flinn@seismo.UUCP (E. A. Flinn) (03/14/84)
----- I've had several requests for more on the development of plate tectonics in the Soviet Union, so here is an article on the subject. First for some general history. You have only to look at a map to see that tectonic features have some peculiarities: mountains usually occur in rather thin chains, and volcanoes and earthquakes usually in long narrow zones, and the earthquake foci lie in planes dipping downward at angles like 40-50 degrees, and stop abruptly at a depth of 750 km or so. Why this should be the case was a puzzle for geologists for a long time, particularly in view of the fact that volcanic rocks are to be found pretty well everywhere, and extinct volcanoes in such unlikely places as downtown Edinburgh and central France. Moreover, the fit of South American into the bight of West Africa, and of North America into northwest Africa looks suspiciously like a non-coincidence, a fact which has been commented on for at least two hundred years. In the early part of the twentieth century Alfred Wegener, a meteorologist, wrote a book on "continental drift," which is a splendid book - Wegener was a keen observer. Unfortunately he was unable to demonstrate a physical mechanism for making the continents move around, despite some ingenious hypotheses. In the 1920's Sir Harold Jeffreys (the 'J' in the WKBJ method, who is still living and who still does not believe in plate tectonics) showed on the back of an envelope that the continents *cannot* have moved by ploughing over or through the oceanic crust, since if the crust were weak enough to allow this, it would be weak enough for volcanic islands to sink out of sight in times like 10,000 years. It was not only Jeffreys's personal prestige, but also the force of this objection, that kept almost all geologists from taking continental drift seriously. A very few southern hemisphere geologists kept pointing out that the geological formations in Africa actually matched those in South America, and the appropriate action by the geological community would have been to buckle down and *find* a mechanism by which the two continents were split apart to their present positions. Human nature being what it is, the whole question was roundly ignored for many years. After the second world war, a lot of new data began to be acquired. For one thing, paleomagnetism was perfected to the point where remanent magnetism of rocks could be measured (you form a rock, sedimentary or igneous, in a magnetic field, and the magnetic domains align themselves with the direction of the ambient field); disturbingly good evidence began to accumulate that older rocks formed at magnetic latitudes quite different from what they are today, and that the pole position moved more or less smoothly over periods of hundreds of millions of years. This was ascribed to "polar wander," or movement of the magnetic pole itself, rather than admitting that the rocks may have moved. More disturbing was information on earthquake epicenters in the deep oceans, gathered primarily through the worldwide network of standardized seismic stations largely funded by the U.S. government as part of a research program in underground nuclear test detection - the epicenters not associated with deep trenches all track the mid-ocean ridge system, which military bathymetry had discovered during the war. Even more disturbing was the mapping of marine magnetic anomalies, begun during the war in anti-submarine warfare - these anomalies, where the ambient geomagnetic field is perturbed by magnetization of the ocean crust, are all elongated and narrow, and usually run parallel to the mid-ocean ridge system. Most disturbing of all was the fact that the magnetic anomalies are *symmetric* with respect to the ridges, the same pattern being seen on both sides of the ridges. In the early 1960's, several brilliant scientists (notably Harry Hess of Princeton and Tuzo Wilson the University of Toronto) independently and almost simultaneously saw the explanation - it is not the continents that move, but the crust itself. The crust of the earth is made up of "plates" a hundred or so kilometers thick; these plates move apart from each other at the mid-ocean ridges, where molten rock freezes onto them like ice on a windshield as the plates move apart. The plates collide on the sides away from the ridges, and usually one slides under the other, causing earthquakes and volcanoes at the collision zone. At transcurrent boundaries such as the San Andreas Fault Zone, the Alpine Fault in New Zealand, and the North Anatolian Fault in Turkey, the plates slide horizontally past one another. The magnetic anomalies are caused by freezing the rock onto the plates at the ridges, and naturally both sides of the ridge have the same orientation of magnetization. Human nature being what it is, these first ideas on plate tectonics were also ignored by most geologists. However, in a burst of activity in the middle 1960's, several young geophysicists picked up the ideas and refined them - Fred Vine and Dan McKenzie of Cambridge, Lynn Sykes, Brian Isacks, and Jack Oliver of Columbia - and suddenly it wasn't possible to ignore this any longer. For me, the clincher was Sykes's work on fault mechanisms of earthquakes on "transform faults," fracture zones where the mid-ocean ridges are offset. Looking at a map, the earthquake mechanism should be in the direction of the offset of the ridge: || -> || --------------- || <- || but plate tectonics predicted the *opposite* direction of faulting, because of the crustal spreading away from the ridges. Here was a - perhaps the - key experiment, and Sykes showed that the mechanism was indeed the way plate tectonics predicted. So the bandwagon gathered speed, and by 1970 the evidence for plate tectonics was already overwhelming. The only geoscientsts who hadn't accepted the basic ideas by then were a few oil company geologists in this country (Art Meyerhoff, for example), a few British geophysicists led by Jeffreys, - and Vladimir V. Beloussov in the Soviet Union. Finally the Soviet part. "Beloussov" means "white mustache" in Russian, and V. V. looks the part - a solid block of a man with a shock of white hair and piercing blue eyes. I doubt that anybody has called him 'Volodya' for fifty years. He is a member of the Academy of Sciences of the USSR and a former President of the International Union of Geodesy and Geophysics (IUGG), Chairman of the Soviet Geophysical Committee for many years, and the acknowledged leader of geophysics pertaining to tectonics in the Soviet Union. Like all outstanding thinkers Beloussov had had to work out a geological weltanschauung for himself, and his scheme was one of *vertical* movement - after all, mountains are high, etc. He wrote several books and many papers on vertical tectonics. Now, when plate tectonics wrought a revolution in earth sciences as profound as that done by quantum theory and relativity in physics, or evolution in biology, Beloussov, for reasons that I don't pretend to understand, decided not to go along with it. One little bit. Since 1970 or so he has fought a rear-guard action, arguing still for vertical tectonics and doggedly pointing out flaws in plate tectonics as well as data that don't fit the plate tectonics model. In this last he has done a nice service for scientists in other countries, by forcing them to sharpen up the model to account for his objections. Even today there are lots of things that don't quite fit - for example, we understand hardly anything about why residual stress in the middle of plates is still big enough to cause large earthquakes there, or how plateaus are made, or exactly what the balance of forces is that moves the plates (convection in the underlying mantle, the negative buoyancy of descending slabs of crust, gravitational sliding down from topographic highs maintained by thermal expansion at the mid-ocean ridge system, etc.). However, within the Soviet Union the intellectual and political climate was such that almost no scientist was willing even to betray any interest in plate tectonics, although I understand that in the Ministry of Geology there was more interest than in the Academy of Sciences. Beloussov's stature and power were more than enough to pretty well squelch discussion of plate tectonics, much less research on it. In the early 1970's I was an exchange lecturer under an agreement between the U.S. and Soviet Academies of Sciences, and I worked up about ten talks on different aspects of geophysics, and was routed around the country talking at different places. During the first week I scrapped all but the one on plate tectonics, and went around the whole summer beating on people to get them to understand that this was where the future of geological sciences lay. There was polite but restrained and obviously uncomfortable interest on the part of my Soviet listeners. Now, in the central research institutes at least, Soviet scientists are every bit as good as those in any other country. Their distress level rose higher and higher at seeing their geological scientists fall farther and farther being the main stream, and finally become almost a laughing stock. In the middle 1970's, A. V. Sidorenko, a geologist, became one of the Vice-Presidents of the Academy of Sciences, in charge of all geological sciences - a position of very great power indeed. Sidorenko saw that it was stupid to handicap Soviet science in this ridiculous way, particularly as it had become clear that exploration for mineral and petroleum resources depended critically on making use of plate tectonic concepts. He had the stature to decree a change of direction, and one of the things he did was to establish an Institute of the Lithosphere within the Soviet Academy of Sciences, bitterly opposed all the way by Beloussov, who was maintaining his own shrinking empire. Beloussov did everything he could, both within the Soviet Union and in international forums like IUGG and the International Council of Scientific Unions (ICSU), to hamper every effort to establish research projects to work on the new ideas. In 1970 ICSU set up the International Geodynamics Project (IGP) to coordinate research worldwide on geodynamics, i.e., the dynamics of the solid earth, which for all practical purposes was plate tectonics. Soviet participation was skimpy. One or two younger geophysicists broke loose from the geophysical establishment, still dominated by Beloussov, and attached themselves to Sidorenko and to plate tectonics. Unfortunately these people are not of high scientific ability, are divisive in international forums, and their naked ambition and toadying was pretty unpleasant to people in other countries. Anyway, by the end of the IGP in 1979, ICSU and the unions of geophysics and geology established a follow-on international project, the International Lithosphere Project (lithosphere is the jargon word for crust), which will run through 1989. I've had the good fortune to be Secretary-General of ILP since its founding, and it's a really exciting program. Soviet participation in ILP is quite strong, and now that it has become not only safe but profitable to be a plate tectonicist in the Soviet Union, everybody is. Poor old Beloussov is now almost isolated within his own profession, and he will probably die an unhappy and frustrated man. Sir Harold Jeffreys, on the other hand, now in his early 90's, is serenely above such things. There are certain things you just don't talk to Harold about, and plate tectonics and free oscillations of the earth are among them. So science moves ahead. We now know from deep seismic profiling that widespread horizontal faulting has taken place within the continental crust, and our model of how mountains like the Appalachians formed has been completely overhauled. We know that continents are made up of mosaics of little bits and pieces of continental crust slathered onto each other by the collision process. Cycles of plate movement are now recognized all the way back in the Precambrian. Computer-aided tomography using seismic waves is providing a way to map convection in the mantle. Comparative studies of other terrestrial planets are leading us toward understanding the evolution of the earth as a planet. Satellite gravity missions are measuring the geoid to an accuracy that allows us to look at mass distribution in the crust and mantle. Being a geophysicist just now is as exciting as it must have been to be a physicist in the 1920's. I've probably told you more than you wanted to know, but you can follow up the Beloussov controversy in a book written a few years ago by Walter Sullivan, the science writer for the New York Times. Any questions will be cheerfully answered. -- Ted Flinn
bbanerje@sjuvax.UUCP (03/20/84)
Thank You for the wonderfully clear exposition. You made the
subject matter very clear for those (such as myself) with no
background in Geology.
Perhaps someone with a background in biology could explain
Lysenko's (?) theories in a similar manner.
I am cross posting this to net.bio to catch the attention of
those who may not read net.misc . If you haven't read it yet,
definately check out the posting this is a follow-up to.
Regards,
--
Binayak Banerjee
{allegra | astrovax | bpa | burdvax}!sjuvax!bbanerje