UTIG Discussion Hour: Nicholas Montiel, UTIG

this talk I had first so start at the beginning so so something interest SE something you part um it's not just so you looking in the and us is that we can start in New Prett looking at this section and SE okay um we're have to mute that okay how does this sound for everyone online you might have to turn up your volume yeah I have my volume turned up um okay much better okay sweet okay sorry for that all right thank you for bearing with me all right anyways what was I saying uh yeah so you get these Continental Detachment vaults that dip towards the ocean um that start to exume this uh subcontinental mantle down here so you can see where the fault comes through here um and this so you know there's a full area there's multiple lines coming across it and then there's a transition zone where these Faults Are become overprinted by Detachment faults with the opposite versions dipping towards the land um and that these Detachment faults have this very distinctive sigmoidal you know anastomosing structure and these are happening in the uh uh and these are occurring in the upper mantle and between these two systems of faults you are Exum uh uh um the upper the lithospheric mantle up to the surface and as you move across it's especially visible here but as you move across what ends up happening is is that sdrs which start out very thin get thicker and thicker and thicker and thicker then in the foot walls of these uh high temperature Shear zones you start forming layered oceanic crust um just through an increase in intrusion um so it's really interesting because then you get finally get to see some of the structures in the mantle that are controlling deformation As you move across the rift dri transition as you transition into true oceanic crust so um so that was what was seen in the Ivory Coast um we also wanted to uh see what processes control that transition uh through numerical modeling um because that gives us a view of the process not just single snapshots so crust lithospheric mantle asthenosphere the red is uh these high temperature Detachment faults that occur through damage rology uh Dynamic grain Rec crystallization uh the uh green are the normal you know attachment faults that are happening in the crust uh this glowing purple to yellow spot that is where you're going to have magnetism and that magnetism is eventually going to start underplating as yellow dots here and the boundary conditions here we have a constant extension rate um that we get to prescribe at the beginning um and uh eventually you form these you know anastomosing Detachment structures you get these domes of mantle and eventually uh the model you know cease we turn the model off and it becomes starts to become unrealistic um because we don't have a lot of volcanism we're not actually modeling the dying process so as soon as we start getting these you know symmetric you know uh flipping um you know core complex looking stuff that looks a lot like a uh um ultrasoft spreading Center like the southwest Indian Ridge or the G Ridge we say okay cool this is where um this is where oceanic spreading has started and now we can look at the structures and see how realistic this actually is turns out pretty close um this is one of Z was one of many different models that we ran um but here it is in uh kind of zoomed in this is that same line from before uh and then here it is matched to the uh to the model and the important thing here are looking for these homologies these structural and temporal similarities between the two because process-wise they're very different one's the real world one's a model so you know but you know these uh structural and temporal and spatial relationships uh are really important and what you get are the same um uh L sorry oceanward dipping Detachment faults through the continent uh this doming of the mantle where these two Detachment fall systems intersect and then you have increasing magnetism and a more symmetric uh um high temperature Detachment fault system as you move out towards the oceanic crust so that's really really exciting and then when you put this into the greater context of how we think that these systems evolve um you can actually start to identify like so the Ivory Coast profile covers the whole thing um you know at relatively shallow depths stuff like Lon which I talked about earlier would be a more narrow part but it's down deep um at the very bottom of what you can see in the in the seismic um and then other places around the world like nurali and the Ural Mountains in Russia and the air plot and Ops also in the uh Italian Alps um these would show upsection portions of this uh of this um framework for Magnum rifting um and that frame in so that frame work begins with this idea of okay at first you know you have these um uh stresses that are you know everything's gravitationally collapsing you have upwelling as a result that causes decompression melting um that these two systems of faults initially are separate and then couple later on and then as they couple they go from asymmetric to symmetric and as this process moves forward and you start creating oceanic crust the presence of melt pushing Up From Below because it's hot and buoyant and it wants to push up from below you're going from gravitational collapse more towards you know kind of like this Dynamic uplift um which isn't a new idea poak and buck came up with this you know around the turn of Millennium with the idea of you initially have this top down you know collapse of the rift and then as you transition into sea floor spreading it starts to kind of run itself as this decompression melting apply stress from below and kind of bringing this back all the way to the uh you know to the question at the beginning of like how does this process happen if you look at the forces right because we have a prescribed extension rate um we're not applying a stress we're applying a velocity um so the force required to maintain that velocity and actually break apart uh the lithosphere as a function of time in the model right compare so that's this line and then compare that to what you would get from just like you know like classical Ridge push um and what you get is that during the early stages you need some extra force in order to actually break apart and start that Continental rifting process but once it gets going it can propagate itself um and you know that means that it could propagate along you know if you already have a rifted area it could propagate along the rift tip to adjacent areas um what that means is is that okay so for superc condent fation you need an initial push and if you look at the order of events for like the breakup of gondwana land for instance they don't start at the middle they start at the edges with trench roll back and then that you know back Arc extension actually propagates upwards and into other oceans um so this is kind of the uh the direction that this research was pointing that you actually it's you know not farfield stresses affecting the interior of the continent but you break the Contin at the end and then you propagate inwards maybe following weak zones like or origin or mantle plumes um which is in line with a lot of these ideas from like Calo in the 9s about you know risk propagating CS plumes instead of starting at plumes and propagating away so that's what we were at here and then um again kind of getting into the second part explaining the sudden shift into taking these same models and the same idea of thinking and applying them to a completely different planet well that started because one day Luke walks into my office throws this paper down on my desk and goes hey hey hey look at this you know you have these sigmoidal blocks and these really complicated you know fault structures it looks a lot like you know uh you know this high temperature Detachment you know faulting that we've been talking about uh you know for the mantle but here it's happening on the surface of Venus which makes sense the surface of Venus is 470 degrees C um so you you know your brittle duct transition is going to be pretty dang shallow and you're going to have low grade metamorphism up near the surface I was like oh this is really interesting maybe we should start playing around with these models because it looks a lot like what we see at like lzo and the ivorian margin and I didn't realize the rabbit hole that that would send me down it completely changed the direction of what my PhD project ended up being and kind of changed the whole course of my career because before I was thinking oh I'm going to do super content break and look at Rift and margins and the history of play tectonics on Earth and now I'm applying to places to to you know kind of pursue work and like okay what are venusian geodynamics like where did Earth and Venus diverge and all these other things so I'm going to back up a little bit and talk about kind of like setting up the problem of why these two things are related and why I think this is really interesting turns out Earth and Venus are perfect points of comparison with each other they are of very similar size uh I think uh Earth I think Venus is 93% of uh Earth's mass so they're very similar surface gravity very similar bulk composition um there have been Institute measurements through x-ray x-ray spectrometry of the surface and they come back looking exactly like more basalts at least at the four places where we have data points from um so they look a lot like mors and they're also formed in similar parts of the solar system there's a great uh thought experiment like if you were an alien on the alpha centuri solar system and you had this brand new telescope the wayes Space Telescope and you pointed it at Earth and you started looking at the mass the uh the composition of the atmosphere and you started looking at um you know the solar constant they' look Earth and Venus would look pretty similar to each other they both count as far as like planetary star numbers are as being earthlike and potentially habitable they're obviously not though um Venus has no oceans it's got this runaway greenhouse effect it's got this enormous atmosphere spere where it's like something like 92 atmospheres at the surface it's got no play tectonics it's got no internal magnetic field and it's got no signs of life as far as anyone can tell Earth is the opposite in a basically every single respect um and that is really interesting because why did they diverge how did when did they diverge and what kind of activity does Venus have and what does that tell us about like you know theoretical Frameworks for just how do planets evolve um so here are here's topography and bietry for Earth here's the topography for Venus they are very very very different but Venus also doesn't necessarily look like Mars or the moon covered in craters it's fairly well complicated and it's kind of an open question about what is going on there um you look at the hypsometry right you get the classical bodal Distribution on Earth that represents the continental and uh Oceanic uh composition that doesn't exist on Venus so as in bulk you know Venus seems to have a uniformly Basalt composition maybe there's some Regional variation but it we honestly don't really know um but it's clearly not play tectonics you look at the cratering record as like a proxy for the age of the surface the more craters that you have the older the surface should be kind of vastly oversimplifying it but because the size of the crater matters as well um here one of these six panels is actually Venus the other five panels is a random distribution of dots um the surface of Venus is pretty indistinguishable from a random distribution here it is for it's this one by the way here's this is you know the actual distribution this means that either and because there's only 900 craters on the surface there's only a couple options maybe the whole surface is a Uniform age maybe it's being resurfaced randomly uh and or maybe it just represents an average age of the surface and there are some regions that are younger but they're pretty small and localized there's a lot of room for interpretation about what kind of activity and how old the surface of Venus really is also we know also the rology of that you know lithosphere that is also important for determining how tectonics manifests is also you know not very well Quantified um here's an example of like a pyite you know and water um uh composition or sorry uh temperature geotherm for the Earth for the continents and for the oceans and then here's three different options for Venus uh and depending on the heat flow you pick and depend on also this depends on like how much CO2 there is how thick the crust is and uh also you know how much like how dehydrated uh the how dehydrated the crust and mantle are you can produce wildly different uh tectonics uh on Venus so this is the rabbit hole that I fell down was like okay so what is the tectonic style like is a stagnant lid you know is it this episodic that switches between being completely stagnant to suddenly all subducting in only a few million years and then you know the whole cycle starts over again or is it some completely different concept um like people have proposed ideas like plutonic squishy lid deformable lid globally fragmented flake tectonics plateless tectonics you know there's a whole family kind of exotic geodynamic regimes that people have proposed to explain um you know Venus's uh geology and geophysics and this is an area of active research so kind of bringing this back to Earth a little bit one of the key features of plate tectonics on Earth is the mid ocean ridge uh outlined in red here it's this globe girdling single extensional environment that is more or less continuous it's the youngest feature on Earth it's form in Basalt crust and that's where you're generating new material that's what's dominating the resurfacing on Venus and then all this stuff gets transported laterally until it is uh subducted away uh into the mantle thousands of kilometers away Venus has something similar yet very different it has This Global Rift Network that is also glow girdling it's also an extensional environment it is also the youngest future and Venus with a really important asterisk and I'll get to that um it also forms an entirely Basalt crust however just by looking at this you could tell it is not continuous uh it's a bunch of subparallel sinuous segments that are all more or less link to each other uh and also they seem to link these topographic highs um and these other like larger features um so like the driving force seems to be a bit different and also there's no obious place where this could be subducting um so if you are generating new crust here then it's got to be balanced out somewhere but we don't know where and we don't know how if this is where new crust is being generated so that was the question that I really wanted to answer was like okay if you try to do a mid ocean ridge on Venus would it end up just looking like you know this Global Rift Network or is that not a good analogy at all um and so that also brings the question of like where is new trust being generated and also really importantly if it is being generated there where is it being recycled to so kind of zoom in a little bit on one of these riff segments or some of these riff segments there's two features that I really want to bring up riffs and Venus are often called kasata planetary science has its own nomenclature for um naming features um but kasata for our Tes of purposes are basically just Rifts um they are pretty complicated um but they more more or less they don't really look like mid ocean ridges they look a lot more like Continental Rifts on Earth um and they also seem to link these large volcanic regions um such as like they call it the bat region for beta atla famus um but it's that's that big triangle region on the previous page um also these areas such as Aphrodite Tera and these absolutely massive circular features that are emis and kedl Corone um and speaking of the coron coron are these morphological features on Venus that are very poorly defined I think the official definition is any tectonomagmatic structure that is circular that isn't a crater I think is the uh is the more or less what the working definition ends up being but they can be very small they could be medium they could be absolutely massive like this one is atah hensic that's a good thousand kilm across the Artemis and ketopet lot can get up to 2,500 across uh across their widest point so there's a huge variation in size there's a lot of variation in morphology as well we also know that at these uh Pata in that these coron are often associated with or even embedded within um that the heat flow estimat are consistent with modern day activity now the air bars in this are huge because they're derived from models of the elastic thickness but they're about like 110 millatt per met squ plus or minus 80 so there's a lot of room but it is consistent with the c like there's some level of activity that could be happening at these features um they're also the youngest features in the surface in the sense that the aor bars on their age is larger than the than the estimated absolute age um so again like there's you know there's a lot of uncertainty but they seem to be younger than most of what's on the surface of Venus they also similar to Continental wrists have pretty low degrees of extension they're not like mid ocean ridges where you have you know thousands of Kil or miles of extension you know as you open up this ocean Bas and they seem to be Prett limited to you know less than 70 kilometers of of overall extension at most so once again we use geof Flac to set up a whole other set of models this is a pretty different model from the one I was showing before earlier um for instance we don't aren't modeling magnetism what we're really interested in is what does spreading look like on Venus so we've pre prescribed a crustal you know formation rate so we're adding new columns at a prescribed rate at the beginning um and that rate is independent from an extension rate which we can also prescribe it's similar to what we had before we can also vary the heat flux and um uh we also have these other you know phases worked in so like you know this is basalt crust these are the two different layers of mantle that yellow is the high temperature Shear zones that I was talked about before um but this black which gets introduced into this um this block is echate phases um so on Venus because of the elevated geotherm uh when you have uh upwelling you can actually create metamorphism just by moving the temperature or moving into a hot uh or yeah moving the temperature um which is very different from on Earth because on earth when we think about eite we think about in terms of subduction but because of the higher temperature and lower pressure it flips on Venus where you have to start thinking about EK you know in the cont of extension it getss pretty weird um so this is the model that we have set up we ran this a bunch of different times um but really what we end up with are these three big overall regimes based on how we're varing the extension rate from a tenth of a millimeter to a centimeter per year uh and then with the uh addition rate of new crust along the same um uh along the same domain and then we also just have this like binary variation of ter heat flow between 50 and 80 Ms so both kind of assume a certain amount of activity um but the key thing here is that what seems to control morphology is the rate of crustal formation right because these between the um uh the yellow which is this regime here where you have very low extension sorry you have high extension very low rates of addition so you're bringing a lot of new material up to the surface um you can't accommodate that extension so it's just this upwelling of the asthenosphere uh that's in yellow um these steady state where you're actually able to replace the new material that is be sorry you're able to fill in that accommodation space with new material uh that's in the middle here these are these two different shades of blue and then there's this uh over thickening case where you cannot accommodate the new material for whatever reason you're over thickening the crust and that creates this very distinct morphology and that's in red I'm going to get into this in more detail in later slides but the key Point here is that like you know there's these diagonal lines that split the two different um regimes the two different heat flows um so it really is a relative rate of crustal formation and extension that controls RI morphology within the model and it falls on to these three different uh regimes so here's the middle regime the steady state regime the stuff that's closest to like seafloor spreading on Earth where what you're doing is you're um just at the same rate that you're creating new accommodation space you are adding new material into uh the middle and it's a pretty straightforward thing um yeah you do get like a little bit of ecologization that is dropping off and eroding away at the lithosphere but it's not a whole lot but what you do get is you do get this new crust um uh that you know kind of gets wider wider like c4 spreading um Mor oh wait that work yeah that that was weird um so and it kind of comes in two different flavors there's an asymmetric flavor which is the one that I show here uh and then there's a symmetric flavor which is uh here but just to kind of like get you guys heads around this U fake block diagram um here is the uh surface's topography this is the time dire and then this is the actual like 2D structure of what we're doing so it's not really a block diagram it's it's not showing space it's showing time but the idea here is that you initially start with you know this you know a this axial Rift and then that spreads out and splits and because of this asymmetry where um sometimes and I think it's happens for like stochastic regions the where the uh most the extension takes place and where you're adding material tends to partition um and that's how you get a symmetry this is kind of similar to what you see at like you know the NASCAR Ridge or in other mid ocean ridges uh on Earth where you can actually have at least in the case in NASA um 90% of the accretion is happening on one side of the mid ocean ridge and 10% on the other so you can get a pretty asymmetric uh setup and that's kind of similar to what's happening here um but these are the kinds of profiles that you would get out of that kind of thing um for the symmetric version you kind of get these just like really simple erased flanks it looks a lot like a classic mid ocean ridge um these are the two versions when we start applying this to actual Rift systems though it's not to kind of spoil things it's not a great fit um so here is uh hecy uh HEC casmo which is this Rift system here um when you look at it looks like a fairly typical half grin which is not something that the spreading idea is able to you know really well like match if you squit you can maybe convince yourself that oh maybe this is a half gra and this gets eroded but there's no evidence of any kind of like structural you know uh um uh complexity on the interior of this Rift right so this is the black line is just the uh average cross-section across that whole entire RI segment um this one right here and then all the smaller lines are just all of the different lines stacked uh you know end to end um so it's not really a good fit um there's a similar story when you start looking at like Parker like the Parker chasmata uh and Lona chasma is that there's all this kind of complexity that you'd associate with like Continental riffs that doesn't really work with this idea of oh well maybe you know spreading just looks different on Venus where you have this high temperature um high pressure surface um so these diagnostic features of like this you know this symmetry or the uh um uh or that or that like broad asymmetry is really difficult to match so it's not very convincing um on the other hand oh wait that's supposed to play on the other hand right the hyper extension regime um where you have uh no new material is being added you're just pulling on the sides uh so you don't have anything to fill that accommodation space so you just create this you know like just this normal looking Rift with no new material um that so that produces profiles that look like this this big broad bull shape or you know this kind of Messier but overall still like deep broad feature um that if you squint does look like some of the Rifts like like Southern Deana casma um and also Rona chasma and a few other features um they also they do tend to fit some of them at least the symmetric Rifts um but that also could just be because you know these are full groin features and when you don't have any new material to add in your Rift if you don't have spreading you just naturally want to create a full groin in the model so you know it kind of seems to show that the global Rift an Global Rift Network maybe isn't the best analog to mid ocean ridge kind of confirming through modeling what was suspected just from the surface morphology um uh so if new crust is being formed here it's not to the same extent as Earth's mid ocean ridge and you definitely don't have the same degree of extension at Mid at the Earth's mid ocean ridge so it gets a little bit so it doesn't really work as a model um that being said there's like some locations where it does sort of work and by some locations I mean one specific unique location on the whole planet um this is the famous Artemis Corona it's something like 2,500 kilm across it's massive cular feature it's been identified for Fairly obvious reasons as maybe this is where ephemeral subduction or at least regionalized subduction is occurring this is all rolling back and maybe this could be a back Arc Basin of some sort um when you look at this internal structure you know so here's that asymmetric spreading case that I was talking about before it does seem to kind of match with uh the northern part of Brea Martis you have this clear asymmetry where one side of the rift axis is sitting a lot deeper than the other you have that Rift axis in the first place it's a similar degree of width um and uh you know and also if you look at it in map view might be kind of difficult to see for everyone in the back of the room but there are what appear to be some sort of fracture zones that link up these Earth segments but this is kind of a unique feature on the surface of Venus that does not represent almost any of the other Rift systems uh across the planet now the over over thickening regime and this is why I brought up the coron earlier if you end up in a situation where you are adding more material then you can create the accommodation space to um to make so yeah if you're adding more material than you're creating new accommodation space um what ends up happening is that you over thicken the crust the root of that crust transitions into eite phases and because eite is a lot denser and it's a lot weaker it collapses down into the mantle and uh you know you get this topographic inversion that looks like this right so you start off with this peak you get these flexural troughs on the side and then when the collapse begins that Peak inverts um but you maintain those troughs because what was before being created through flexure is now being created through sustained like Dynamic topography because you have these lithospheric drips that are down Welling and then you have this elevated bull-shaped interior um that is a little bit elevated above the background um that is then divided by these you know troughs and elevated rims um and that's really interesting because there's a lot of features on Venus that look like that the coron look like that um so there's a bunch of different varieties of coron like I said it's a morphological term there's a lot of different uh varieties uh with very different topographies but when you look at like these are all the different you know over thickening cases that we ran to the models some of these start to look really similar to the uh coron uh that have been identified in the literature um and that kind of implies that if this is true then like delamination due to ecologization might be really important and something that we need to consider when we start thinking about the origins of these features which are unique to Venus and therefore may tell us something about the overall tectonics so here's adens coron on top a Corona on the bottom you can see you know like the two profiles at the top are across at a hens and at at the bottom is uh the uh model that I had on the previous page um that over thickening model um they do have a lot of the same diagnostic features that bull-shaped interior that trough on the outside these elevated rims relative to the trough um you know it is a decent enough match if qualitative you go to some other coron like mlei and taranga and you have a similar kind of feature um where you have these troughs these outer rims this bull-shaped interior like from the previous model on the other page but this model is a bit different this model it's not as elevated and there's a lot more complexity here there's a central Peak um that Central Peak might show up in some of the other coron like Miri up here um and and there's a lot of different models that don't have this elevation and and so while morphologically they can be similar like the actual elevation is fairly different from any of these models and I think the reason for that if you cast your mind back to was explaining how the model Works we're not modeling melt generation we're just prescribing a rate of a new addition in the uh in the model so as a result there's no Dynamic uplift um there's no melt that is go there's no melt there's no upwelling that is going to push topography up if this is an active feature um so this if you bear with the handdrawn model for a second um uh so this was kind of the model that we came up with for some of the coron the rift Associated coron um this idea that maybe you have a plume coming up or maybe there's just some other form of upwelling creates new melt this melt comes up through this uh through the lithosphere adds new material thickens it there's not a whole lot of extension because there's no subduction on either end to actually pull the plates apart and as a result you just of over thicken things until you start forming this eite root and this eite root wants to drop off um and then that might be how you create some features of some coron on Venus um this so this cartoon is derived from the model um so what's interesting though is that this might be a form of recycling you know where uh where like before I mentioned how there was no you know before I mentioned how like okay so on Earth you're creating new material all along you know the mid ocean ridge and it's being laterally migrated then subducted and therefore destroyed you know down at the subduction zones if you're not creating new crust at the uh at these Rift systems except in these specific locations where Corona are forming maybe because there's a plume underneath right then what that means is is that they're also getting recycled right where that new material is being formed um so just how I had like the subduction zes outlined in white areas where stuff might be getting recycled on Venus is outlined in white here and seems to be or could be uh where you're actually adding new material um so it's all collocated and very regionalized so yeah so this is all just kind of you know what I had previously said um so to summarize it's not a good analog to the mid ocean ridge um model does seem to work for some of the coroni features but that maybe says something about how regionalized crustal recycling is on Venus and how it very much not like a mid ocean ridge so here's part three the second half of the Venus stuff which is in progress and I'm really excited to kind of show this with the limited amount of time that I have left I already emphasized that Corona are not a single thing right there's a there's a lot of different variety I'm really focused on this kind the stuff that's embedded in the rift they're asymmetric they're polygonal they have these raised Interiors with these elevated rims and these really sharp boundary troughs on either side um so here's an example of that is teranga here's the geological map that shows the lineer if you take the lineer as uh like as telling you something about the stress field they seem to form along RI with the rift um um so uh and it's also very distinct from the Sanic coroni so this is the kind of coron that I'm really interested in there's a whole bunch of these all over the surface from emis to KET lot Tanga there's a whole bunch uh and they all seem to be embedded within this Global Rift Network and they all have this fairly like generalized but like you know they they all fall into the same category of Corona where there's these they either these like large plateaus or these kind of these subdued plateaus that much of a dro the idea is that these might actually be a uh a Time series of some sort where you start off with an active Corona with high topography you get this big Plateau type you know with a positive gravity anomaly from free air um uh because of the higher topography um and then when like the plume shuts off or whatever the source of melt shuts off this thing isostatically relaxed the topography lowers um the uh boundary troughs which are being sustained by this downwelling disappear um and the gravity anomaly kind of uh for free air goes to zero and the bugay should go to zero as well as you get rid of the dynamic you know down Welling so this is the idea um so we're running a whole new set of models that actually do model melt generation now and we take the area of the Melt um convert that into a you know absolute value of the Melt create a dyke up through the surface uh 20% of that is flows on the top 80% of that is new material to be added to the crust it was black in the previous ones it's purplish blue here but that is ekiz and you actually start to get a similar feature what we showed before these two sources of downwelling occur on either end of the plume and topographically you end up with something that looks like this um where you have this you know you know one and a half to 2 kilometer High you know profile and then as the whole system shuts off it collapses down you so you get this more subdued profile without very much trough on either side which is very similar to the uh to the cartoon that I showed before um so right now I'm in the process of going through and Le last like 3 minutes of going through uh all these different Rift embedded coron on the surface try keeping track of what is their average elevation uh relative to the surrounding planes what's the frier anomaly like what's the buget anomaly like and seeing whether that matches up with the predictions made by the uh made by the models preliminarily what you end up with is circled in yellowish white is these areas of Fairly High topography fairly deep troughs embedded within the Rifts and then in red are in are coron that are embedded in the Rifts that have fairly low topography the trough is pretty you know subdued to non-existent um and so you know but and they cluster geographically um and you know what whether or not this is a real signal is remains to be seen because when you look at free a anomaly what you see end up with and it's kind of hard to tell in this image but what you have is uh these areas of high positive anomaly in the uh in the supposedly active um coroni and then it's fairly subdued in the red circles where there's where like we hypothesize that there's not very many active coron um that the riv system might be somewhat dead um so one of the things that I really want to do is I want to go through this more system ially I didn't have time to get it done before this talk but I'm really excited to show that when the time comes um but they do seem to kind of like these two types I can now put numbers to them of this uh that active type you're generally more than a kilometer and a half elevation above the surrounding plane you get this big Plateau type you get a positive free air anomaly of about greater than 50 milligals uh for the inactive quote unquote um type it's less than a kilometer sometimes down to half a kilometer um you get that subdued uh topography you also have a a positive anomaly that's less than 20 milligals um and then next step is to start looking at this stuff in bouay and start interpreting that but that's difficult because this is the uh resolution of uh gravity anomaly for Venus it's highly variable across the surface um and uh you have pretty good up to like maybe you know 90 something uh degrees in the interior um sorry around the equator but in the Southern Hemisphere and the Northern Hemisphere but especially the southern hemisphere it can get all the way down to like 50 um and what that means is is that features that are less than like 300 kilometers become almost impossible if not completely impossible to resolve correctly um so interpreting the bget and Freer anomalies to kind of to match up with the models becomes very very difficult but one of the things that could come out of this is we could start making uh predictions um for future missions so Veritas is actually going the Veritas mission is going to improve on that global map within the next decade um and it's going to be amazing it's going to fill in those holes we're going to get higher degrees might we might actually be able to resolve these features in free air and bugay we also because it has insar we'll be able to get deformation of the surface um is a similar story with the uh vensar instrument on board en vision from the European Space Agency which also comes along with um with a ground penetrating radar so we'll be able to make predictions from these models that can be addressed by Future missions and future data sets and yeah that is oh yeah and then the tie it all back together this my last slide to tie it all back together what I think the big takeaway of all this work is is that these relatively small changes and heat flow surface temperature thickness of the crust can end up manifesting and completely different styles of global tectonics and geodynamics and I think that's really interesting and that's kind of what's motivating me to keep on working um thank you very much that is the end of the talk I'm having to take [Music] questions I don't remember that was someone said something online oh hi Sean um okay yeah if anyone has a question yeah um so on the surface temperature grad by the way but um on the surface temperature how did you treat that did you deal with laps right or did you deal withing um surface um we set the surface temperature in the models to 470 and and didn't vary it um across the surface because Venus's atmosphere is pretty thick there's not a whole lot of variation across the surface so we essentially like anchored the geotherm to 470 at the top and then we have like a free boundary at the bottom so it's allowed to vary depending on uh kind of what happens in the model there is variation what do you mean by laps rate just get cold you get higher oh yeah sure but we're not modeling the atmosphere like at all we're just looking at like the top of the model is the top of a geosphere okay we're not modeling atmosphere at all okay though we do apply a pressure but it's like a uniform pressure the surface yeah sure so the Mell topography especially in the the rift areas sucks yes a you the uncertainties we tried the best we could which is basically we picked segments along the rift that seemed structurally pretty similar and then averaged across that basically average the long strike variation to hopefully come up with a topographic profile that was close to average um there's really not that much we can do about how much it sucks in other respects especially around the Rifts right with only left looking radar um there's only like so much you can do my understanding is is that new data products are going to be coming out because people are taking a second look at mellin ahead of the New Missions so I'm looking forward to when that data set comes out I would love to play with it but right now there's I can only do so much and I have whatever I can and I haven't done that much much more than what I've already said I like an ensemble statistic question yeah um so I think it was in your second chapter you said that there's like this this diagram you have like three different regimes and it's just like a handful of t whatever a lot of the plots that you showed like it was like 500 plus like members like what made those what do you mean like 500 different like model runs how many oh no no no no there was only 18 model runs if you're thinking about the like hundreds of points that's the actual topography got from like one or like different sorry I was are you talking about are you talking about that that's time you go to to there yeah uh these are just cross-sections of the actual topography that have been stacked okay that's all that is from one model not from a model run from the actual mellan topography this is the model in blue this is all real okay ask a stupid question yeah how do you know these linear senous features are are rather than compression um these be compressional they're probably not compressional uh you can see displacement of craters and of volcanoes across them where they're clearly extensional and also if you look at them in the limited amount of profiles that we have it is very clearly like they're either half grain or full grain where the bottom has dropped out on there's these like really strong scarps yeah um there are compressional features else on the planet they look very different yeah since you're here I think is it the next slide around here one where yeah that's it yeah yeah so talking about this whole feature I think I ask I forget the bottom there the the feature that's not captured that's predicted the model which doesn't show off at all just like w oh yeah yeah this yeah um so in the model right we have no Dynamic uplift we also have in this version of the model we also have no like sedimentation or lava to infill anything so this is probably like an artifact from the fact that like we're not making any new material that can flow otherwise this would all be infilled or maybe wouldn't even form because you should be having like uplift that creates something very different so like if we fast forward to the slightly more realistic model that I am still working on this one that actually has the Melt has the Melt flows and and you look at the topography that W ceases to exist so I think it's an artifact of the way that we formulated spreading in the first model that's a good yeah and then and then does that also smooth out the troughs on the outside get out there yeah it smooth the troughs on the outside as well for sure which is something that I'm kind of interested in because the troughs disappear a lot so now I'm wondering like oh are the troughs that we actually see in on in the actual Topography is that you know are those like other Rifts that kind of you know Circle on the outside of these features are they subdued these ones yeah are more subdued go back to yeah yeah Story I mean it could be there's a lot of variation I'm still trying to Grapple with a way to like okay how do I do this in a bit more of a quantitative way because at this point I'm just kind of looking for these what I believe are diagnostic features across these different uh you know topographic profiles and across these models but to do that statistically is a little bit more challenging and there's a lot you know because there's like 18 models and I have something like three dozen different like profiles and comparing all of these you know that that number blows up very fast so I'm still working on doing that in a way that makes sense anyone online uh I saw like a chat where did it go oh I just oh thanks Cole hey Nick I'll ask one quick one uh at least I think it's quick um how are you guiding the volumes I guess of the equitization of the of the the Downs in this what's the parameter that you're tweaking yeah okay so what we've essentially done is we've created a peie wise function that Maps out what the echi face space should be on Venus and any basal or any yeah basically any Basalt that crosses over that line uh is recoded as eite with a whole bunch of different rological parameters and then beh as it's you know supposed to behave and and I guess the followup then is there inherently a strength or a connection between the part that's gone to ekoy relative to the basaltic part that has not yet in other words does it have a slab pole kind of dynamic as it starts to go down yeah um let's see I'm GNA go back to this one and kind of show yeah there is a bit of that where what happens is is I think like this eite drip Falls and then drags some of the BT with it and then drags it into that regime where it should be able to ekiti and it kind of runs so there's harm you once called it like oh Harm's not here anymore um harm called it like Phantom seduction once because it's not really slab pole but it's kind of acting like a really small version of a slap but it's not coherent yeah it's more from a flow perspective than a coherent plate concept I guess yeah neat okay thanks this model needs to be improved as well like but this is kind of the preliminary stuff

Channel: University of Texas Institute for Geophysics

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Length: 57min 39sec (3459 seconds)

Published: Thu May 02 2024