Geologic Realms of North America

but the goal of the class is to to put the the number of the observations the things we talked about we mentioned some geology around here and there and I think it might be useful just to make sure that you get a sense when you look at this map of North America and notice the beautiful background that that zoom allows you to use we're going to look at North America and get you a flavor of where things are in the context of the geography and sort of what makes this continent but puts this continent together obviously it's not going to be an exhaustive class on that on the geology of North America but it's going to be a class where am ii okay no that is recording where am i want to sort of it gets you a sense when you look at the map where things are so you that same map but i labeled a few things that are red are we going to focus on and and and obviously I recognize North America this map is cold time and terrain which is a map that tries to look at geologic realms geologic areas but also puts the time part of those geologic areas and so it combines the tectonic setting and the time of these events so it's actually quite powerful and informative map and it is it is not a geologic map in the sense that it shows formations it just groups them all into the city in these time blocks it will talk about time in a second but if you look at the map of North America then you would immediately sort of start to be drawn into the red color that's up in the Canadian side mostly that's the oldest rocks that North America preserved and we call that the shield and that's the internal that's strong that Ratanak part as we talked about that is the the core of North America and some of the other continents like Africa for example that's what the S is so the shield is the is the first one that jumps at you now in our side of North America so in the US side we find the shield as well but it's covered by a thin veneer of rocks and that's that's usually carbonates if you drive around here you see the outcrops here and there of these carbonates and that's the that's that little P there that are marked up let's we call that the platform sequence it's a it's not a very thick it it can be a kilometres thick in a few places but usually it's much less than a kilometer thick deposits that are in our case all phanerozoic in age mostly Paleozoic age but underneath that you would find the shield I should go I should go there so that's the platform sequence there's an interesting feature a usually interesting feature in north america what makes us one of the continents that have some characteristics that sort of tell plate tectonics well the whole story is not complete and we'll touch on that and luckily that's one of the fantastic things the geology of michigan there's not much to show you but it has actually incredibly interesting a geologic history because there's a nearly five kilometre deep basin that is in the Paleozoic that sits right in the middle of this plate this continent and that hole in the continent that sucked down a five kilometers depth and that's a lot of deposition or environment that's in the middle of this rigid plate so this is not a plate boundary this just happens in the middle of the plate we call the inter chronic basis so we'll talk to that at the end see how much time I have as we get through these various classes the other ones that of course that are the features that are the most pronounced features that when you look at the map especially if you look at the property is labeled with the O that is the orogenic belts that we can still recognize as such the Cordillera we'll start with that on the the western side it's particularly well exposed in in Canada it makes up all of BC as you go up into Alaska as well but there's also split segments of it up in the in the US as well touch a little bit later on on the eastern side of the continents we find the let me close my door the eastern side of the continents we find an older origin the Appalachians we'll touch on that of course as well but it's an orgy which is no longer active today and but it's still recognizable as such and that's where our field trip would have gone and stuff that I showed you I'm touched on the extended crust over here that's the something that's is unusual takes place in the in the southwestern US that is not a characteristic we see all around the world it's fairly unique for the US but it's actually quite interesting for different reasons of how you actually extend and break up the crust and then much you have left we also have the bottom of sorry we all set that in there in the southern part of the continent the gulf coast we have some extension there in that region that's the source of the oil the drilling is targeted there because it's the right rock for for for for carbon and and then in on the east coast so beyond the Appalachians where xaloc Florida and the Carolinas we have these flatline young deposits that's this will be called the passive margin deposits meaning there's nothing it's a margin of the continent Tamar do you mean it abuts the ocean it's not a play boundary it's just deposition taking place and that's the plate margin on that map and so so I've marked them all up all circle of margin as well because I have the capability now and so those are the characteristic features of you look at the continent of North America and I didn't mark up all the other places but but most of these other places are all very similar they're all fall in those basic realms the piece would come all the way up to the the frontal part of the Rockies etc and and and so it gives you the first sense and I hope that you would see this map and start to get a story out of this map as it goes as it goes forward the other characters that we have to briefly touch on is this the fact that of course geologic time is long we've talked about deformation we never talk much about how long it takes to deform rocks and to do the thing and what this shows is this shows it's just the timescale let's that's me now there's the updated time scale for the TSA updates that every now and then that gives us the sense you know if you want to be a sort of a memorization exercise world it enjoy this one there are lots of names I think some things are very familiar others are not but they're one thing you should really have a good sense of I think as a geologist in general is the crude not the crude I should say the big break down to break down that we find in the Cenozoic the Mesozoic depending Zurich and the Precambrian times so the Cenozoic boundary with the Mesozoic 65 million years you remember that the dinosaur extinction no window the Mesozoic and the Paleozoic boundary is around 200 250 million years I round of these numbers and there are specific numbers I find that not useful because it's good to have a general sense it's well it's 251 but it should be depending who you ask the 250 is good enough boundary Mesozoic companions are by the way that's also a big extinction event it is the largest extinction events that we have seen on the planets so far the base of the Paleozoic is nowadays located at 540 million years that means that the Kami Cambrian explosion of life happened at that time so 540 million years ago now what's interesting to remember now of course is that that remains another 4 billion years of Earth history is not covered by these first three yawns and so the Precambrian time we lump at the Precambrian is this window of that goes all the way back to the beginning of for the earth for 45 60 million years we break that down in in in in eons the Proterozoic and the RTN and the Hadean this is not the class to talk about but you may have a sense 65 255 40 and 45 60 these are numbers that suits you in the back of your mind it makes geology the amazing feature that it is and what and we'll look at features that are characterized by Cenozoic mesozoic history of north america Paleozoic history and a pre-k me in history that's how we're gonna break up these classes we talk away through these two DS features so this is another thing that you might eventually want to print out or hang up somewhere on the wall it's always handy to look back and rest assured that most 99% of the geologists we need to go back into this - into the timescale to find out the details right most people know their little favorite area I mean I've worked a lot in the Eocene and I know that sort of around 50 million years is what the EU seen since but most people do not memorize this but it's nice to know came in on a vision Silurian and Devonian Permian the only Carboniferous Permian even memorize these things they they're useful but it's hard to live put the numbers with that and these are the graffiti is important but I want you to get the time sense of these origins because we're gonna look at North America they stuck behind me we're gonna look at the the the the one the failures of the Cenozoic Mesozoic one and they were looking at B as the other side I should use my other elements and to worry about this and it works in the mirror image the Paleozoic one okay right let's look at the D what's the side of North America I made a list when we discussed I will not discuss all these things there's no time to get to all these all these details and all these features but but I do want you to get a flavor of the things that are useful to think about we'll touch on these things in in a light way well look a bit at - yet look at the terrains we'll look at the at the Arc System we look at the transition to - extension and even the San Andreas Fault the mention again at the end of the extension or boundaries that characterizes the western side of North America okay so I put this map up every now and then so that's a it burns in your mind who are we gonna talk about so we're gonna look we're gonna focus first on this section right over here of the of the country that's the the western side of North America you can generally call it the Cordilleran system but there's a lot of features that are in addition to the Cordillera and the time on the side shows you that these yellowish colors is really what we are talking about so the yellowish and the greenish colors represent the western side because that's the Cenozoic and that's the Mesozoic okay I immediately put this up to get you a flavor of what happened in that Mesozoic to today this is a a map that is an analysis that was done on this paleo map with Chris Cortese but it actually tracks the arrows are there the the the motion of the plates over time and so the confidence obviously move around but you see interestingly enough that North America right over here is actually moving in a westerly direction even though the Pacific is subducting underneath that and so you get the sense that the plates of course are are not sitting there passively and get subduction zones but also the plates are moving relative to one another and that will come back later on and I know that my signal I should probably find a way to erase that annotating function there later that's a the the location of of margins also evolves in Israel in this absolute reference frame so that was the animation and the pictures on the side are the snapshots that Chris created that were actually but the map was based on that we drew that map and so it's a history the Mesozoic and Cenozoic is the history of the opening it's all run at one more time and I say that it's the history of the opening of the Atlantic Ocean that is really the characteristic feature of this part is we live in and in the in this case the eastern part of the configuration it's the closure on what we call the tethers open base and it's at the ocean over here is called deathless sorry that's the ocean basin that's between India in this case you see there now indeed a rapidly closing in Asia and so that the ocean basin is gone the Indian Ocean as we know it gets formed and the Atlantic Ocean gets gets formed they were in there before in that in that configuration so that's the characteristic feature for for understanding in Mesozoic and Cenozoic and everything that happens to reflects that but that particular part of the history as we go on to going in there see where my mouse goes right over here all right now look at the geologic map it's incredibly rich in in in in areas meaning we found a lot of features there that looked like this sometimes we're very much disconnected and remember the characteristic feature that mark made up the the Cordillera of the of north america was this concept of the there are these areas there are these these these these terrains as we call them that have inherently a good story to tell they all have a consistent geology but then you step across a fault zone and suddenly you're in an area which is completely different I mean a complete different geology this ologies the ages are different and then you do a little work and you step over a fault zone and you go into a nother zone and so what we discovered at North America the quit a year of North America a large extent all these colors that you see the greenish and the reddish colors these are all terrains these are blocks that were welded on to the North American margins as part of this closure sorry opening of the Atlantic and closure of this and convergence of the other one the Fuuka played a smaller played segment that was sort of being that's being subducted underneath this all the geology of Alaska and and and all the colors that you see below the blueish and and the purpose color these are all elements that were not part of North America this is all I don't know these are those terrains you see some names in them they're thinking terrain and we talked about and what they did we talked about once this Rand Elliott terrain that's what I mentioned in class specifically it's it's also the first one to really be identified and we find it in different spots we find in the u.s. we found it thankou girl island we find it up all the way up into into the rangel mountains of Alaska that's where they were first defined and then people discovered that these same rocks were found all along the margin of North North America and so the first characteristic feature of North America was this idea that we have these terrains it's just the map that I showed you it's a little less busy although it still has the same names of these terrains and as you have this closure this subduction that takes place on the North America the terrains that were sitting on the subducting plate came in obliquely not orthogonal II but they came in here's the margin and they came in obliquely to that margin and as they do so once they got that margin they were not subduct able they could not go down because they were buoyant and as a consequence these terrains got torn up that got cut up by these large-scale transcurrent faults that that characterized the geology of the Cordillera and that was the signal observation signature observation you found terrains blocks that were inherently internally consistent and then was a block next to it that has a completely open history but the boundary between those two blocks were typically are typically these large-scale lateral slip are strike-slip faults and so these a transcurrent faults is the characteristic feature that allowed it to be spread out all along the margin of North America so the Cordillera terrains are very complicated because first of all they're multiple of them people argue how many of them but they're not fifty people said there were 50 or 60 and a lot of terrains now as many of these trains were the same it just turned out they were spread out over very large area and that's why I'd looked such a jigsaw puzzle where the pieces are being cut up again and spread around along the side took us a while to figure it out but once we figured it out we knew what to look for you look for similarities even though they were otherwise very far apart these areas it was incredibly insightful and and a change of thinking about orogenic mount organic systems we realized that if you work along the trend of an origin to understand it I said I said those forward so it's a rains characteristic feature the Cordillera turns out to be characteristic for all origins we now start to we've applied that everywhere else the other thing that's a feature that I spend a lot of time on other classes do that of course is that we have subduction zones then we have also typically we get arc systems to go with that and we find of course in the North America ample evidence for for that process that also forms the terrains but also the process of subduction we find all these mathematical we typically find it there exhumed these are Mesozoic arcs and Yosemite is a good example Half Dome I think that's half dome up there actually you actually don't know it's all copy down probably it's a copy done I've done is rounder at the top so that's just this big exhumed deeper part of a volcanic system the volcanic system that's it at the top it used to be right up here is being eroded enough and now we're actually seeing the the deeper part the magma chamber system so the Sharra's are like that the the Cascades are like that on the map on the right the black areas used to share us they we find these these preservation of these cells of these blocks this is just the exhumed volcanic system today there's no active volcanism in the southern US in there most of the u.s. in many way until you get to the northern part of the US and into Canada of course we get the we have the the subduction system Mount st. Helens and the like are the active volcanoes today they are more throughout a pd2 the active volcano chain that is the modern volcanoes the the granite baffle is that you see in in many of the parks are the exhumed older system when we had this Mesozoic particularly Cretaceous subduction going on so the arc is present to its old are some places it's young today it continues today the process has been going on for for quite a long time now the structural feature that's particularly fun to look at is the fact that we have dish the rains we talked about but if you go more to the east then we get this beautiful frontal thrust frontal thrust belt that is the the Rocky Mountains the familiar Rocky Mountains that make these beautiful ranges in the US and make a spectacular limestone cliffs in the Canadian segment and again on that map that we showed before and you can see their mountain systems and runs right through here comes up through here and comes down there and goes that way and Peters out in the south because the extension takes over so I change this feature in the in the south and you know if youth camp maybe that's not a nasty shanell Crisfield cambree's not gonna happen you're sitting right up here on Michigan's field camp sits right over there in in Wyoming but the Rocky Mountains are the the poster child of understanding the evolution orogenic fault thrust bells and so well look about took a picture there we spent quite a bit of time on this but I often did not play it into a new context if you hear a strange snoring sound this my dog sleeping next to me she actually snores or she dreams sometimes I'm sorry about the the background okay thank you sorry woke her up and she falsely begin in one minute she's not not worried about that the Rocky Mountains and so he's the picture of that area that said that it would be very familiar for a field camp and at the bottom end is the very busy diagram that I told you about is that as you have a thrust and you have a new thrust the thrust are one after the other day the thrusts are multiple of these thoughts as you can see in there today I'll step away and they come up there's many of them in there and they follow the nice generally follow the nice system by the most easterly thrust are the youngest thrust so we talked about the piggyback that takes place we also talked about the fact that you have these rampant declines these fault Bend Falls many of them you see in this diagram over here is a good example right up here and so we see those structures are very well developed in this in this cross section this is a cross-section just south of where our field camp sits our field camp sits as it's right up here in this area might appear and so it's you see that all these features now in their real setting the Fallen thrust bells takes the thin veneer not high-grade rocks and low-grade rocks they just slice up the cover it's pushing snow so there's a somewhere from that side over here there's a a big push that push of course is the terrains that are being treated unknown on the western side and that pushes their phone and thrust belt and gives us this nice geometry more complication than what I'm saying and aficionados would immediately jump up because it's it's actually a very large far regional extent origin and some own questions like that is but the basic story is completely what I said it there's a bulldozer in the West that pushes things and moves it up to in this easterly direction according to the rules that we have and the picture of Lewis thrust is one of the frontal once one of the most frontal one so it would not be on this map the Lewis thrust it's a little bit higher up you have to go into can see I can't see very well somewhere over here but to the Lewis thrust is a good example of the most frontal thrust it's you've seen in H we dated that was with clay place in the fault zone and if you go there it's a glacier park and it's one of this these clipper that are preserved it's the eroded remnant of this big thrust that otherwise is no present except at the base there as we look at that it's again limestone the lime stones are usually very strong they usually stay this is a proclaiming in limestone however and that sits on this cretaceous sandstone so deeply cut thrust system the Rocky Mountains um okay that's the feature as we talked about in the context of geometry so what else well it becomes actually one of the amazing features of of this map of North America you have to look a little bit carefully at this map and I put a little square around it I put a circle around it as well you see D said these reddish colors that are popping up as sort of like like raisins in this in this in this sea of yellow and remember eating that the rest to me represents the old part became lien part of this mat that's the big the big strong red color red color behind me over here that's sort of there that's the the older part and you see these things coming up also in the middle of this sequence that is in in the fall and part of the Rocky Mountains right we are slightly away from the Rocky Mountain is instead map right here is the Rocky Mountain Front and then we see these features that are to the to the east of that the wind rivers black hills the Bighorn some of them have you seen some of them are used as monuments as you know and those are proclaiming rocks that are also structurally brought up to the surface but in a surprising manner these are we call this basement uplifts because we have false that apparently are very very very deep they go to great depth and they cut all the way through up to up all the way through the mo house and these fault systems may be as much as 40 kilometres depth and what they do if you throw a crudely draw this line through here it falls owns of course or not a perfect zone but what you have is that these blocks are proclaiming rocks are brought up pushed up by reverse faulting but this reverse faulting is opposite in direction to what we see in the Rockies so this reverse faults are moving the hanging wrong moves now to the west relative to the footwall whereas in the Rockies the hanging wall is moving to the east why are they there well we think what happened was that the configuration of the subduction system changed so much that the stress started to fracture started to form these reverse Falls way inland way inboard away from the subduction zone but underneath the mantle underneath general changed its behavior it changed its strength and so much that was started to break pieces off and so really what you should think about the CDs are thrust slope small thrust fronts that is it here and goes run again here there are bringing these rocks up and they move in these rods relatively in this in this direction over here that still means that relatively we're moving North America and it's overriding the subtraction system but it's it's one of those amazing features the wind reverse classic area but you're of course familiar with the Black Hills and said that's what the monuments are pre camión is the easy key rock there we do not bring up a lot of Precambrian rocks that way all through the country but in that part of the world we do it tells us something about the deeper connection between the mantle the subduction system and the crust as it exposed so basement uplifts is a good term for them as long as you realize these are on reverse falls these are not these are not a vertical fault these are steep reverse Falls they're not terribly steep sort of 30 degrees or so but they bring these these rocks up the geologists in the area will call that Laramide deformation that's the term that you often hear Larimar style deformation descriptive term for that simply being base more basement uplifts over resource falls that's what that really means as a term so that's the word lera my it's it's a geometric name although sometimes misused as a time name as well there's no Laramide time to learn my style the deformation all right IV then they move on a little bit of area over here I'm going to start to to move on we're looking that's part of the world we start to see that there's a younger feature that over prints all this history that sort of starts at the end of this full thrust belt formation and these these Laramide basement court uplifts you start to see that the western US starts to break apart we actually extending the western US we start to see that there's this talk called basin and range extension all these areas whereby we have highs and lows and highs and lows that we looked at these these geometries and so we find is that over printing this history in the younger part nah machine learning the messes in the Cenozoic so when our starting summer in the Maya scene in particular but starting in in the in the Cenozoic middle of the Cenozoic you start to see that North America at least that part of North America not the other part but the part is also south of what a subduction still takes place so it's in the part where we are away from modern subduction we see an area extending again why is it extending it's an unusual feature it's a lot of talk about it in the US because it's in the US and a lot of people work on it and everybody has gone to these areas and everybody does that research unit we've had a great day in dating project in that in that area but so it is it is quite unusual and again it probably reflects the fact that there is an interaction between the plate subduction that took place and the upper part of the Luthor sphere making for this unusual regional extension effects that's that is called the basin and range extension there are no other places in the world today that show this kind of geology even the extension in the Arabian Peninsula that we talked about which is the open the Red Sea that is not so widespread this is a very large extension and continues today it's the source of some of the reasons earthquakes the rich crust earthquake that took place was a pair two earthquakes one earthquake was this Basin and Range that extension and the other earthquake reflected the San Andreas Fault that we'll talk about in the next two slides as we move forward but just to refresh your memory of the geology of these of these things this is what these metamorphic core complexes were about we talked about regional extension we talked about continental extension this is the area where we had these low annual normal Falls it's extension so it's normal faulting and we even found in places that we brought up these the the deeper underlying geology because as you start to remove the top you start to by isostatic rebound you start to bring up the the deeper party you find these places that the deformed rocks and the rocks that are at greater depth sometimes the pre camión are being brought to the surface metamorphic or complex was to turn the people corns before they understood them so now we understand how they work so that's why that area he sits in so that's the younger history that's the Cenozoic history of continental extension it takes place in southwestern us we do not see that as we go north in the US we see it a little bit there's some faint pieces left in the the most northern part of the Rockies but I should go into Canada it's essentially it's a few places maybe but essentially we don't find that so it is really a localized effect reflecting the the type of subduction that takes place with time it's not enough to explain all the details but there is always this interaction between the plate going down and the overlying part and in this case it came to the structure all right now one more feature that we talked about I play the animation it's a tiny Atwater's animation that's the fact that we have some additional things is that as we have the subduction going on we were eating up the rich and we eating up the rich which connecters the transform fault and so the san andreas fault system is the representation of the fact that we're steadily eating up the rich that separated the one the up late Farallon plate it's cold here sorry it's wonderful could play down the know of the part yeah but the Farallon plate was used to be very large and the pacific place but north america is moving over its own rich system over that rich system and as it does so the connectors between the rich segments are now on lands there underneath california and they still connect downwards from the gulf of california up to justice or sort of oregon and that's what the san andreas follow this that's the youngest part history extension still continues but now we added about 20 million years ago history of the san andreas fault evolution very unique you can now start to see how complicated the geology is at that part of the world a lot of these features let's go with that okay we talked about all these things that's the context i want to place them in i just put this map up to give you a flavor and a bit of a shout out it's fun to go to the to the UNESCO site you can actually we nowadays with GPS we have real time real time meaning we can actually measure the displacements and they on the order of centimeters a year which is what the characteristic feature is but along the San Andreas Fault they're on the order of five centimeters a year the length of these arrows is the amount of displacement on a yearly basis and so this shows not only the amount of displacement but also their relative displacement based on a geostationary reference frame that of course is in the sky that's that we look at so remarkable nice coherence in those features its dominated as you can see by the San Andreas Fault in North America the long north northwest to southeast the lines are the San Andreas system but if you dig it a little bit deeper and look at these area errors over here that's the memory of the extension that still continues today as well hence the Ridgecrest one of the reasons it takes four so it's fun to go there and have a look at that and we have we have instrumented the country unbelievably so we can have these real-time measurements as we go forward okay let's go to a new segment let me slide my own slides forward so I know where I am in my slide system there we go so let's have a look at it's a that's another part this map again it's trying to get you to word to get you the flavor of what we gonna jump for so we're gonna go now and look at the eastern side of the country the Appalachians that's the name that we that we give that mountain belt it's a mountain belt that is Paleozoic in age now what that mountain build represents is an other part of the history in history before the Cordillera were there there were no Cordillera mountains and this history took place it's a it's an very interesting mountain belt obviously because we live near by it but it's also the first mountain belt where we applied modern plate tectonics to understand ancient tectonics it's the first place where people who are able to start to use the tools that you had learned in the class so far that we talked about the tools that the identifiable features accretionary wedge is a few lights arcs all these features that are characteristic of modern plate tectonics people applied that to this old mountain belt but there's nothing active anymore and they found all these features they found the old trench phil deposits they found the accretionary wedge they found the island arc system all that long quiet geologically not active anymore but they were preserved so it's it's really revolutionized plate tectonics in the sense of not only understanding that thinks today but i said you can apply this now to all systems and see whether the modern observation of tectonics holes in the past and it turned out it holds extremely well plate tectonics works for a long time in the same way on our planet and so that's what this these write-ups are as we go forward now let's so come it's again to get your your bearings we move down into this window is the Paleozoic window of the paintings the eraser does not work this thing I think no does oh oh it does turn it over we're gonna look at the Paleozoic part of the history it also we've looked at the Appalachians because that's where we found the best evidence for fossils that help us understand the explosion of life that's really what this started much of this thinking and in the UK whales in particular it's a beautiful sequence of the lowest part of the patty it's all red with a lot of fossils and we learn a lot so we're looking at the history that goes back to the beginning of the Paleozoic but this picture up to remind you of something that all that we have is evidence that is no longer related to ocean floors we have know the ocean floors that we see today have a memory of their evolution via the ocean floor stripes you learned up in the intro class but the ocean that we talked about here the separation of the colonies oceans are long gone they no longer exist so how do you be no difference well this is what a fossil record comes in the fossil record told us that there are places where there were continental margin systems where animals were living but they did but they did not communicate it was too far apart apparently for some critters like like for example trilobite to get their way from one site one continent to the other to another continent gotta see my own hands they don't actually there's interesting you don't see Hansel you move them so they using fossils to understand the separation off of continental blocks and these fossils the classic ones of course have brought it in an example are a trilobite because they were the first to really puzzle as it was puzzled us was that there were tryna bites that you find up in in in in Newfoundland and you find him up in in in in New England on the most most ocean side we found this this this trilobite that look like nothing of the other trial of us that we finally came in rocks in North America and actually both of people so much that the boat their trial about paradox IDs from paradox why is it there and it was not result for a very very long time until people started to realize that wait a second we find the same trilobite also at the African side of of of today's plate configuration meaning that it looks like that trial by it was living on North America side and on the African side and of course what we figured out that plate tectonics which is what made this these arguments are powerful told is that of course their configuration were very different North America and Africa right earlier were fully in contact to one another in in in in in the in the Pangaea configuration but in the cambrian times they were widely apart and so we find fossils here that are different from fossils that are are here we found that other blocks in between hats the same feature so we could start to use fossils to understand the separation but also when things were close enough to have communications another technique that which really revolutionized the plate tectonics is paleo magnetism whereby we use the magnetic fields the memory of the Earth's magnetic field in rocks to understand their location that really was in the late 50s the first time that applied the early 60s that was a complete new line of science that helped us understand geometry because the rocks told us where they were at a certain time and they told us that they were not where they are today and so fossils at Bailey magnetism are the tools to do the paleo geography to make these maps that we we showed in many of the animations but we have no ocean floor magnetic anomalies there are no ocean floor in place preserved and so all this is based on that part of the history I'm gonna do the Appalachians a little bit quicker I'm actually I don't know how that's quicker or not but I want to do sort of can see the same sense if you look at these mountain belts here's a general map of the Appalachians we start to see the same idea recede what we call the North American part of it which is the stuff closest to where we live as I said that is the the all part of North America is it recognized in the deposits that we call the North American realm people call it Laurentia that's the term that they use but it's it's the North American realm and then the other thing that we find is that if you go to do place like Rhode Island and Nova Scotia and and and Newfoundland so different lands over here Nova Scotia region and in part of New England we find elements that are what we call very much look like they are Africa like they look like also rocks that we find and fall so we find in Africa they are the term for that is Gondwana that's a term for Africa people use for that but they're they come to on and realm we call that that's the fossiliferous realm and then what beautifully is preserved there's this orange in this green color in there those are various remnants of the ocean in between and terrains that are in between blocks that were on the ocean that was now long gone that are just still preserved because they were not subduct about their arc terrains their entire volcanic arcs that could not be subducted they can weld it on to the margins as that ocean that existed before the the Atlantic the proto Atlantic Ocean you call that Iapetus is the term that's that the specialists they are useful at ocean they call it the abalones ocean but they show the remnants that are in between that are just all kinds of features plateaus oceanic plateaus oceanic islands arc systems smaller sub continents that are found and it fits exactly the story again that the Cordillera is in these are terrains that were retreated in this case not very oblique because they're not sliced up there usually terrains that have their own internal part they're not terribly sliced up at least and you have this configuration of one margin the North American margin one side another margin on the other side and remember of it and the stuff in between is just the remnants of the ocean basin and all the way from Alabama in the southern part to Newfoundland we can see that that geology there it's a it's a remarkably well-preserved and continuous sequence in part because it doesn't have that huge obliquity but it's a little bit more complicated we're seeing a little bit in the southern Appalachians and but that's the general setting of the Appalachian of the Appalachian origin that a cool thing here is that talked about the fact that these are oceanic realms these are features for oceans that are preserved but what is the cool thing is that we actually find evidence we find rocks that are preserved that tell us that the worst wants an oceanic sequence in between there was once rocks that represent the ocean the ocean lithosphere and right over here where the arrow is in this part right over here grow grows more in Park in Newfoundland if you go there it's very strange it's sorry I can't show you samples I have the samples but the rocks there are have this is rusty well basically they're very not pretty they're oddly the rust rusted rocks what they are these are iron rich mantle rocks that of course as they got exhumed they reacted I reacted with oxygen and and rust it it's just a rust lookin feature but that's the lower part lowest part of the of the oceanic lithosphere sequence they had remember it had the salts at the top it has seeded dikes it had cab rows and then it had ultra matrix peridotite here this is the picture of the brita type part of that sequence where we have these rocks preserved of the Elissa sphere of the lowest part now why is this so interesting this is lower or division this is 480 million years old this is ocean floor that this of course is no longer there but in a few place in the ocean floor got pushed in it orogenic system on the on the on the continental margin and therefore it got preserved they didn't get eroded off but it also actually did not get subducted it was just a small sliver that was pushed in we also find that same sliver like that in the english side in in the UK where it's called the colada nights and in less so in Scandinavia there's more high-grade rocks but then they discovered the exact same age and the same an excisional signature in in rocks in in in the UK site they's called Val and Tre it was the first place what it was well described so here we are a memory of oceans that are no longer present a few slivers of them are preserved these are the ophiolite sequences that we were after that we targeted to get a sense off he doesn't wants to tell us there are ancient oceans and this is a remarkable one because it just basically didn't get here either and it's just a lot of mental rock sitting by the service not pretty but we don't have a lot of mental Rock this is one of the places where we have a lot of them to walk it's not as well preserved in other places in the along the UH places but far the best place to see that there are also excellent pieces of anaglypta sphere preserved right up there and the other slivers that are preserved in there so it's it's quite a remarkable observation it allowed people to apply modern plate tectonics to the ancient times as we go to go forward so geology looking at rocks now we can actually put it in in context the question is why don't we have the same spectacular outcrops in in Northam in in the u.s. part of the Appalachian so we go to the year as part it's because as we go to the southern Appalachians so the part where my hands ride again to serve the party Appalachians there we find probably the same early history but it's completely overwhelmed by a very laid deformation cycle in the Appalachians that generated very large stress falls gigantic thrust faults that that put that shaft a major amount of the sequence on top of North America much more so even than the Rocky Mountains the displacements here or any norm and so I draw this line over here an enormous length hundreds of kilometers long of a thrust fault that took most of the southern Appalachians and moved it over the rocks underneath the shield rocks that are underneath and it gave the large large Appalachian a thrust system because that the regional Appalachian detachment and and so the rocks that were once there were overridden by this large amount of displacement we didn't seed it very well there were a few indications of that or a few indications were that people were working in some areas and they were actually looking at rocks and they found relatively high grade rocks that were overlying on metamorphose lime stones sort of not likely you don't have high-grade rocks that are older of lying younger rocks are lower grade so they assumed that they were already reverse falls there and that idea was already embedded for a long time they called a window remember the window that he rose into and and cuts through and someday the reverse fault system but it was not until we used seismic techniques when we use techniques that all companies are using to understand the deepest structure although in this case we were not looking at the fine granularity that all companies use but we're looking at the deeper structure people set up a system whereby they generated local earthquakes thumpers they use these trucks that were bumping up and down and they've dropped the truck it generates an energy wave the energy passes through the earth and there's there's recorders along along the way that that sense the pathway of these of these of these waves and in doing so they could see the deepest structure and they discovered this is large-scale detachment and that is remarkable because it is so different on the northern Appalachians but if you actually look into those blocks that have moved you'd find features that fit the northern Appalachians in this case however in the in the US side they are completely moved laterally in a in this case in a in a westerly like direction and what it was is that that is the point where the nose of africa bird over the bulk of africa pushed in against north america and simply that collision that premonitory has we called it at the time in our lectures is where a lot of this shortening took place whereas in the northern part yet nations there wasn't that much late Paleozoic this is old late pennies or Carboniferous in age as we go in d.c in these various features so very different geology in detail even though I first told you that the general outline is the same continental block continental block intervening ocean basins in this case that intervening ocean basis system has been shoved even more over the Laurentian continent making for for the challenging again it however it's quite easy to tease it apart to understand deposit Go Go with that what's this we no longer do this type of analysis it's incredibly expensive to do also have to have a lot of permission and stuff like that but it made it start to look at what's below the surface geology how far this serves geology extent down well in this case much to our pleasant surprise description of a structural geologist the service geology really was a thin veneer it turned out below that it was a completely different geology because we have these large-scale detachments that characterize that and if on the future and by the way I posted the the future I spent something I have time on my hands too because things are different for me different things Leah I'm posted our field trip and do it let me know what you think this is not high end this is not a clever beautiful amazingly feature feature Laden but I wanted to show you two stops I want to show you what you see it two stops and I gave you brief descriptions what we have it two stops but I may do a voiceover maybe not not that desperate to hear my voice all the time but look at the field trip all the features that you'd see there all the structural features are all Carboniferous features that are all that lake values or a deformation and wrinkle there everything in that area including the beautiful full structure that we find in in cycling hill this picture this giant sink line that we have we have to be sure up there those structures are not found as you go into New England they start to become very different and in going to Canada it's even less of those structures are preserved nice different way of looking at features however still the same terrains thrusts for the thrust belts all these features are there I'm gonna skip the ORAC line okay I could say of course take for ten minutes but there's more break for me than for you and they're so bare with me and as I just finish this off as we go to the third domain in the third realm in in North America and then we have all these things together and then you can can do some stuff if you have questions please start to write them down right and do it do anonymously if you preferring a name it doesn't matter but that way I know what I can answer I have the screen open here that shows the questions so I can sort of see as they come in and I can answer them a little bit later on you I will not open the your voice or your video we'll just do it all by typing it's a little less disruptive with 24 of you 25 or so online okay so we've looked at the western side the career inside we looked at the eastern side the Appalachian side so we'll look now at the big internal side with this reddish color and they said is bluish tone it over lies that the platform and also a bit of that slightly younger stuff over here although but notice my time on that that's the erosional material from the evolving Cordillera underneath that is also shields and so it's all platform type deposits and so that's the segment in there so so let's have a look at those those features I call it the Continental interior why was because it's the continent and it's the interior and here is the first thing that's so much fun most people to do plate tectonics only talk about plate boundaries they always talk about all the action is at the plate boundaries earthquakes volcanoes Falls yes that's true it turns out when you look in North America geology we found as a lot of geology preserved in the interior the geology is first of all the history of that interior itself how it is formed what one example of that the interior wasn't always an interior it wasn't always a single block so it has its own history of tectonics how it got formed but also we have learned that the interior the plate interior is not a completely rigid unda formal sequence it is heavily deformed as well plate tectonics concentrates the information at the plate Marie's but it has considerable defamation still in the played interior and some of that is highly debated today these are the unresolved issues today and I could go on great lengths there it's one of the areas that we've worked on for many years maybe another time another class but it's also the interior tells us that plates are not unbe formable the Marge's have most of the defamation but the plate interior also seems to show quite a bit of information in addition to its own evolution so there's list of things that we discuss are actually giving you examples for what happens in the in these plate interiors and all these things we touched on already in the class as well so again it puts it into context but I wanted you to get a flavor of where we are just to make sure that you know where we are either sitting on somewhere over here this area you also noticed I really enjoyed the mark-up that I can do it this hopefully makes it a little bit more alive and then just staring at the screen and see my head ball back and forth again the time frame well why this is really becomes prominent of course we're talking now about much of the history of the blade of the Continental interior is the history that is that Precambrian history there's a lot of stuff happening in in in the four billion years that we have left in that particular particular window my dog thinks I've talked a lot now he wants to get some attention and so we're gonna look a bit of that but not gonna look at the entire history there's a lot to say about it but I wanted to give you one flavor one example of a plate tectonics in the past did and also to highlight to you that it did about the same as it did now except that the rocks reserves are are different because we now are looking at the deeper part of the plate that is that's preserved erosion is taken off most of the top the other feature that's important it's trickier to work in the Precambrian because we no longer have the benefit of the fossil information there's no Shelley fossils that are after 600 million years before six million years should say we have no Shelley fossils that help us do any kind of domains where these critters were living and so we're left with only one tool which is paleo magnetism which is the position of the Continental relative to the polls as a tool to consider the location of the of the continents we and then we look up worthless ology similarities and times of deformations a pretty good story time constraints little logic constraints and paleomagnetism but we no longer have the fossil so as we go back in time in the Mesozoic and the Cenozoic we had ocean floor anomalies fossils and paly magnetism we go into the Paleozoic we only have fossils and paleomagnetism and if we now go into the became ring and we only have paly magnetism left and so our constraints are looser as we go back in time and that's why it was a little longer to get this this story figured out but it's the stories is pretty nice and consistent and just to give you a memory of displayed interiors I like this map I showed you a while ago and look at the terms over here the shield and the platform and you can see that many of the continents that we call the continents have this interior right North America much of Canada and only Neath the platform sequence the most of South America is an interior a plate interior sequence it's an old history that it's preserved Africa is all Precambrian in origin disty the ages the provinces in there Western Europe the Scandinavian sequence there these are all do many other parts there are premium Asia is an outlier in there only in some parts do we find all the part but much of the action that we talked about in the malleus actually is the interaction that's all Mesozoic in age but Australia is again good one it's nearly all Precambrian it there's a few younger belts on the margins in fact just like North America does in some ways Australia is the mirror image of of North America whereby in the Australia these younger belts are on the eastern side and in North America the younger belts are on the western side but Australia has a lot of history as well and so it gives you the flavor this is not a North American thing all the continents showed is history it just happened to have a lot of information because a lot of geologists work being around and the nice thing is in Canada there's a lot of relatively a lot of outcrop because vegetation it's pretty brutal up north and so vegetation is very thin and so we're able to get good outcrops but I wanted to focus on the u.s. purposely I wanted to sort of make sure that we get the it gets you a sense of the richness of the US as we talked about and so as we focus on the Precambrian rocks already I mentioned that there are these funny little Bluffs in there I just marked up in this case it states the Black Hills but these are these Laramide uplifts now they are young in their formation but the rocks that are brought out there are actually these pre Canyon rocks at the surface but really the last good outcrops of that much wider extent of outcrops in Canada is found up in this innocent in this Minnesota segment right up here yeah it's called the superior because the whole tectonic domain is called the superior province that's one of the names that we use for the pre-k me in there these are not time names these are geologic entities as we call these these features there but we do find that shield-like rocks which is so rampant in Canada we find some of that exposed up in in in in the US but much of the US the rest of the US if you look at this map right over here is all covered by this younger platform sequence so it's underneath we don't see it very well now one feature that will focus on me I mentioned before is it's a feature that sits somewhere over here which is a big part of the salts you've stainless 20 up to 20 kilometres thick basalts it is an example of rifting just like Africa as rifting today a billion years ago the North American continent was trying to rift in the same fashion it never worked out because it never broke up these two blocks they just ripped it but it never became an oceanic system it just remained a continental rifts and it got frozen in time but it's a gigantic one it shows that nature really tried and and a lot of lavas exhumed but it did not really succeed in generating the the Rif history will talk to that a second as well and then the last thing that we'll touch on just want to highlight that because that's our geology that's our back door I made these jokes and there's not much geology to look at a Michigan first of all that's not true and the Upper Peninsula we find Precambrian rocks right if you go to the U P we find the little pieces left of the rest of Canada has lots of but you find interesting pieces there iron deposits are there copper deposits that are so shielded with the midcontinent riffle touching those as well but our part of the Lower Peninsula is an amazingly weird feature the test is giant Basin nearly five kilometres depth at the epicenter I that represents right over here nearly five kilometres of sediments in the Paleozoic were filling up this sequence on top of the plate that means the plate must have been underwater obviously otherwise you won't have the deposition of an environment but at the same time that it's not everywhere five kilometres it's only there so those because I'm dimples I like to call dimples these are giant basins that are found we find that in Michigan is the best example Illinois has one as well but it's not as good we always still University of Illinois did the Michigan base it's a hole what does to know these things let's begin giving you the framework of these features what marks the history of understanding the the evolution of the plate interior and permit me one minute to to advance my slide so I can see the sequence of my slides as well my own there we go what marks the much of that understanding of plate tectonics in a precarious the realization that Pangaea the supercontinent and his Paleozoic an age limit is arranged is not a one-time event it's not a unique event we actually discovered as we looked around that it would seem that continental blocks had been organizing themselves into those be called supercontinents more than just in the independent gia times and so the Precambrian gave us insight because we have so many billions of years to look at we don't we're not limited to the 540 million years of the phanerozoic now we have four billion years to look at this that there were multiple of those of those supercontinents I'll show you one which is extremely well-defined now we're really that's a very well constraint because it was the first major target we might after that's called the Rodinia supercontinent there was a super confident probably in between Rodinia and Pangaea it's called Gondwana supercontinent it may have been not as complete a supercontinent but it doesn't matter it gives you the flavor that there was another configuration where the plates were together let me go back in time we find that we have a supercontinent that is sort of at the at the early early pressure or zoic and it's called nude about some columbia routers and even people have argued it gets thinner the arguments the evidence gets thinner the evident gets Sophina starts to look on those british crime shows are by the smallest piece of hair there's a whole story to solve the crime we have even evidence it may be at the the at the Archaean there was an RT into per continent the data I'm not gonna debate it here it gets already thin not because a geology is not good there's not a lot of geology there's not a lot of those old rocks that are preserved but the key thing is what the understanding the Precambrian geology made us realize that that these super continents are a features that are persistent and they're found multiple times and therefore you can make the fun game that the future will also have a supercontinent I showed you one another one example and that's Chris Cortese and I put together Chris wants to call it Pangaea próxima but you could argue that as opposed to to closing the Atlantic you actually closed the Pacific Ocean and some others have done that and if you join America and Asia and remember Georgie or funny people if you combine America and Asia you close the Pacific Ocean in between you get a new super cool super bouncer and that is called wait for it mazey indeed very good who knows it but we expect more supercontinents in the future as well I like amazing more as a name but I think the concept of closing the Atlantic is more likely for a number of geotech tonic reasons that won't get into now but we expect more help ng alike reconstruction 250 million years from now I will know for sure and I know who was the right and so by that time I'll let you know but what the answer was I think what happens is that I am still on the other screen so let me get to my own screen so one piece of evidence was we looked at mountain belts around the world and people found out that there were the same age mountain belts over many many many continents around they were just like the Cordillera but not as not as this young service deposits they were a bit like the Appalachians although the younger deposits were not there but there was this again is narrow belt of an organic system but in this case these belts were made up of older rocks obviously cuz when it became but particular also higher metamorphic rates we're looking at the deeper part of the lithosphere that the stuff that it got exhumed to the surface today with all the cover sequence got eroded off but if you start to do that you could see belts of about the same age about 1.1 1.2 billion years of all around many of these create an equation of these of these continental interiors today it's not at the margin I'll show you where it is today in North America in a second actually I can show you that quite quite obviously on the map over here we're looking at this connection right up here this far beyond North America now what are the blocks are so North America is on its site so so turn you head over a little bit you can see that Greenland is marked up there and that's North America Lorentz yes we call that and this thing called Amazonia what that means that is actually South American site to the east of the Andes Mountains the Amazon system the Amazon eco system is built on this blocker Precambrian rocks and so this is a part of South America that was in this configuration as the same orogenic systems we worked in these areas we have got the same geology in Amazonia as we found up in Ontario and we realized of course that these belts are it's very similar because they were as we did in this diagram they were connected in a in a supercontinent configuration when these origins were formed wherever the origin was formed when the two blocks were hitting and so this is what this was and so this said this road in iya supercontinent the modern of all confidence is is the is based on the fact that we found these because Grenville orogeny type and Grenville is not an H is a descriptor of an Origin that we find in in in in North America and I found all these belts in there the diagram on the left is a little bit better it just simply shows you the in this light lighter color right over here this is G on 10 - 11 means it's around 1.1 billion years old and you can see that you can put these blocks and organize them and so that they have just like Pangaea dusted in a younger history and had this configuration where these belts are connected to one another and that sort of made us start to use the power of dating and the power of little logic recognition of course these are all metamorphic rocks now you no longer see arcs or stuff like that you see ma'am our first arc systems and like we can make this configuration so this is the map of the the supercontinent that is the the best constraint as we go far back into the into the into the into the became Ian because as we get older we have fewer fewer rocks it's harder to put it together but stay there our Denia supercontinent and why this is fun for us to pick this out to emphasize this in particular not they don't want a supercontinent is that how we use the map of North America and what we actually recognize is where it is belt that we call this this Grandville belt and remember sitting remember we are michigan right over here right over here and this whole area right over here this this segment over here and it goes into the direction in that direction that is actually the front of that old orogenic system that Grenville orogeny system that was marking the the collisional boundary between the en bloc on this side and the Laurentian block on that side marking that collision of that and made a mountain belt and why is that amazing is well first of all that's explained all the geology we have in Canada but also we're sitting right up here as you can see and we were sitting a billion 1.1 billion years ago exactly where we have the front of the mountain range what I always tell people that if you would go back 1.1 billion years and I have asked my physics friends to help me get this going you would find Himalayan type mountain range sitting where an arborist today look outside my window little of that is preserved but actually there were mountain ranges that were as big as the emolia's and we know that because the crust today is still 40 kilometres thick it's orogenic crust the metamorphosed metamoris and tells us were about eroded down 40 kilometres so we're missing 40 kilometres of top sequence and so these were mountains just as told and the crust was 80 kilometres thick which is what it is today I'm gonna Himalayas so a mountain belt that he runs all the way through she can sort of continue this on in the into into the end into the southeast it gets harder in the southeast because it's chopped up a much younger history as it had sliced up and so but it's really beautifully defined in the in the north in the north eastern part of North America it did a lot of work over the years in that that orogenic systems but change your mind the Appalachians were not there this white area that is on this map is widest area right over here plays right today that wasn't there that's all much younger history and the Cordillera of course right out here wasn't there either it's also much younger history so you look at a different very different shape of that on that continent some geology because it's fun it's nearby it's worth a field trip if you ever get the time you can just drive up you go up to get into Canada got the Kings Highway and you start to go to go to separate don't go to Toronto go to Sudbury direction you would find that most of the outcrops along your way are these brownish grey rocks that make up the Grenville Grenville nicest as we call them it's a nice because there's no not many system and a morphic radius and fib alight or sometimes higher so you don't have a lot of micaceous materials anymore so then the foliated rockets old affirmation rocks becomes a nice looking rock but as you can see there are lots of faults in there there's a lot of deformation in there this is the contact where we find the boundary between the origin called the Grenville origin and I should go into Sudbury and the road you see up here if you keep going up in this dis road you get 2 sub 3 actually this high grade Rock sitting right on top if you go back a little bit to it along that road right on top these low grade rocks that are older they are a southern province rocks but they are unmet amorphous essentially hardly Metamorpho sediments and he's very hard works it's sitting on top of that that is a major detention structure as well so the Grenville is just like the southern Appalachians it's a major detachment structure that push these high grade rocks on top of the margin of then North America then Lorenza it's a little complicated to build up but I want you to see those similarities it's just an older orogenic system just like the Appalachians except we don't preserve the Appalachian type rocks anymore it's all you wrote it up we just see the deeper part of these rocks so there's high grade rocks of the black rocks sitting on top of low-grade rocks that tells you it's the wrong configuration that's what a thrust boundary is it's called the Grenville's front that's the determine there why I have decided here that we are so close to the type locality of that I've showed you over the time we talked about my nanites and stuff like that he's high-grade metamorphic rocks many of those samples came from from the ground floor because it's just a spectacularly expose origin but if you go there and you don't have the context it looks like well it's just a bunch of noises you know used to be called the sea of nice for that reason and so the other feature that's very characteristic was this belt right up here I'm gonna go a little quicker because I see my time is running out I have five more minutes technically but please permit me to take a few more minutes he can always stop this Molly you can't stop it now but I'll post the tape but the midcontinent rift which we talked about is the attempts of the continents to strive to break up and that a lot of basalt but also why is it fun for us it is the source of Michigan's early wealth the copper of Michigan which make Michigan a very very rich early state was because of the copper that was found in these basalt in these in these Mid Continent rift basalts that were also collecting erosional material so they're sand stones in there and so hence these are conglomerates and these are coarse sand stones and they also concentrated the copper in there this is what we got our wealth from the failure of the Mid Continent rift deposited first the basalts and the erosional products of that and that's where we got much of our wealth from the rift never made it did succeed 1 million year old rift it tried but it didn't work out but it left us with the wealth of the copper that's a is their cup of harbor is named after the copper that's the copper conglomerates there and that we find there and if you go to portage lake you find love us just like basaltic lavas those are these these are the rocks that are the basalts that are associated with the rifting which she founded origin lastly and I have too much less left just just to get you returning back to the flavor he's the map of Michigan where I'll always make this garment day long not much to see a machine a bunch of gravels that's true the surface is really not all terribly well interesting for in structural geology but if you would start to go a little deeper or if you go to where everybody who seems to want to have a cottage in Michigan you go to the northern part of the Lower Peninsula you actually have start to see some outcrops at the bridge we see their lime stones are popping up the lower I'll pay a certain lime stones are popping up at the bridge but it turns out that the entire substructure of the state of Michigan is this large nearly perfectly spherical sequence of rocks meaning they are a basin which is filled up and not a part of the basin filled up in other part the basin filled up another part of the basin filled up with the deepest part of the basin nearly 5 kilometres starting at the base of the Paleozoic and the youngest rocks in that sequence our upper Paleozoic sore about we have about a from about 540 till about 300 or so million years for 250 million years of deposition the plate is not quietly sitting there it only happens in this part it's not all over the plate it's not the rest as you wrote it off only this Michigan part up there and so we call these things intra crate onyx basins nations because they are depositional environments restricted depositional environments in track Ratanak because the kraton is that undeformed ball is this strong part of the plate not to plate boundary but it's in the middle of the plate so it's in inside the plate inside the crater on intra create onyx its paleo sorry because of the age of that particular feature there's also it's not the only one they don't know it also has the basin in there and in between our high areas arches so we have highs and lows and highs and loves the plate seems to be pretty deformed actually for a undeformed will plate interior there's a lot of giorgia that's the beauty of of eastern US geology it's not boring at all it actually tells us plate tectonics is not done when it comes to plate interiors well plate boundaries there's also played in theory history in the last map that I'll show you is this map that I showed in some incarnation I think earlier on I can't remember our detail it was but it shows you this crazy on the right is the the US only the US side and shows all these features and all these features are deformation features that are happening after this plate was formed in its current configuration so after we generated the interior part of the plate no plate boundaries there anymore we still see a lot of the information already mentioned the the midcontinent rift well that's a pretty big cut there that's a big big fault system 20 kilometer basalts was deposited there so you mean you you're cutting half the the the crust in there we have these big basin sitting out there they played this generating basins we find other bays and sequences real food rift in places like that we find later a Precambrian basis in there ll through also you find fault systems false that are offsetting things we find in some places significant fault displacements inside the plate even yet we even have as you know places where we find modern earthquakes the New Madrid system in in in in our in interior in the plate no plate boundary nearby the only plate boundaries are old there's nothing new in there and yet the plate is deforming so the deformable plate is actually a feature that doesn't get a lot of attention because most of the plate tectonics is action today it takes place at plate boundaries but every now and then giant earthquake that happened also in the plate interiors and this is what actually is a hazard argument we worry about said they may not be as common but it's all the more risk when they do take place but the whole history of the plate has been one that after it was formed as a consolidated strong rigid plate interior deformations still continues on and some of us have started to work on thinking about how is it possible to get all these features well it turns out this is why it's nice you can actually link events that are happening on the on the appellation margin with features that happening on the eastern side of Northam you can find features that happen under Corday year and margin the things that happen to the code here margin with feature of defamation that happen on the western side of the plate interior so what we're seeing and we call that stress transmission we're seeing that plate boundaries are obviously where the action is but the stresses of this plate boundaries are able to go inside these chronic blocks and still create all kinds of features and sometimes dramatic features that are still a reflection of plate tectonics but whereas plate tectonics at the margins is horizontal here much of this stuff is vertical so if you want to simplify it young interior tectonics is wanted more of vertical tectonics but still it's linked with events that are with plate tectonics far away so far fields tectonics as we see as we like to call that and so if you now wrap this up 11:22 so I'm I have a couple of minutes over but go back to this map now when you look at that I hope and now there's a lot of information you may have to replace on segments here but I wanted you to look at this map and start to see like what do I tell people about this well there's a lot of richness there they're all origins young origins ancient origins the Granville that I didn't mark up would be right up here that's the Granville boundary right up there should put the Chi in there so or ancient or nolo it looks like an origin that's why I don't mark it as an origin but it's an ancient origin in there and the origins also in the in the in the southwest but you start to see now how you make this content and North America is remarkably nice obviously because we live here but also it has preserved much of that history other continents either don't show much in the younger history like Africa never much of the old history only Australia is a bit like that but Australia doesn't have the beauty with North America has record here on one side and Appalachians on the other side so North American continent has been there the deep playing ground to really understand tectonics and it's not surprising therefore that plate tectonics today is understood everywhere really found its roots and its acceptance in North America when things made sense to look forward to

Channel: Ben van der Pluijm UM

Views: 10,810

Rating: 4.8793101 out of 5

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Id: RObBct7_5Ec

Length: 79min 19sec (4759 seconds)

Published: Tue Apr 21 2020