FULL EPISODE Lesson 09 Continental Drift – Understanding the Earth

many of the islands of Arctic Canada are formed of limestone deposited in a warm subtropical Sea about four hundred years ago and if one goes to the opposite all there to find coal scenes not deposited under tropical conditions but certainly under very much warmer conditions than Antarctica has at the present time now you know from your knowledge of plate tectonics how those seeming anomalies can be explained the continents have moved they’ve moved as passengers on the rafts which are the plates of the surface shell of the earth but the idea that the continents had moved was one which was very difficult for scientists to accept and the difficulties that they had were often associated with the lack of enough evidence to support the theory it isn’t any good just having one piece of evidence to support a theory you must have evidence from many quarters and it must all be convincing for example the equivalent of earthquakes on the moon that we call moon quakes travel with a velocity through the moon of about just over 1.2 to 1.7 nearly 2 kilometers per second through that rock a piece of cheddar cheese would transmit those moon quakes it just the same velocity about one and a half kilometers per second so from that observation that single observation it would be possible to conclude that the moon was made of cheddar cheese and of course we know it isn’t it’s ludicrous but it is supported by that one piece of scientific evidence so when you look at the following hour and particularly at the first half hour which is the planet of man program beyond a doubt revolution remember that you’re looking with hindsight and that the scientists of that time was simply exercising the skepticism which keeps science progressing it’s just been a real revolution in the earth sciences it follows a traditional pattern that has occurred in other sciences in this case the the great concept has been that the continents can move about and are not fixed and the experience in the other sciences has been that when such a change in ideas occurs immediately after that there’s a great opportunity for advance many lesser things become clear and so we feel that will be a very great advance in the earth sciences during the next few decades the minuet is a stately dance for nobility encumbered by their extravagant costumes the couple moves in a stilted fashion elegance gives way to walk wordless until the dancers are entirely out of step with the times revolutions are violent upheavals that rupture ties with tradition members of the establishment invariably muster to counteract such canons of change but are eventually destroyed when the force of popular opinion sides with the revolutionaries the revolutionaries bring about a major shift in the way man perceives himself you slogans emerge old dogmas tumblr the king is dead long live the revolution yep who is to check the power of the citizen who believes in long laws and short lives the epoch of man is a chronicle of revolutionaries who stood by to provide new solutions the history of science is also the drama of revolutions passionately fought by radicals who defied Authority to expand knowledge who turned their world upside down

the creative scientists deals with problems of cosmic proportions the conversion of the mind of man but man does not readily grasp new notions he fixes on old concepts basic images and simple forms the heavenly bodies hint of the divine form circularity even the window to the soul is so shaped the sir it has no beginning no end it embraces perfection it’s regularity is comforting in the 5th century before Christ Plato propounded the notion of perfect form and bound scientific inquiry in a straitjacket for 2,000 years those lovely patterns in the heavens are decorations in the visible world but they fall short of those which are true the true forms I tell you can be apprehended by reason and thought but not by sight the shoe problems in astronomy as we do in geometry and leave the starry heavens alone by reasoning before the fact the individual arrives at truth the world is corrupt change is an illusion all true motion must be uniform in circular 500 years later Ptolemy looking at the night sky is spellbound more by Plato than by what he himself observes we believe that the object which the astronomer must strive to achieve is this to demonstrate that all the phenomena in the sky are produced by uniform and circular motions yet he had observed that the motion of some of the planets unlike the stars was zig-zag at times Mars stands still in the sky reverses direction and then pursues its former course but the arbitrary law of uniform motion and perfect circle’s must be preserved Ptolemy begins his model of the universe with a series of Earth centered planetary circles on the circumference of the large circles he places smaller rotating circles and behold the divine ferris wheel a combination of perfect circles that will keep man entranced for another 1,500 years by the end of the 15th century the Ptolemaic model began to creak but not with the rest of observable fact Copernicus was even more enchanted with uniform circular motion than Ptolemy the Ptolemaic system while saving circular motion did not quite maintain uniform speed having become aware of the defects I often considered whether there could perhaps be found a more reasonable arrangement of circles in which everything would move uniformly about its proper center as the rule of absolute motion requires in the sixteenth century a revolutionary was born who before he dismantled the models of Ptolemy and Copernicus would state Oh for supply of Tears that I may weep over the pathetic diligence of one who relying on Ptolemy wasted his valuable time and ingenuity in the construction of spirals and loops in order to represent that which exists only in the mind the times are ripe for Johann Kepler precise data on planetary motion is being collected and the Copernican model does not accurately predict the position of the planets after a false start in trying to unlock the secret of the orbit of Mars Kepler discovers that his model is inexact by a small time margin if I had believed that one could ignore these minutes I would have patched up my hypothesis following six years of struggle with mathematical computations he discovers that the orbit of Mars is elliptic the key to planetary motion was a cosmic egg not a perfect circle because Kepler chose to abandon conventional thought and stuck with

stubborn facts he broke a 2000 year trance but if the earth moves about the Sun as Kepler had now proven and is not the center of the universe mankind yearned for a new form of stability he turned from gazing at the Stars to gaping at the ground itself for the security that some part of his universe was steady and unchanging even today our cliches betray this common sense feeling keep both feet firmly on the ground until the early 20th century fuel physicists asserted that the oceans and continents were permanent features on the surface of the earth they conceded that the land rose and fell but always in a series of uniform cycles the earth was a steady-state machine ever maintaining a harmonic balance between sea and land this doctrine known as uniformitarianism had the ring of Plato as long as geologists chiseled at hard rock and studied the minut features of the earth the impression of a solid earth would remain imprinted in their minds but now what profound notion was this you need man entertaining it may have been this rifting and shearing that led him to shatter the established view of a rigid earth as kepler before him as a student of meteorology in berlin Alfred Wegener had devoted long hours to physical conditioning in preparation for his expeditions to Greenland little did he realize then that he would have to draw upon this reserve of strength to endure the rage of the scientific establishment which he would soon provoke in 1915 he published a radical book in which he contended that the continents were drifting like pieces of a cracked ice floe the concept of continental drift first came to me as far back as 1910 when considering the map of the world under the direct impression produced by the coastlines on either side of the Atlantic at first I I did not pay attention to the idea because I regarded it as impossible according to Associates he had mentioned the idea much earlier in modesty he attributes the illumination to accident but fortune favors the prepared mind in the fall of 1900 and 11 night came quite accidentally upon the synoptic report in which I learned for the first time of paleontological evidence for a former land bridge between Brazil and Africa as a result I undertook a cursory examination of relevant research in the field of geology and paleontology and this provided immediately such ready corroboration that a conviction of the fundamental soundness of the idea took root in my mind it is just as if we were to refit the torn pieces of a newspaper by matching their edges and then check whether the lines of print runs smoothly across if they do there is nothing left but to conclude that the pieces where in fact joined in this way let us assume that we can bet ten to one of the correctness of turf theory just on the first line alone the folding of the Sierras of boy desirous and the cape mountains then since there are at least six independent tests available we can bet a million-to-one on the theory being right about 200 million years ago he concludes a supercontinent Pangaea began to break up and continental pieces drifted to their present positions we may assume one thing as certain the forces which displace continents are the same as

those which produce grateful mountain ranges continental drifts faults earthquakes volcanoes polar wanderings are undoubtedly connected causally on a grand scale however what is cause what effect only the future will unveil a year after the 1922 edition of his book is published the Royal Geographical Society meet to consider vague iners hypothesis the high priests of science convene to suppress heresy in examining ideas so novel as there’s a Vigna a moving continent is estranged to us as a moving earth was to our ancestors and we may be as prejudiced as they were it is not easy to avoid bias whatever his own attitude may have been originally in his book he is not seeking the truth daga Nara has come forward with the theory which deals with the distribution of the continents in a bold way and offers himself for sacrifice he is certainly getting it three years later the American Association of petroleum a symposium on the drift theory at which vagin or himself is president we are to believe Wagner’s hypothesis we must forget everything which has been learned in the last seventy years and start all over again my principal objection to Wagner’s hypothesis rests on the author’s method this in my opinion is not scientific but is a selective search through the literature for collaborative evidence and and in a state of auto intoxication we are on safe ground only so long as we follow the teachings of the law of uniformity the battle over the theory of the permanency of the Earth’s greater features has been fought and won by Americans long ago fifteen years later a battle erupted which was the field of Admirals and Generals not geologists and geophysicists engaging in anti-submarine and minesweeping operations British and American scientists felt a tedium after their initial success in deploying their weapons of destruction after the Battle of the Atlantic scientists turned to modifying the electronics of war into instruments of research others acquired another skill before the war science was considered a hobby by those outside the profession because of their contribution to the war effort scientists acquired a new prestige they learned how to lobby for money with an intensity to match their newly acquired esteem only when scientists turned their backs on the comforts of libraries and boarded ships with advanced funding and tools with the oceans unlocked the secret of the continents during the 50s geophysicists conducted extensive ocean bottom profiling if the oceans were permanent features the sediment accumulated from continental erosion over four billion years should be about four miles thick the echo sounding profiles beyond the continental slopes reflected an average thickness of only several hundred feet there was yet another surprise expecting to dredge up ancient Precambrian rocks the drill cores consistently sampled Rock less than 200 million years old the ocean basins were youthful less than one twentieth the age of the continents proceeding to map the ocean floors scientists discovered a mid-oceanic ridge system that traced its way for 40,000 miles through the oceans of the world this ridge system is associated with volcanic and quake activity during the same period of research scientists were engaged in paleomagnetic surveys magnetic mapping of the Earth’s surface

the magnetic data presented scientists with puzzling irregularities or anomalies in this strip pattern in the North Pacific the dark area represents Rock magnetized in the present direction of the North Pole in the light areas the rock is reversely magnetized that is the North Pole is located where the South Pole presently is the results of all this research instilled a mood of unease and tension in the earth sciences by the end of the 50s the rigid earth advocates were playing a wait-and-see game yet any geologist who was willing to revive vague iners view did so at the peril of his reputation or at the risk of dismissal from his faculty the 60s commenced as a decade of synthesis a series of bold brilliant papers are presented by geologists who had seen in a flash of insight connections between all the unrelated data collected in the 50s Foos were heard at conferences when they presented their papers the late harry hess of princeton makes the first notable association between two sets of discoveries the mid-oceanic ridge system and his volcanic activity it occurs to him why the ocean basins are so young they are constantly renewing themselves rising from the hot limbs of the mantle lava is deposit at the surface and spreading laterally the seafloor then acts like a conveyor belt Frederic vine explains his discovery a connection between those magnetic reversals and Hess’s conveyor belt which determines the speed of seafloor spreading oceanic crust at sea floor is continuously being created at mid-ocean ridge crest such as the crest of the mid-atlantic ridge here in the South Atlantic it is generated above an upwelling in the mantle and spreads laterally away from the crest thereby separating drifting the continents apart as though they want to convey about supplemental material so one might represent this therefore by simple models such as this illustrating the way in which the conveyor belt of oceanic crust and upper mantle material flows out from this central crack in the Earth’s crust when our 1963 drum Matthews and myself then at Cambridge added the simple rider to this and in fact converted his conveyor belt of oceanic crust into a tape recorder we suggested that as new crust is formed solidifies at a ridge crest frozen inter will be the current direction of the Earth’s magnetic field this will be subsequently moved aside as newer material comes in and in this way successes avenues of crust normally and reversely magnetized will be built up paralleling the ridge press and symmetrically disposed about it and indeed in going back to the anomaly map the very detailed contour map arrest and Reformation for this area the Northeast Pacific and after peering at it for some time we could see that indeed there is a remarkable symmetry of the magnetic anomalies about the crest of this so-called wander Foucault Ridge in this area and they do indeed reproduce all the details of the reversal timescale in remarkable detail so to summarize this then we drew up this new colored summary map which emphasizes this symmetry about the rich crests in a truly remarkable way it’s readable to think that it had been within the literature for four or five years and 63 it was very frustrating because I have this idea and one realized that if it was true you know the implications were enormous the ocean basins were young ephemeral features that all the oceanic crust all the deep ocean basins that we see today that were generated say within the past 200 million years of geologic time less than 5% of the whole of geologic time but what of the earthquake activity associated with the ridge system – so Wilson provides the answer to the last part of the puzzle I remember being told as a student that the San Andreas Fault had an earthquake slot and they continued out to sea for some distance and then stopped abruptly so there’s a problem as to how a fault with large movement which the Californians had suggested amounted over the many years too many miles of movement in this sort of fashion could have motion like that which would stop suddenly somewhere out in the Pacific Ocean and the idea occurred perhaps something was going on as you can see on this piece of paper and you see this printing is taking place along here

where the material comes up to the surface and as the material comes up it allows sliding to take place along this line here so spreading here sliding here so the Pacific plate is bounded by the East Pacific Rise which is spreading by sliding along the San Andreas Fault another little bit of spreading off the coast of British Columbia in the state of Washington by sliding off British Columbia and then by subduction zones where the Pacific floor goes down under Alaska and Japan and North America is part of another plate so this was the origin of the idea of the transform fault and the continents are not being carried round as ships that are driving themselves but a drifting around on the surface of these huge plates as rods and the Earth’s surface is divided by these active zones where earthquakes and volcanoes occur into a number of separate rigid plates a little more mopping up with the aid of a computer and the ancient annals of drift are recreated scientist warren Kerry who first proposed using the edge of the continental shelves to make the fit more accurate testified I have even returned to vagueness Pangaea and so had they all by the end of the sixties but a lot of people aren’t happy about it because they weren’t brought up with it it’s like asking a middle-aged man to change his religion and they don’t really like it they would be delighted to see something happen that would destroy it all and go back to fixed continents there is a final irony the earth scientists still do not know what the driving mechanism is that propels the plates in which the continents ride in vague iners time he was rejected because the forces he tentatively suggested were insufficient the Newton of drift theory has not yet appeared his absence need cause no anxiety the theory is still young it is probable at any rate that the complete solution of the problem of driving forces will still be a long time coming it is only by combining the information furnished by all the earth sciences that we can hope to determine the truth this conviction gave me the stimulus to continue at times when my spirits failed me in 1930 Alfred Wegener died after setting out on skis over the polar ice of Greenland when his body was found a year later he did not appear to have died from either cold or hunger but rather from exhaustion

the film you’ve just seen depict sorry clearly the very important role that Alfred Wegener had in the development of the theory of continental drift in the early part of this this century the theory of continental drift is now part of the history of geology insofar as it’s been superseded by plate tectonics continental drift really treated only the continents as pieces of a jigsaw puzzle but now plate tectonics treats the whole of the Earth’s crust the oceans and the continents as pieces of a jigsaw puzzle so the program today looking at continental drift is in a sense a flashback to part of the development of a current theory one of the important events of the 1960s which stimulated a gun’ attention to continental drift was a meeting in London I was fortunate enough to be a graduate student in London in 1964 when the meeting was held at the Royal Society and the result of that meeting was this volume a volume of papers by those who were a Darren’s of the theory of continental drift and also some by those who weren’t and particularly some quite vigorous discussion by those who were in favor of the stability and the permanence of the continents and the oceans at that time this is one of the maps that was produced showing the fitting of the continents a map produced by some Cambridge geologists it’s interesting to reflect on the tremendous change that’s taken place in geology in the last 11 years that map which was produced by the Cambridge geologists was a map of the fitting of the continents particularly of South America and of Africa it wasn’t the first time that an attempt had been made to match those two continents it was first suggested by bacon and SiC the sixteenth 1600s and was repeated again in the 19th century by Antonio Schneider who produced some geological evidence a matching of fossils across these two continents in fact plants from the Pennsylvanian system but unfortunately this was the only scientific argument which Schneider put forward in support of his matching of the continents he felt that the split had taken place during the time of Noah’s Flood and this mixture of geology and theology didn’t win him many supporters in the scientific world even vagueness 50 years later who was the first undisclosed vagueness great contribution the first to marshal scientific arguments from many areas from climatology and paleontology and geology the matching of starter from continent to continent even then Wagner had a hard time because he was unable to propose a mechanism one of the things that Vigna was able to do was to produce a pretty good match of the continents but the match which was produced in the 1960s was a computer match and was very much more accurate it wasn’t just based on eye although the eye is a very good instrument for making comparisons of this kind the computer was able to fit these two continents together with an accuracy of 99 percent the average overlap or the average gap was about 90 kilometers which isn’t very much when you consider the size of these two continents now you remember from earlier units that the edge of the continent and the edge that was used to to match these two continents is not the coastline the coastlines are marked here in black the edge of the continent was taken by these Cambridge geologists as the 505 m line in other words 3000 feet or a thousand metres and that was taken as a true edge of the continent there are some areas of overlap and some gaps as I mentioned one of the areas of overlap is in fact up here and that’s where the Niger River into the South Atlantic at about this point and the Niger River has built

itself a Delta or Delta of sand and mud which has crossed the continental shelf which is very narrow there and built out and produced a protuberance or a watt if you like on the 3000 foot line on the 505 online it was used to match the continents and it’s for that reason but this overlap is here some of these small gaps can also be filled or if not filled at least made a little narrower by looking around for islands or a small islands of continental rock of granitic rock which are now in the ocean for South Atlantic which divides these two continents now one of the people attending that conference gentleman called Hurley geologist called Hurley from America from I think the Massachusetts Institute of Technology in fact went back to his laboratory and reasoned quite obviously that if these two continents fit that well then the geology or a match from one to the other the rocks oughta be identical and they oughta feet fit together like the the pattern on a jigsaw puzzle or like the newsprint that you saw being torn and the in the film and the particular rocks that he looked at that Hurley looked at were cratons areas of very very old rock areas of rock 2,000 million years old and older there’s an area of that kind in Brazil and one can see the perimeter of that that area rocks 2,000 million years old surrounded by other rocks 600 million years old Hurley found similar cratons in Africa in particular he found one here and there nearly all of the perimeter of that body of old rock was visible but it came to an end at the coastline of africa so Hurley reasoned that if Africa and South America war once joined it be possible to find the continuation of that crate on in South America so he went over and in fact right here is a tiny little area a very very old rock 2000 million year old rock surrounded by 600 million year old rock just as on the opposite coast he tested us again with another crate on this time again the main body of the crate on was in Africa but a small part of it was once again traceable in South America and from that kind of geological evidence the kind of matching of the geological strata ages of rock and kind of rock across the coastlines came the conviction that fitting together the continents like pieces of a jigsaw puzzle was a very good way to get some idea of the way the continents might have once been joined and it was as a result of that that further continents in this case yeah India and Antarctica let’s fit that a little better and Australia to move our countenance a little here not quite as easily done as the computer did it but nevertheless computer fits of the other continents in the southern hemisphere of Antarctica Australia and India produced not too bad a pattern particularly not too bad when you remember that Islands like Madagascar would fill up this hole rather nicely and the Seychelles are also islands of continental crust which fill up some of these gaps this major gap here which was a source of some concern and would be I’m sure to you looking at it that’s a very obvious gap that gap is produced because the defamation of this part of Antarctica is quite recent and was probably produced after the continents broke away and therefore the shape at the time that the continents were joined may well have been much more similar to the shape that’s necessary to match this coastline so that’s a bit of defamation after the movement away of the continents and

similarly one can explain some others of these small gaps down here now not to be outdone by the geologists of the southern hemisphere the geologists of the northern hemisphere also had a shot at fitting together their continents let’s take these off and put the northern hemisphere continents together Europe but cut at the Urals and North America and Bethan orally good fits were obtained for the northern continents North America Greenland and Europe and once again the geology matched across the the coastlines or matched across the the outlines of the continents once again these outlines drawn at the 500 fathom contour there’s a mountain vault that we know in the eastern seaboard of North America as the Appalachians which runs over into Britain Scotland Norway and touches the coast of Greenland a continuous mountain vault right across all three pieces of this northern part of the jigsaw puzzle now apart from the matching of the kind of strata much of the evidence for the former union of the countenance was paleontological and one of the that is was based on fossils and one of the main participants in the debate about continental drift one of the main authorities on the the use of fossils in matching the continents is dr. Karl Burt who describes in this next piece of film his interest in the problem of continental drift and the union of the continents or the evidence for the union of the continents based on fossils for the last 10 or 20 years a great deal of evidence physical evidence particularly has been accumulated to support the theory of continental drift the theory that the continents as we now know them have drifted to their present positions from an original from original positions which were far different now any theory to be viable must satisfy all aspects of the theory and for many years and quite a few years good many paleontologists people who study fossils we’re not convinced by continental drift because they felt that it didn’t explain the distributions of fossils any more than the idea of fixed continents and I certainly felt that way for a long time but as the evidence accumulated there seem to be more and more reason to believe in continental drift there was a problem though if you can picture in your mind’s eye the present arrangement of continents you remember that there is a connection the possible connection between Asia and North America in the Bering region there’s the Isthmus of Panama and of course that connects all of those continents and Australia is more or less connected that is their shallow waters between Australia and Asia and so it was possible to think or to postulate that animals got from one continent to another animals the past by these ridges and it’s a long way around that’s true but when geological time is taken into account that long way around isn’t particularly crucial because if an animal spreads its range by a factor of say half a mile a year in 20,000 years it will spread across 10,000 miles and that’s almost nothing in geologic time but Antarctica it seemed to me was a crucial key in this whole problem because here was a completely isolated continent now I had hoped for many years that perhaps fossils would be found on Antarctica that his fossils of land-living animals if so it seemed to me that would really clinch the paleontological evidence for continental drift well in 1967 in December a New Zealand geologist named Peter Barrett found this little piece of bone which just happened to come to me for identification this happens to be a piece of a lower jaw of a big amphibian

that lived in lower Triassic times and here was a first clue that there might be fossils on an arc to Antarctica that would have a bearing upon the position of that continent in lower Triassic times on the basis of this bone an expedition was organized to go to Antarctica to look primarily for fossils because this been found incidentally by a geologist who was working on other problems well it so happened that I went to Antarctica with several colleagues and we started collecting fossils and we found various pieces of bone almost immediately bones like this bones like this this happened to be a piece of a pelvis but I wasn’t able to completely identify these because they were not the crucial parts of the animal but on December 4th 1969 a date that I remember very well this piece of bone was found now this happens to be a piece of a little skull and here is a skull now if you look closely I think you can see that this corresponds with this part of the skull here is this portion of the bone known as a maxilla here is a tooth here’s a tooth now this is the skull of a reptile of fossil reptile known as a Dyson adopt found in South Africa this particular reptile is called mr. Soros and here for the first time we had an indication that mr. Soros lived in Antarctica I think the correspondence there is very close so that was really the beginning of our good hard evidence as to the nature of the fossils in Antarctica well subsequently a lot of things were found for example here are the bones of a large lister Soros the shoulder blade leg bone piece of ribs and foot bones too profound in Antarctica and here is a specimen which it may be a little difficult to see nevertheless this is a crucial specimen because here is a skull cut right down the middle by processes of erosion of Alastor source of about this size you see here here is a tusk here is a position in the eye here is the back of the skull here is the bottom here is a topple and those correspond like that so to make a long story short we found a great deal of Tyrael representing mr. Soros in Antarctica now this Casares is a characteristic muscle of Lord triassic age found in South Africa found also in India found also in eastern China and it lives along with various other reptiles that were contemporaneous with them with it for example here is a little a skull of a little rep full moon was pre color foam from South Africa in Antarctica we found let’s go four caliphs on and I think can you see those I think it’s quite obvious that those are very similar indeed this skull has been smashed down if it weren’t smashed it would be very close to the other one we found a whole skeleton of this and indeed we were able to reconstruct the skeleton of this little reptile from Antarctica which could be seen in this drawing and a skeleton from Africa seen in that drawing and you see there’s the evidence of animals that were almost the same living in Africa and Antarctica animals like that for certainly land living animals see the feet and they couldn’t swim across great expanses of ocean so I think this is good evidence that on Antarctica was closely connected to Africa and indeed that these animals represent individuals living in a single range the range comparable say to Eastern North America in the areal extent it subsequently has become split apart by the drifting of Antarctica and Africa only each from the other so those are members of the lystrosaurus phone as we call it and there are various other reptiles also belonging to this association of animals but the characteristic thing was lystrosaurus as shown by these bones and as shown by this restoration of mr. Soros this shows what the look like and I think here again you can see that here is an animal that certainly wasn’t a swimming animal although we have reason to think that it lived along the edges of rivers and streams it was a very strange kind of a reptile and had this sort of a beak like

front of the skull it lived upon plants the evidence is pretty good for that and these animals are found by the thousands in South Africa as I say to found in India and we find the abominable remains of them and Antarctica so the discovery of all of this material certainly turned me around completely I was as a matter of fact pretty well convinced of continental drift before we found these but this I think really clinched the matter because here were animals that we’re obviously land living farms they had to go from Antarctica to Africa to India to China across dry land connections and I think this is good paleontological evidence that fits right in with the geological evidence to show that these continents were once part of a great supercontinent in the southern hemisphere called Gondwana land and I think this evidence from Antarctica is going to be very interesting as it is developed in the future we made two trips to Antarctica and I’ve just merely scratched the surface of a large continent of kauffman half again as big as the United States in extent and there’s a great deal of material of this type to be found in Antarctica and I think more material and better material will be forthcoming in the future and I think other types of land living animal animals will be found there also since dr. Calvert was in the Antarctic in the late 1960s not a great deal more fossil evidence has turned up there are obvious problems because of the climate and the amount of the continent that’s covered by ice and even the rock which is exposed is not the kind in which fossils are commonly found most of it is metamorphic and igneous and there’s not very much sedimentary rock exposed as dr. kovac pointed out it’s very important to choose the right kind of fossil when you’re matching continent trying to establish that they were once together and that the fossils were once part of one community it isn’t any good picking fossils which were able to swim across large expanses of ocean this Mesa Soros was one that like the lystrosaurus is thought to have lived in swampy areas and was quite incapable of crossing a hawaiian and therefore the fact that it’s found in many of the southern continents is a good indication of their form a union another fossil that’s been used for matching South America and Africa are the so called ostracods these are little shelled animals that live in swamps very very small like shrimps and they are only found in this area and this area and we know from their present-day relatives that the Lavi becomes sterile if they’re exposed to seawater so there’s no possibility of the ostracods having crossed from this continent to this continent across an open ocean the continents must at the time of these ostracods have been together and the dating of the rocks in which those ostracods are found is quite interesting they’re about 200 million years old perhaps a little bit older than that 110 maybe a hundred and twenty and in rocks that are younger than that we don’t find the same correspondence of fossils from South America to Africa it seems that these ostracods were the last to be shared by these two continents and it gives us a date for the breakup of this grouping of continents Gondwanaland as it’s called it seems that South America began to move away from Africa about 100 million years ago before that India had already begun to move and eventually collided with Asia Antarctica and Australia began to move as a unit probably just a little before the South Atlantic began to open up so fossils can also give us an indication of the time at which the continents began to move apart now there’s other evidence for the former union of these continents in Rock Sudan about 380 million years old and that lies in the distribution of the traces of glaciation an ice age in these continents about 450 million years ago these colored pieces representing the area in which we find traces of glaciation in 450 million year old rocks now of course as the continents but

presently situated with India farther up here and these two separated and talked to go down here Australia over there it makes no sense at all but if we put them back together again and close up according to the geometry of the continents then this area and we think that Antarctica has the same traces of glaciation but of course it’s much hidden by ice and we don’t have very much evidence this describes a very nice kind of polar glacial ice cap about 450 million years ago also evidence for the existence of this grouping of continents at a certain time we think in fact that this grouping Gondwanaland formed about 500 million years ago and began to split about 100 we all began to split about 180 million years ago and finally split into all of its fragments about a hundred million years ago now there’s also good evidence from paleo magnetism which perhaps you remember from oceans that the continents have moved it’s just deal with two of them and look how that indicates that the continents may once have been united you remember that when igneous rocks cool they assume as the iron minerals such as magnetite cool through the so called the Curie point at about all five hundred and eighty degrees centigrade they assume the direction of the Earth’s magnetic field we talked about this in oceans and when the continents were united we can assume that they would all the igneous rocks cooling in a particular time would have the same direction frozen into them they would point to the same North Pole if we collect rocks of identical age today from Africa and South America we find that rocks are the same age point to quite different places very very separate positions for the North Pole of let’s say 400 million years ago but if we put them together again according to their geometrical fit to their jigsaw fit we find that they point to the same North Pole and this can be done with all of the southern continents and also with the northern continents and it was this evidence from paleomagnetism that finally clinched the theory of continental drift stay tuned for a short public membership break you can show your support for TV Ontario programming by calling in a financial donation at four eight three fifty five fifty five from