism he proposed for the drift. However the denial of the evidence of Continental Drift by Geologists for thirty years was clearly embarrassing and its re-naming and re-packaging as the new discovery of Plate Tectonics a more palatable necessity.
michael kimmins plate tectonics
No mention was made, as far as I am aware, of convection cells rotating between upper mantle and core, hot rock rising from above the core and the cooler in the upper mantle sinking, to provide horizontal movement of surface plates. Is this theory now discarded?
Plate tectonics
Just as the Steady State theory of the cosmos was, in the 20th Century, discredited in favour of an expanding universe theory, yet now is commanding a renewed interest, so - somewhat conversely - the Expanding Earth hypothesis that was similarly discredited in the 20th Century is commanding renewed interest. But not, of course, in the mainstream academic journals.Probably like many visually minded people, my grandmother, herself not a geologist, long held that the continents were once a single land mass, a view based on the apparently scientifically inadmissible, yet manifestly remarkable evidence of the shape of their coastline. Were it not that academe has shown itself time and again to be steeped in dogmatism, it would surprise me that it wasn't until as recently as the 1970s that plate tectonics became accepted mainstream.
Jon Hurwitz - Plate Tectonics
Richard Corfield's comment that animals and plants are not colonies of microbes because mitochondria and chloroplasts may originally have been bacteria but have long since fused into something new, misses a point. The average human consists of ten trillion human cells and a hundred trillion microbial cells, colonising our alimentary canal and mucosa. So I think calling Joe Cann's description "patently absurd" was a little overstated.
Roger Wood - plate tectonics
Great programme, as ever - I always appreciate the way the you succeed in bringing out the excitement of discovery via the historical development of the topic, this time by people who were actually there! Two, for me, significant omissions though: no mention of the actual rate of present day continental drift (usefully expressed in millimeters per year - about the same rate as your fingernails grow); or the fact of direct verification by modern measuring techniques, particularly satellite laser ranging (SLR). By repeated measurement of the return flight times of short laser pulses to satellites equipped with special reflectors, data from the global network of 40 or so SLR stations allows analysts to compute precise orbits for these satellites. These orbits may then be used as references to monitor the relative motions of individual observing stations on the surface of the Earth. The measurement precision is now such that even small annual drifts can be confidently determined in just a few years. Perhaps the whole topic of today's geodetic measuring techniques (SLR, GPS, VLBI, DORIS) might be one for a future programme?
David Thompson - Tectonic Plates and Evolution of
I agree with tectonic plate theory and with the theory of evolution. I was surprised though that no mention of the movement of the earth round the sun or interstellar movement was mentioned. Surely just as the earth, as a planet, moves, the whole cosmos is moving and some degree of movement must be communicated to/be inherent in this planet. Also when,towards the end of the programme discussion moved to the origins of life (cells v. microbes, etc) no mention was made of either the role that switching polarity might have in creating elecrical impulses( as though the earth is a great dynamo) and no mention was made of the on /off effect of day and night. This on/off effect and changes of polarity are not optional extras - they are part of the whole and I think their part, like planetary movement, needs to be recognised. Thanks, I enjoyed the programme and these comments are intended constructively.
Ronnie Brown, Plate Tectonics
It is surprising that Alfred Wallace is not mentioned in conjunction with continental drift and plate tectonics. The `Wallace Line' and its existence because of movement of Australasia was accepted long before Wegener was howled done for suggesting continental drift. I also remember an old biologist telling me of the ways his lecturers `explained' similarities of flora and fauna on opposite sides of the Atlantic. Why was the connection with the Wallace Line not made? Fred Hoyle in his autobiography also asks why Wegener has not had notable honours from the geological community. All this is interesting from the viewpoint of changing paradigms in science. My professional interest is to see similar phenomena in mathematics. www.bangor.ac.uk/r.brown
Anni - Plate Techtonics
Wonderful program. You have confirmed me as having a predominantly scientific brain (I loose you in the philosophy progs)and allowed me to continue to espouse Lovelocks theory. please thank your contributor who NEEDED to go out for a good cough, but stayed to the end...
margaret keirnen - plate tectonics
Thank you so much for your plate tectonics programme - it brought back good memories. I was taking my Geology Finals at Manchester University in 1965 and one of the questions was to argue between 3 theories - one of which was plate tectonics. (luckily I favoured plate tectonics!) Margaret Keirnen
Dr Ben Ross
'Magnetic north and south swap regularly.'Why?
