Hi.  Thank you all for coming.  We are as usual,  really stressed for time. because at one point people started coming  in from another class. [intro inaudible or not necessary] Professor Jason Morgan, he has been with our department for many years.  He has since moved to become a visiting [   ] at Harvard.   He's going to tell us of about 50 years of us about 50 years of plate tectonics.  There is a monthly memo floating around here, I like when one of the faculty shook George W. Bush's hand and called him an extremely charming man.   and he is an extremely charging man. He also shook the Emperor of Japan's hand and his hand was larger than anything that was ever seen before. This is, plate tectonics really is as you all know a revolution in our times and we are so fortunate that there are still people here to tell us that story and what we have learned since. So without any further ado, we have Jason Morgan.  Thank you. Bob was here at the very beginning. I was one office down and across the hall from Bob. He was the second chief physicist here after Bill Elsasser. I think I was the third. So what I would like to do is, different and it's really not to say so much what tectonics is and all. But, as I was thinking about this, why I was involved? I think some of my background really set me up for this. And of course, the most important thing in my background is that I was at Princeton. That, this was one of the few places in the country where you could say continental drift and not be carried out of the room. [laughter] I'll get to that part. I was fortunate enough to have Harry Hess was here with me and Fred Vine and Walter Elsasser and without this combination, but I think it was part of my previous education and all that let me get ahead of the crowd on this. Dan McKenzie in an interview with Naomi Oreskes said that if plate tectonics hadn't been discovered in '67, there would have been five or six people that discovered it in '68. I believe that's absolutely true. It's what gave me a head start is what I'd like the first part of this talk to be. This was the first map. You don't know how to make maps like this. You had wax paper with patterns on it and you'd press it down and rub it in real tight, cut with a razor blade around the edges. You didn't have computer graphics. You did it on a piece of paper and the lettering also was quite, a it took a skill to write letters, people could read. So I'll start... I think for me what started was, I took trigonometry in high school and it was not required. You had to have plain geometry, you had to have advanced algebra. I didn't get calculus until my sophomore year in college. That first two years at the engineering school, you took advanced algebra and trig and analytic geometry. But, I had had trig in high school. High school Trig is very, very different than college trig that it's really all about logarithms because you.., multiplication was hard. A lot of errors in it and multiplication was generally done with log tables. You didn't.., you'd have to look up a value of the sine or cosine or something in a table. Why not lookup the log of that. Then you can just add that number to the log of say, the hypotenuse and take the analogue. So these are different log tables. The one on the right is of, you know, they're sines and cosines and tangents. And you go through this. It is difficult to multiply five digit numbers, very error prone. You can add them pretty accurately. So logarithms were common. George Washington knew how to multiply. Probably one of the few early presidents that did. Multiplication wasn't taught in normal school systems until about 1850. They had required education and they had to have something to fill up the time. And they did more than just add and subtract. In like, third grade now, you learn to memorize the multiplication tables. But he was a surveyor and he'd do logs and he could multiply. This did not exist until '65. And then they cost quite a bit. In college, I had a slide rule, just like that, it cost $25 had a nice leather case. And you could do three or four significant digits. That it works on the principle of logs and college trig is very different.  High school you learn log tables. College you learn these identities that you're going to need when you finally take calculus. So I had that background and my teacher, we had two weeks of spherical trigonometry, which is very similar, but different rules. I had, I'm probably the only one in the room, that's had a course in spherical trig [laughter]. That turned out to be very useful. One of the interesting rules is in planes. The sum of the angles is a 180. That's not true on a sphere. The sum of the angles is this 180 plus the area of the included area. As an example, here's the triangle that has three 90 degree angles. If you go down to the equator, along the equator 90, and this is 1/8 of a total sphere. The total sphere is four Pi. So essentially  it adds up that this triangle has 270. This all came into play. The other thing I had is in the Navy, I had a navigation course. I knew all about map projections. That was a big part of it. You have basically cylinders that you say put a light in the center and project out than you unwrap the cylinder or you have a cone. You can do strange things by stretching this to, to have angles true or have area true or there are tricks but they're basically only these three. The very special is the Mercator. It started with a cylinder, but you stretch up and down exactly the amount that those lines are getting further apart. That up near Greenland you can see that going 20 degrees in longitude is really quite a short distance in miles and you have to stretch vertically the same ratio. With that, you, can use the same compass anywhere on a chart. You don't have to have a special different shape to give you what angles are when you lay it down on one of these maps. Is there a question on this conformal? The Mercator is the most important discovery in navigation map making. It gave the Dutch quite an edge for a while after Mercator, a Dutchman invented this projection.  [inaudible audience speaker]  [laughter] It gave the Dutch a big advantage that they could read Flemish. This is a gnomonic projection. It's one of these many things, it's also called the great circle projection. It's done by, if you look at the one on the right, you can do that. You put a light in the center and project on a globe. And that... a line that goes through the center, makes a great circle around the globe. The Equator is one that goes through the center and goes around, or these meridians do the same thing. But if you project that plane onto another plane, two planes intersecting as a straight line. The map is quite distorted, but any straight line, the equator, or any of these meridians, is a great circle and the others aren't. You do such things as the drawer of a ship there, 5-6 maps of the World down in the bottom drawer, that are these gnomonic projections. And if you're planning a route from San Francisco to Yokohama, you draw a straight line on it. And then you read off what each latitude and longitude is along the way and plot that on a Mercator map, and then that's what you used to go your course. So, I was familiar with this. The next part of what I think gave me the edge, is I was, very early on, learned how to use computers. This  particular UNIVAC computer is in the Deutsches Museum in Munich. When I saw it there.., this is exactly the type computer that I learned to program on at Georgia Tech, my last part, half of my senior year, I took a computer course. It was all ones and zeros. You would write an action and you would write addresses and you had to remember that number I want is in location 423 on the computer. and I would like to multiply that by the one that's in location 600. You had to keep track of all of this and you'd say add this and add that and store it here, or subtract or multiply. But I had a start in computers. This is the outside. It has 5,000 vacuum tubes. They are on the outside because that keeps it cooler, the heat can escape. The inside is where all the wiring is. that connects however you're supposed to do this. On the floor were the memory devices. This is a memory device, weighs about 500 pounds, as I remember. It has mercury tubes in it. The way it worked is there would be a little transducer at one end that would send out a pulse, a little piezoelectric crystal. It would travel down the lane and be received at the other end at a given time. It knew the memory because at the right time it would look at what had been sent earlier. It's what.. You would then either start it again, so that the memory wasn't erased, or if you were going to change a pulse to a non pulse or something, you would start a different one. This was.., it took about two seconds, pardon two milliseconds to, ..that was the machine sort of cycle time.  You could do... That's a very slow access time,  I'll tell you. But computers weren't very big. The total memory was...,  you had seven of these, and each one had 18 channels and each one channel had ten, sort of words that went down. The next... This is the first computer at Princeton when I got here, this 650 was on campus in a room, in a house on Nassau Street, one of the little wooden houses on Nassau Street, near where Thomas Sweet Ice Cream used to be. You don't even know about that. IBM really had planned to only make and sell about 50 of these. They actually made,  a couple of thousand and it cost about a million dollars. I think the much smaller, slower UNIVAC was more than a million. What really changed computing, was the invention of these ferrite cores, these little rings that you could put a needle through and wires. You would send a current through, and it would magnetize the ring. And if you put another pulse through in that direction, the ring wouldn't change. It wouldn't be any kind of flip that you would measure. If you put the pulse the other way, it would, flip and it would, be a signal that could get picked up that bit changed. With two sets going like this, and each one of them only carried half enough current to make it flip. All the ones that that this went through wouldn't flip except the one where there was another current, and that way you can have a specific bit in the machine that would flip. This was very, very fast compared to the, say, mercury delay line or the rotating drum that was on the 650. It was quite cheap, they were only a penny per bit. Now, it wasn't a $10,000 that would hold a few 100 bits. This was, boy, this was, pretty high. Now to tell you what a penny a bit is, this little SanDisk has eight gigabytes, and so it would only cost to make one of these cores, it would've been $80 million. I mean, you just didn't have memory. You programmed very conservatively to save memory and such. Ok,  next part of my education was in the Navy. I was an instructor at New London, Connecticut Submarine School, teaching Physics to sailors that were going on to the second or third Nuclear submarine, the Nautilus had already worked and they were all trained in Pittsburgh at the Westinghouse factory. But the Navy wanted to do it itself. I was a new physics graduate from Georgia Tech and my active duty was coming here. Lynn and I wrote the lesson plans that later I saw when it was printed as a book. They were still using a lot of what we, what we wrote by hand, and were out notes that we taught. There were a lot of demonstrations. This is a demonstration in optics, the focusing of light. What we went through is very quickly got to atomic physics, a little nuclear physics. The key was they'd know what our alpha ray was, our beta ray was and our gamma ray was. So they wouldn't be scared of them. We didn't teach them that much, but they weren't scared. So, I posed for a navy photographer. That's not me in my uniform, that's me in my midshipman uniform. I didn't find one when I was an ensign. I don't have a coat on, you do not wear a navy coat when you're standing in front of a blackboard. [laughter] That didn't last very long, so it's on a coat hanger. Here's my coat. Now, why I bring this up is while I was there, a recent PhD graduate from Notre Dame came, he was a math graduate student on his way to a job in the math department at Tulane. But he had his two week summer active duty. He came and gave us some lectures. He talked about an analytic geometry class that they had developed at Notre Dame, where everything was done in terms of cross products and dot products of vectors. You didn't have rules for defining the points, the formula that was a plane or to find out how to intersect a line with a plane or what the angle between two planes...   These things that I had had are.., is difficult, but they did it all with cross and dot products. It's amazingly simple. You don't have to memorize anything except what a cross and dot product is and use your geometrical intuition. This was extremely important when I started working on spheres, of being able to calculate small circles, and calculate great circles. This was really a necessary step in my education. And of course, as a physics graduate student in Frist just up the hill here, before it was the student center, you learn Euler's theorem. You rotate, you can get something anywhere else in a particular orientation just by a simple rotation. This is a key to the dynamics that you used the linear forces to get linear accelerations and you used the torques of the center of mass. You use the torques about the center of mass to, get the angular accelerations and such. And it's a key breakdown that mechanics didn't work. This simplifies it all. My thesis was related to geophysics and astronomy. A lot of orbits of planets. One of my two job offers was to go to NASA to work on orbits of satellites. Instead, I took a job as a post-doc here with Walter Elsasser. That's because I still had about three more months to finish my thesis and didn't want to leave town until... I didn't finished until  November that year. I didn't get paid until November. But that was my reason for staying. I had published a paper in JTR already. My first JTR, my first, American Geophysical Union meeting was in Washington, related to, this topic and learning about how the rotation of the Earth gets measured. Ok, now we'll transition into the sea floor spreading and all. What I  think set me up so that I could be there to take advantage. That there was a real explosion at the end of World War II in the US oceanographic effort that before 1840, there were only three US sea going oceanographic ships. And one of them didn't last long. [laughter] It was the Carnegie, it  was operated by the Department of Terrestrial Magnetism. It really went for several years. A wooden ship is ideal for making magnetic directions to see how wrong the compass is, or what the strength is. But there are disadvantages of a wooden ship as that shows.    But after the war, there were all of these more ships. This is a seaplane tender. It had all the the machine shops aboard to overhaul the PBY engines and to maybe make rivets of little pieces of aluminum where there happened to be holes in the wing or whatever. It was essentially a floating hanger for sea planes and it carried fuel and other things they needed. You just sort of got the machine shop and you've got a bunch of science labs. And it's a nice small compact.., This one changed it's name from... I don't even give the number, but it became the Pioneer, which was a particularly famous research ship. With all of these ships and the Navy's great interest in knowing that the knowledge of the ocean is what really led to the demise of the German submarine fleet. The sonars and knowing about the temperature inversions and all of this. Now, there were a lot of tools and many, many things were suddenly studied, and being studied by a lot of ships. Among the things that was learned, was the bathymetric chart of the ocean. This is the Herzen & Tharp map. The original was only the North Atlantic. This is a later version and it shows the whole World. In particular, I'll talk about the Encino Fault. Maybe the Altanic  fault down here. But you really saw the depth. Another thing that once you had this ridge, this rift right down the center of the Atlantic mapped in discovery. This is where all the earthquakes were. In the oceans, that the location is accurate to 100 or so kilometers back then. But they were very few that are not down the middle of the ocean. And this was Herzen came here and gave a talk in '58 or something. Dephase and Hargraves said, Hess was extremely excited over the talk, and made comments about it after it was over.  Another important thing, and this talk by von Herzen is said to be the immediate predecessor to Hess coming up with seafloor spreading. Is that a way to measure the heat flow by dropping something into the mud that had a bunch of a thermometers at different depths in the mud, in seeing what the gradient was, calculating the heat flow that you have this spike right at the crest of the East Pacific Rise. This is not the original figure. This is a much later figure. I can't... The 59 is a paper that doesn't have any figures of data in it. It's just a little short nature note. But, in his talk he had a figure. So, this was [inaudible]. This is Hess. He, in the 1930s, was aboard a submarine with Maurice Ewing, measuring gravity in the Caribbean. To get aboard a submarine back then, these were military guarded these with great privacy. And you had to be an officer and also so the captain could give you orders, you couldn't do something the captain said no or that was it. So here were these two people that joined in '35 and were aboard the Barracuda and did this survey. But in '42, they go through, oh here's someone that was a reserve officer in the Navy. He was made a lieutenant because that's what, he had a PhD, and in the Navy, all of the medical doctors come in as lieutenants with two bars and one kind of doctor is as good as any other kind. So they were both officers and he was anti- submarine in the Atlantic. And when that quieted down, he went into the Pacific and became the captain of a ship, that made many crossings between Hawaii and the Marianas and the Philippines and such. He kept his depth recorder running all the time. He was curious and this is, a depth recorder example from the ship was the Cape Johnson. It's the first guyot. It's actually a copy of a little postcard that the department had that you would mail to get reprints from somebody.  There were no Xerox's. So you read a paper and thought it was interesting. You wrote the author and say please send me a copy. When you published your paper, you would, you would pay a little extra and get 4 or 500, pardon, 50 or a 100 copies of that. When people sent you cards requesting, you would send it off. This was the Princeton card The one from Woods Hole had a picture of the Atlantis on it. Their ship. In '60, Hess wrote this, came up with sea-floor spreading that all of this continental drift and things moving and continents plowing through the oceans, and crumpled up edge on the leading side and more stretched. That all gave way to this idea that it was just sort of a conveyor, ocean and continent moved together. It was converged in the trenches. There was spreading in the mid-ocean ridges. This was the model and this, this bolt at the mantel. It was sort of what we now call the lithosphere. It carried ocean floor, and carried continent. This was very much also an idea of Elsasser. He was very strong theoretical support for the idea that the upper 100 kilometers of the earth is very, very strong because it's cool and it's the same as everything else. His idea of stress channels and such. So Hess wrote a paper and it concludes with a list of 19. Said, if this is true, then, the following 19 things should be true. It really explains sort of everything that was important about the oceans. If he would have given this a grade. He missed two. He thought that the seafloor was serpentine. The dredges that were done in deep sea trenches brought up a lot of serpentine. What's under most of the floor, it's covered with mud and you never dredge it. So your exposure was really only at these fracture zones. Plus the land examples were all serpentine, but that's really because once they got up on land, the rainwater converted the peruitites into serpentine. But that wasn't known then. This is the kind of measurement that has to be done in the Caribbean. It was done first by Henning Menez on a Dutch submarine. This was quite striking that in the deep sea trenches were the, lowest gravity values that you've ever seen. On the islands behind it, they get to be very high. This is what I started.... This is Hess's cruise in the Caribbean and Barracuda Ridge is out here, which was the name of the submarine. But there was the idea of these tectogenes  that at least pushed they would form..., this was replacing earlier ideas on what caused mountains. This is very nice.. you couldn't, do lab experiments of convection, but David Griggs used a set of rollers to mimic the effect that convection would have and can make trenches or make the other kind of tectogene pictures. This is sort of what I was into and this was my first paper as a post-doc of Elsasser's. Essentially if you have something, sinking, it's very heavy, it makes a positive gravity. But it pulls down the surface above it. It has to be exactly as much mass deficiency here as mass excess here.  It has to be an exact balance. Or else if you had a box around this, the whole thing would accelerate. Your stresses in such had to be that, you know, it was in mass equilibrium. But, the top, when you measure, you're closer to the mass that's not there. You have a very strong low, and that overwhelms the [     ]. and this would be the total gravity. I applied this to profile of Puerto Rico that Lamont people had worked on. There were a lot of submarine experiments. There were a few gravity measurements. in Puerto Rico. The big deal for Lamont was there were 35 of these two ship refraction, where one ship listens and the other sets off, rolls depth charges. There were a lot of depth charges back in the early 1950s that they they age. They don't keep T&T in storage forever. I wrote a paper on this. I looked at the profile and said, well, all islands look very symmetric when you go across. So, if you have sort of just the island and what you measure in Puerto Rico, what you're left with is just this picture that you could match with the sinking mass beneath the trench. So, I have the mass access about 80 kilometers down, and a mass 100 kilometers down. You could explain this rather than the way that the Lamont people had done it by the appropriate wiggles of the Moho, contrast of the crust density and the mantle density. So this created a firestorm. I mean, I had insulted everyone at Lamont fiercely. I mean, saying their work was a bunch of crap.  Xavier was on of the papers on the North Atlantic. He's a very good writer. Very good friend.   My children carpooled with him to school in France. We were not friendly on this day. They came at me with Talwani, Ewing, Worzel. All of the people that Hess didn't like at Lamont and vice versa. But when I wrote a reply to their comment to my paper, I didn't answer their questions. I said just, this is just two different ways of looking at it. One is, it's all static, and strong and can hold it, that was their view. And the others that they're dynamic processes going on, and flow. And I had a quite short response. And, at the HU, that was, coming up when I wrote a paper where I had taken this to the next step and essentially had an asthenosphere, lithosphere, varied viscosity, not just a uniform viscosity going down. And I was scheduled to give a talk at a session that Vine was a Chair of, as well as, Bill Minard. But something happened that in January of 1967, Bill Menard published a paper saying that the great circles in the Pacific and he had written so much about were not great circles, as he had said in his book and all these earlier papers. To show they weren't great circles, he made it a gnomonic projection. That this is the great circle projection. That they're not straight. The clipperton is pretty straight, but not the others. I looked at this figure and all the ones on one side  sort of curve up, on the other side they sort of curve down. It looked just like the figure in my navigation textbook. So, I figured that there was, a point that they were all concentric about a pole. You can see here, that this is a cleaner version. These curve up.  These two that are nearest the equator are pretty straight, so, using the math tools that I now quickly experimented. This is sort of the third day after that, and a pole, about 78 North and a 111 East, somewhere in Siberia. If I draw circles about that, I can match these. This is a cleaner version of path. The other one is, you know, like the 9th of January after the paper was published on the 6th. To me there is nothing important about Siberia except the one thing is that in the Pacific, these practice zones are all concentric, about a common pole. So, I immediately went and tried to look at the Atlantic. You could see that they were concentric. This obviously, if they're opening more up here, and a little bit here, if you're 90 degrees away from that pole, you have the fastest spreading. And this.., I switched the talk I was going to give at the AGU, and talked about this instead. But the abstract said I  was going to talk about the other. Well, most of the people left the room because I was the last talk before lunch break and it was already 20 minutes past noon. So I had a rather small audience. But, Xavier Le Pichon was in the audience because he wanted to be able to comment on what I would, you know, the sort of feud that was going on. He's really the only one in the audience, I think that took this. I gave a copy of this paper to Menard. He says at one point, he shared amongst students at Scripps. Dan McKinsey never saw it though, when he came late. So this was essentially the start. I did more than just the Atlantic. I could look at the, strikes of faults along the San Andreas or along the Queen Charlotte up to Alaska. And it's not as good, but it's the same basic idea. This is Antarctic, there are big fracture zones. They, sort of have an intersect here and you also, you find sort of the distance where it is, by how the spreading rate changes. This was the a, this was the sort of final paper. My conclusion is that the continental continents had rigidity was just implicit in continental drift. But that the oceans did, and never deformed once they were made was essentially proven by this, that it was a test that if oceans were deforming, none of this would have worked. Okay.  So, I would like to skip almost to the very end. There were telescopes that were used to measure distance. You would get noise from a pulsar at two places. You would tape record them at both ends about five minutes looking at both the same star and then they would slew and look at another star, and look at another star and you could get the distance.  It took these giant dishes, they eventually made something portable that would fit into two semi-trucks and you could carry it to exotic places of the earth. There was a satellite that was only about 300 glass reflectors. You had lasers that set pulses and you'd measure the round trip. You could triangulate places on the Earth if you look simultaneously at a bunch of stations. This is a GPS satellite, to show you its complexity. Also, to show you its cost. It's an incredible instrument for a lot of things. But you can measure, really to sort of over a data of millimeter of accuracy. The beauty of GPS, is the receiver. You don't need a radio telescope. You don't need two semi-trucks, it's all about 50 pounds and half that is the tripod. But this is the first data that came out was from Westwood, Massachusetts to a town near Munich. This is every five days they made measurements. This same pattern of stars. The red line is not a fit to the data. The red line is a prediction from all the magnetic anomaly in the oceans. You measure 17.7 millimeter per year separation of these two points, one in Europe, one in Massachusetts. Magnetic anomalies said that should be 18 millimeters siare. This is between Westford, Massachusetts and Richmond, Florida. Richmond is just south of Miami. There was a telescope there, used by NOAH, but it blew down in Hurricane Andrew. They never put it back because they had other ways of doing these  kind of measurements. There is 0 change. These are both the same plate. there is no motion. I mean, the rigid plate really fits. This is Fairbanks, Alaska to Hawaii. You have a conversion grade again The difference between the magnetic 45.4, which you measure 45.5. Plate tectonics really, really, really works. This is more of a map view of this. But now you have GPS and lots of it. Its become much more complicated. Things that you could never do before, like Tibet or Turkey, It looks like a rigid motion of sorts. But not exactly. This is the western United States and everything out here, the dots are so small you don't even see them. Once you get past the Wasatch front its an ever, ever ever faster. When you get into western Nevada, it's moving pretty close to a centimeter a year away from the basin range is spreading. Surprisingly, all of the Central Valley of California is, is moving north, at one or two centimeters a year compared that sort of an Owens Valley, kind of separation between North America. Then you have a big step when you cross the San Andreas. This is the current GPS stations in the US. It's thinned out here because these stations have been gradually moving east. I show this because these are the best-fits they measure. You can see that it's pretty much just a rotation of the entire plate. If they subtract that out, this is a figure by Tom Davis whose a grad student here and a couple of others. This is just noise at the level your instrument, sort of measure, when you get near Canada, you can see the rebound from the glacier, that it's really, you have a technique to really do this.  So you come back that, Hess's idea of really strong is correct. The idea of rigid is no longer needed because you actually measure this. Before, making a prediction was all you could do. There was no test how well the predictions was until there was this GPS. Okay. Well, thank you. [applause]