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This is about science produced by the California Institute of Technology and originally broadcast my station KPCC in Pasadena California. The programs are made available to the station by national educational radio. This program is about continental drift with host Dr. Peter less a man and his guest Dr. Arthur Bucco professor of geology. Here now is Dr. lissom trawls look Vick dogs and off Oxford mathematician of the placid Victorian era gave much to the world not through his researches in mathematics which were serious and sound of somewhat uninspired. But through his incidental activity for which he is far better known using the nom de plume of Lewis Carroll he wrote the two famous books Alice in Wonderland and Alice Through the Looking Glass and what a wealth of pleasure and wisdom in those great books have given through the ages to children of all ages. In one of the Alice books a character probably the White Rabbit who would have been described
today as insufferably square remarks that he has not enough time back replies his sage companion. You have all the time there is. And that is that is our one gift in this fast moving world. We all of us have all the time there is but time means different things to different man. To the scientist in particular. Time is infinitely expandable a contract a book. To some scientists physicists for example. The second is an infinite age. To others a million years is but a moment ago many millions of years ago when the earth was young and violent long before man or dinosaur had trod the continents and the oceans appeared and took shape but what shape did Africa exist. And where was America and how has the map of the world changed over the
eons and how have the continents drifted or have they after all. I guess today is a man to whom a million years is a mere bagatelle. Dr. Arthur book is spent his research in the persecutor of the subject of the continental drift. He did his undergraduate work at Harvard and took his Ph.D. there as well in geology and Penny ontology. He worked for a while with the US Geological Survey toward MIT and is currently professor of paleontology at the California Institute of Technology and his subject is the eternally fascinating and controversial one. The Continental Drift author. What exactly is the that the basic thrust behind the idea of the continental drift and how is your work related to that. Well Peter basically the question is a very simple one
simple inspection of the globe leads one to the impression that there's a real possibility for continental drift to ever have occurred. For example if you examine the shoreline of Africa or in the south america opposite to it you will note that there is a fairly close fit of the shorelines. This was noted very early by then in the time of Sir Francis Bacon. As soon as the early charge brought back from the exploring expeditions arrived in the seventeenth century Bacon himself suggested the possibility for continental drift. Since then additional evidence of a more sophisticated nature has accumulated particularly that contributed in the last hundred years or so by the geologists studying the rocks on the continents and by the paleontologists studying the animals and plants contained in these rocks.
Of course author this is not to suggest that this drift or movement of the continents took place in any historical time at all we are talking many many millions of years ago. Yes if Continental Drift occurred it presumably took place at some time many millions or hundreds of millions of years from the present moment. There is indeed great controversy among the advocates of continental drift as to the precise time or times when Continental Drift took place. The exact mechanism as well is in some dispute. Now the evidence that I would like to discuss with you is basically of two types. I am studying the patterns of distribution of different types of sedimentary rocks on the continents. For example the distribution of limestone was formed on the continents and shallow seas of the past. The distribution of mud stone silt stone
on the same continents and concurrently the distribution patterns of shallow water marine organisms on the continents. So I thought you are studying these shallow water marine organisms but why do you study them why do you study animals at all and and if you're going to study them why should you choose something as what seems to us as dull as a clam or an oyster. Well the time interval I'm interested in pater happens to be the Syler Ian and Devonian interval. Oh I must stop you that I've always wanted somebody. What where did those names come from and what do they refer to. Well the term Siler Ian is a British derivation as is Devonian the side lowers where a tribe of Celts living in Wales extinct many years now and their name was selected as a suitable acronym for a group of rocks studied many years after their extinction by Sir Roderick Murchison.
The first director of the Geological Survey the Devonian was named after Devon in the south of England where rocks of Devonian age were first differentiated from older and younger rocks so the Devonian really describes the place where these very aged rocks were first positively identified. Correct. Well no talking we know roughly what we were talking about by the way you didn't say just about how many million years ago that is. There's areas where our well paid are in absolute terms the Syler E and the Devonian periods would occupy a time interval between a let's say in round numbers three hundred fifty to possibly 400 million years ago. It's difficult to be precise about the absolute time involved because this involves radiometric measurements obtained from minerals which crystallized an igneous rocks or formed by precipitation in the sea during these celery and the Devonian. And
unfortunately these minerals and the radio active daughter products formed from decay of radioactive isotopes incorporate in certain minerals have often undergone very complex histories. They literally have not been formed in a bottle which is then been kept and placed on the shelf and then allowed to wait undisturbed for three or 400 million years and then analyzed. They've undergone subsequent heating squeezing weathering passage of solutions and these processes have tended to remove daughter products or possibly add parent products and to one might say it complicates the history of these built in clocks considerably. And Sir Arthur we are talking as you point out about this Hilarion Devonian age is 300 million years ago. Well we all know that a one week old oyster is a pretty odious thing. But I guess we're going to have to talk about
300 million year old clams. So let's go on about these sort of animals particularly these these shallow water molluscs that lived in that area and what you learn from them. Well the Bible as I study are technically known as the bracket pods. They are a group of by a house resembling the modern scalloped in some respects although one might use strict point of view a considerably different. They're restricted by and large relatively shallow marine waters. I'm quite interested in learning as much as possible about their evolution and their distribution in particular their animal geography you know possibly I should take a moment out and define for you just what I mean by the term animal geography. Most of us are familiar with the fact that on the land we get different groups of mammals in different continents for example the herbivores and carnivores of Africa
are rather different than those of South America. And in turn both of these continents have a very different my million fauna than is currently found in Australia. And it appears that isolation has been a very important factor leading up to these currently extremely different faunas in the shallow marine waters isolating mechanisms are equally effective in producing distinctive groups of shallow water animals. In other words they all live in their own little watery watery valleys and have no communication and contact with their neighbors. That's essentially it Peter. They're effectively prevented from interbreeding and exchanging their genes if you will. And that's having a widely distributed pattern as a result. This type of restriction is seen at all levels amongst plants and animals even amongst ourselves we're familiar with the fact that in conditions of isolation with relatively small populations we tend to get some very interesting types to develop.
For example the Eskimos living under very difficult conditions in the Arctic become a relatively inbred and very homogeneous group. The same would certainly be true of the Australian aborigines until the advent of Western man interfered with the normal situation. And so you were able to find out if you can find the fossils of these these aged. Climbs in different places that you then assume that they all came from some original place and you get a feeling about where the continents have in fact shifted. Well my basic problem with the animals. The shallow water animals that I devote my time to is first of all trying to differentiate the effects of local differences in environment which will of course induce quite different species to settle on different types of bottom and those effects due to isolation cutting off one region of the sea from easy communication with
another. For example in relatively shallow waters you may expect oyster banks muscle banks clam beds and so forth. And depending on the suitability the bottom of the temperature of the water or ph or other factors unspecified of a biological or physical nature. You can get a host of little micro environments each with its own distinctive group of clams or in my case bracket pods. And now what do you actually learn from these different groups of bracket pods. Well what I am striving to find out is something about the boundaries between various provinces. Areas which were isolated from each other from an interbreeding point of view in the Silurian and the Devonian and presumably by learning something of this type. We can get some clues as to the distribution of the Marine currents which were capable of carrying larvae about from one region of the earth's surface to another.
Now as far as Continental Drift questions go this is a bit vexing because the Marine currents can act in a variety of ways and be influenced by a variety of physical phenomena so that using the evidence obtained from animal geography to try and solve some of our questions of continental drift is a bit tricky because we have to be continually on the alert not to fall into the trap of concluding that because two groups of animals on two separate continents are similar that they at one time lived very close to each other. They undoubtedly if they are truly similar shared some type of common ancestry and may indeed have been part of an essentially interbreeding population. But to jump from this conclusion to the conclusion that they lived close to each other geographically is at this stage of our knowledge rather uncalled for.
I see so that really is how you study the animals and what you learn from them. Now what about the other aspect of your studies authored the study of minerals. How do you study them and what do you learn from them. Well inescapably in connection with my work on the bracket guides I have to deal with the sedimentary rocks which in tomb the shells the sedimentary rocks are made up of a variety of minerals chiefly degradation products of older rocks sedimentary metamorphic and igneous and also biogenic in Arjun biogenic being just a fancy word for the Calla carry of skeletons chiefly of marine organisms. In other words these are graveyards of all these aged climes we've been talking about exactly. Now in some areas of the continents we have a rather stable situation in the vertical sense where the continents don't go up very much or down very much. In these stable areas when they're covered flooded with seas
we have great accumulations of shell debris which when litho fied we would term limestone or even slightly altered subsequently by interchange with seawater dolomite little bit of magnesium going into the calcite structure calcium carbonate and replacing it. So when we find a vast area hundreds of thousands of square miles of continent underlaying by limestone of a particular age we conclude that this area was relatively stable for a rather lengthy time interval. If the area in question was slightly above sea level we of course would expect to find non marine deposits or possibly areas subject to Danube Daish and erosion. And this too can occur for example in the central part of North America the so-called Canadian Shield as oscillated around sea level for a very long time. At present most of it is above sea level a little bit seldom more than a few hundreds of feet
and the sedimentary cover being laid down is chiefly of non-marine character peat bogs river silt things of this type. Now in strong contrast to these relatively stable Continental environments both marine and non-marine we have what we might call for lack of a better term unstable environments unstable in a vertical sense these unstable areas are characterized by a very irregular distribution of sedimentary rocks from the point of view of their mineralogy and their thickness. Now that I would have thought made it difficult for you to put the puzzle together all. Well yes and no. If Ford has problems but also possibilities because basically what we would like to do with this problem of distribution of rocks representing a stable environment and rocks representing an unstable environment and I might add again that these two suites or rocks are easily distinguished from each other on the basis of
a greater thickness of the unstable suite as opposed to the stable one and also the somewhat different bulk mineralogy of the two carbonate rocks for example are very uncommon in the unstable environment. We can't take the boundaries on the various continents between the stable and the unstable sweeps of rocks. Carry these boundaries out to the margins of the present continents and then project them to adjacent land masses and try to get some idea as to whether the fit is reasonable. Essentially treat the thing as a jigsaw puzzle. Look at the stable areas on both sides has one color if you will the unstable areas as another color. See if the dimensions of the fit are right. It's essentially just a problem of putting a jigsaw puzzle together. Now admittedly if Continental Drift took place it's quite fair to assume that a few bits may have been lost or mixed up near the joins and it's also quite fair
to assume there may have been little distortion here and there. Rocks do get folded occasionally broken so we mustn't expect a perfect fit to the nearest thousandth of a millimeter or anything of that type. But still as you say by taking the animals and by checking the mineral deposits we can see if different parts of the COB the continents fit or API to fit together and get some idea there about the great problem of continental drift. What actually do we know at the present is there anything we can say for sure. We're using the data I've accumulated paper on the side Larry and the Devonian. There are some observations which I've made which lead to the following conclusions. Now I should insist of course that these conclusions are tentative as any conclusion in science must be but based on our knowledge of the distribution of sedimentary rocks reflecting both stable and unstable environments I think it's safe to say that
Africa Europe and Asia have formed essentially one block since the beginning of the Cambrian period say half a billion years. In other words it Africa Europe and Asia occupy the same positions relative to each other though not necessarily to the other major land masses as they do at the present time. So they're stuck together and they always have been what about the Mediterranean Sea they're often well in middle of the Mediterranean Sea it first appears to be that of a stumbling block here. However the Mediterranean Sea. From my point of view is merely a Red Sea and I might add here apparent that actually that the Red Sea is a very lately formed crack if you will in the earth's crust dividing off Arabia from adjacent parts of Africa. Now I believe when I say lately I mean something the order of 25 to 30 million years. But still. Now possibly this is cowardly on my part after I've had an
opportunity about 20 years now to summarize the available data to inspect it carefully. Turn on the bracket ponchos over at least once twice thrice. One might hope I would arrive at a conclusion but I feel that scientifically this would be on the sound and I prefer to defer a conclusion at this time and to state quite simply that my data is consistent with either view. Well I thought you would talk about twenty Yeahs on being when one might be able to say things with a little bit more reliability. What do you see as the future prospects in the study of the continental drift. Well I think using the methods which I have employed Peter and I might emphasize here the chief virtue of these methods is the application of great diligence in the study of available information both from a library point of view and from a museum collection point of view and also from the point of view of going out and making my own collections and studying them on a worldwide basis.
But the application of this type of diligence if you will permit me on a worldwide basis to the whole column geological column from the Cambrian to the present is a possibility as yet largely untried. Now I've gone ahead for this I Larry and the Devonian and prosecuted my own interests. However considering that the beginning of the Cambrian is between five and six hundred million years ago in my own time interval Siler in a Devonian and compasses possibly 40 50 million years and who's already on the tree. You follow you can see that my sample is a relatively short one and because of the sampling difficulties it's not surprising that I can't arrive at all the conclusions one might hope for. Author You speak very much about diligence in the research. Is there any way in which what we commonly refer to today as the new space age tools is there any way in which modern advances in other fields have greatly accelerated your work.
Well I'm afraid that the only really modern tool which is accelerated in my work is the current greater availability of funds for travel to distant places to collect fossils. Some of my colleagues this is a matter of humor to my wife it's a matter of some concern on occasion when trying to raise four small children. However it's an essential element in developing a grasp of just what really goes on on a worldwide basis. Photographs and descriptions of shells found in Malay are near the South Pole or in Siberia are fine and they do convey an impression but to really understand these things firmly one has to see with his own eyes. Unfortunately Billy intelligibly as in many fields of human endeavor seeing is believing. Now admittedly sometimes one can be misled but by and large I feel. Much happier when I can see the evidence
firsthand. So you know space age tool is in effect the airplane in the passport. Essentially what about some of these things that we think about. Radiometric Gage has some way of atomic aging or computers too to collect all this this vast mound of information that you can't offer. One of our key problems undoubtedly in geology as in other sciences is a question of how to handle tremendous accumulations of data in an intelligent and economical fashion. Unfortunately in my own field the most important thing to do is not to process all the available data in one critical fashion but to analyze what's available in a very critical manner. So I would say that the most important thing that the paleontologist can contribute to this question of continental drift is to approach it from the point of view of critical assessment of all the available data both physical and
biological on a worldwide basis. Now again this calls for great patience and diligence. But after all this in many ways is the essence of the search for knowledge in any field. And so we see that they great study of the continental drift. Pursues its course by studying the animals of the ocean by studying the minerals and seeing whether they match. We are making slow progress and putting together that great Humpty-Dumpty of what our continents are today to what they might have been 300 million years ago. And as who really with all things the tools of the trade are not particularly fancy or elaborate but just plain diligence hard work intelligence and original ideas. Thank you Arthur. This one is about science with host Dr Peter listen and his guest Dr. Arthur Bucco join us again for our next program on Dr. Robert McGregor Leanne will lead a
discussion about arms control about science is produced by the California Institute of Technology and is originally broadcast by station KPCC in Pasadena California. The programs are made available to the station by national educational radio. This is the national educational radio network.
About science
About continental drift
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California Institute of Technology
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University of Maryland (College Park, Maryland)
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Episode Description
This program focuses on the scientific study of continental drift. The guest for this program is Dr. Arthur Boucot.
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Interview series on variety of science-related subjects, produced by the California Institute of Technology. Features three Cal Tech faculty members: Dr. Peter Lissaman, Dr. Albert R. Hibbs, and Dr. Robert Meghreblian.
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Guest: Boucot, A. J. (Arthur James), 1924-
Host: Hibbs, Albert R.
Producing Organization: California Institute of Technology
Producing Organization: KPPC
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University of Maryland
Identifier: 66-40-50 (National Association of Educational Broadcasters)
Format: 1/4 inch audio tape
Duration: 00:28:06
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Chicago: “About science; About continental drift,” 1967-08-22, University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC, accessed June 20, 2024,
MLA: “About science; About continental drift.” 1967-08-22. University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Web. June 20, 2024. <>.
APA: About science; About continental drift. Boston, MA: University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Retrieved from