Eocene M - Near Trench Magmas w/ Jeff Tepper

hello everybody welcome to ellensburg washington usa it's winter time on a wednesday afternoon we have plenty of snow on the ground and we've got another i don't know what is it 10 to 12 inches starting now and continuing through the night winter storm warning here in ellensburg for goodness sake so the local time is 1 47 in the afternoon and we will begin our program on near trench magmas at two o'clock so that's you know that's that's 13 minutes from now i started a couple minutes early because i saw that we have more than 200 people already who've been waiting to get started with us and also it's been two and a half weeks since we've done this so i can't remember half the stuff i'm supposed to do so um [Music] one second that's volume is off this volume is off hopefully my volume is on so let's say hi to a few folks and also of course ask are we five five by five here uh for the first show after a long break geologically speaking that's todd in southern california you see it says 5x5 and northwoods 3d from northern wisconsin 5x5 as well let me slow down the chat boy okay going way too fast so i'm going to scroll back here and just say hi to all sorts of folks happy new year everybody lawrence is in meridian idaho i'm back a ways jim's in portland oregon uh simon ike togenbach from tolgan norway hello simon bernadette finally got a chance to watch live well welcome bernadette in connecticut five by five he says the geek is in alabama kamloops bc that's pamela kevin's in fall city washington usa oscars in san diego oscar 5x5 so far running on empty from snowy wisconsin john uh yeah okay kent taylor from mckinley mckinney texas come on boy i'm rusty i got to pick up the pace i got a lot of people say hi to what are you doing jeff's in west palm beach florida little bear is in flagler county florida scrolling now terry's in bend oregon maryland austin texas webb wisconsin webb lake wisconsin redmond oregon oh i'm down to live automatic scroll warden washington milwaukee oregon that's absorber for portland i always feel like i have to say that marumbina melbourne uh australia hello ian gordon's in glasgow scotland scrolling back again i missed a bunch navarre minnesota eastern kansas dennis is in dorset uk the jurassic coast dave's in bremerton washington heidi's in hood river oregon it's always a thrill always a thrill to see everybody here harlan iowa san francisco bay uh california vienna austria hello crown house kirk from philomath alberta gary's with us locked to flambeau wisconsin hello gene back country gary is that mount baker ski area yeah man that's a place to be on an afternoon like today gary i'm great you must have wireless in the lodge or something i don't know or cell coverage up on top or maybe you're skiing gary as you're as you're watching and typing what gareth the dutch night out from the netherlands gnarly is still in ecuador amazing person amazing videos itchybootch.com okay uh yeah it's 150. i do have a couple of quick stories and i guess thank yous varde denmark hello carolyn is in the uk red lester's in london bruce is in thunder bay ontario erie pennsylvania of course i can't stop okay come on boy come on boy all right so um i didn't do anything over the break well that's that's that's not true so i love working on this stuff i just i just love working on this stuff especially early in the morning before everybody else is up our house was filled with filled with family but uh everybody sleeps in and i'm up at 4 30 or whatever so you know i'm emailing geologists on christmas morning [Laughter] i know it sounds like i'm a monster and i would like put a preamble to the email i know this sounds weird you know i know i know it's weird i'm emailing you on christmas but nobody's up yet and i wanna i wanna get a few things done so with that said uh the only thing i did officially for my kind of outreach quote unquote a lot of quotes already is i did a couple of audio podcasts i don't know if you listen to the audio podcasts that i do but they're kind of a compliment to what we're doing here and i think it's different than what we're doing here and this is the first i got a package yesterday here at school from somebody who listened to those two audio podcasts that i did like right before new year's and all i'll say is thank you i got a big kick out of it i was in an air room somebody else is in the mail room you know and i'm just start i'm just laughing hysterically and they're like what's up with you i'm like well check this out i got a red ear turtle shell mailed to me i think it's fake but on one of those podcasts radio episodes i call them i had an idea for an analogy that we're going to use in february but i'm going to use this turtle shell so thank you whoever no there was no note or anything but thank you got it got the turtle shell and speaking of stories over the break we have time for this yeah okay i i already forgot now uh so i'm i'm i'm 5x5 first of all double checking i won't have to think about it again we're good there lappy working okay we doing okay there because i'm about to do the old switcheroo i want to use the ipad and to do that i need to thank you i'm going to get the power out of the laptop gently come on i'm using the other port to plug in the ipad don't have a frozen phone okay so can i switch over yes i can so have you well first of all it's 27 degrees winter storm warning we've already covered that uh for your early arrivals let me share with you that we're back to our two sessions a week and that will be the case all through january and february so we'll get to zed we'll get to the end of the alphabet february 19th that's where we're headed but that's not why i wanted to go the ipad before we started have you seen this clip before i'm going to play it and i don't know if oh i forgot to email the guest hang on hang on hang on hang on uh coming back i gotta email our our guest geez so busy with my stories and everything give me a second we do have a guest and okay it is on it is amazing how much you forget you know we've had a few weeks off and i've forgotten half of this tech goes tech stuff it's crazy we got more than 500 already wow okay back to the ipad uh actually no so i'm going to play this clip for you i don't know if you can hear the sound or not there's a bad word in it but i want to show you the clip and some of you if you follow me on social media know why i'm showing the clip but anyway here we go so i won't say anything because i don't know if you're going to hear this audio or not it might be loud anyway here we go actually tell me if you can hear this can you hear me talking right now in the video clip no audio okay good good so i've got this on a loop so i don't know how many of you have seen this before but you'll notice that this was filmed 10 years ago 10 years ago and it's the first day that i was out it was i think it was 100 degrees and i was out with tom foster rest in peace and tom and i filmed the first was the first attempt can i get rid of the pause thing why is the pause thing on there so people seem to really like this clip and i've shown it off and on over the years where we hike out to this remote place near othello washington these are some basalt columns it's got nothing to do with today's program but we lugged the ladder out there we logged audio equipment out there it was just two guys we didn't know what we were doing we set everything up and i took my hammer and down the crack it went and i didn't have another hammer and tom really wanted me to use a hammer to bang on those rocks so we went home and we came back the next week and i brought another hammer and we we finished working on that episode and that hammer has been down that 50-foot crack for 10 years for 10 years until christmas eve i get an email from a guy named andrew who lives in albuquerque new mexico hang on i've got to stop this and so andrew sends me this email and says got something i want to drop off at the house are you at the house can you give me your address i'm driving from albuquerque to my parents house in western washington and i just entered washington i want to drop this off andrew from albuquerque went out to that exact spot brought printouts from the video figured out which crack i dropped the hammer into 10 years ago and i posted a little video of andrew explaining to me that the entire hammer was buried in sand it was probably less like wind-blown silt that went down the crack but he said everything was buried with the hammer except for just this very uppermost part and andrew is a computer engineer and at the time he was living in tri-cities washington working for a national lab national lab and he brought out a bunch of what did he call them hard drive magnets i don't even know what that is but a bunch of very super powerful magnets on a string lowered him down he says the magnets grabbed on to the end of my hammer he had to work the hammer back and forth pry it out of the sand as he calls it and got it up and the punch line is he did this in 2017. so i can finally share my secret which is i regularly take students out to that crack they want to see the crack where i drop the hammer and between 2012 and 2017 i would show them just the part of the hammer that we could see down there and a few came back out with magnets and they tried to get them out but they weren't andrew but andrew got the hammer out of there in 2017 and since that time in the last five years when i take groups out there we look down and they say i don't see the hammer and i'm like here's the secret somebody took that hammer somebody got it out of there way down there they got it out but i have i keep waiting for somebody to tell me they have it well andrew the panda pandemic happened before that he was waiting for just the right time to present this hammer to me at a public lecture and that didn't happen in the meantime andrew moved to albuquerque and packed up all his boxes from tri-cities including the hammer the hammer was down in albuquerque for a couple of years or whatever anyway that's the long story and uh andrew uh from albuquerque thank you for returning the hammer and that's my little story a christmas miracle as i call it now it's already after two o'clock okay we have 700 people with us uh here's to you for joining us would you give me one extra minute to get my head right now that i've shared that story and we will begin talking about near trench magmas thank you hot mike okay our guest is there i saw him in the green room so i see you guest that's good i'm glad you're with us i'm off camera i'm mumbling to myself you can do this now boy you're talking about near trench magnus you can do it game plan what is it right and talk about that and then that yep yep okay oh i think you can do this i believe in you i think you can do this good afternoon everybody and thank you for joining us i'm so glad that you're with us on this snowy wednesday afternoon here in ellensburg washington usa we've been off for a couple of weeks two and a half weeks to be precise and we're back to our wednesday afternoon saturday morning schedule and we will be with that schedule the rest of our time together as we work our way towards session z this is the crazy eocene a to z and that's fine that's fine that's the plan but i i do feel like i want to give you a general sense for the next month and a half i do have a general plan most of this month january will be devoted to magma and we know that magma is just one of the eocene fireworks that we've been talking on before the break i can't remember who sent me this last year but thank you very much for that need i remind you that we have our cretaceous fireworks our crazy e has seen fireworks i said cretaceous wrong the crazy you've seen fireworks and i'm the first message today is that much of the month of january will be devoted to this chalice magma thing and so our guest today is a key person to help us understand how these chalice magmas are different than other magmas he's going to come back i'll tell you that right up front he's going to be back we need him more than today he's going to become coming back again in two weeks that's the plan um but before we end the alphabet series i do want to get to these guys as well the crystalline core and these metamorphic core complexes so that's february so generally this we this month is magmas is magmas and ocean plates even though i've tried to avoid thinking about ocean plates i have to deal with ocean plates a little bit and then february these mysterious rises of these metamorphic rocks these metamorphic complexes this exclamation business and the crystalline core and so on okay so that's the plan generally and before we quit i'll show you the schedule of sessions but again it's easy to remember wednesdays and and saturdays wednesday afternoons at two saturday mornings at 9 00 a.m pacific time and i've noticed that many of you have gotten yourself caught up you know the holidays were a busy time but i i every few days i check the view numbers and and we're up to you know whatever it is twelve thousand thirteen thousand views for most of those videos now in the series so congratulations and thank you for your interest you're up to speed and you're ready to go we did do some things before the holiday break that i do want to revisit today so what we really are doing two things today the first thing we're doing is reminding ourselves of a couple of themes that we established with a and fireworks both back in the cretaceous time related to rangalia and a more recent story with eocene and the rustic sourdough which was moldy this morning i just realized i threw it in the garbage i was going to use the rustic sourdough again but i guess you can't keep a loaf of bread in an area for three weeks without problems ultimately our guest is going to help us see some key differences between magmas generated by subduction to create a volcanic ark versus magmas that are somehow generated in something called a slab window and that includes some of these things called near trench magmas so that's the new wrinkle today so it's a combination it's a one-two punch today the first punch is going back before the break and kind of resuscitating some of those themes the second punch is brand new ground with these brand new kinds of magmas that i need some help explaining and our guest is the perfect person to do that okay so without further ado we're going to go here in here but i guess there is in a do i guess there is something i want to do first i went back to the i'll show you i went back to this grant proposal that was written a couple of years ago the north cascades team the dre team you've met two-thirds of them now mike eddy stacia stacia gordon and bob miller stacia's coming in february but you've met mike and you've met bob we might get them back again but i'm proud to report that after a month of doing this kind of stuff with you portions of this grant proposal involving new research in the north cascades of northern washington made more sense to me than they did a month ago feels good i'm making progress understanding some of this stuff and i think we all are together so one thing that i want to pull right out of the grant proposal is a nice way for us to review where we were and if you have an excellent memory you remember in our session a there were these things called magmatic flare-ups that mike eddy in particular was very interested in but bob and stacia as well i took the time to write down these magmatic flare-ups in other words these plutons we are talking about magmas today and much of the month so please ignore that this is the state of washington that's i'm just using a chalkboard here for space it's got nothing to do with the geography of washington and i'll just do this verbally because you can see it more than anything else in the north carolina i said ignore washington but now i'm going to point to it you can see i think can't you that this is the state of washington seattle's right here and underneath all this text is eastern washington that's full of snow right now and in north central washington right here on the map i'm not looking at the text yet is the north cascades i think we know where those are by now well as the grant proposal is written mike and friends are saying look there are lots of plutons there are lots of magma bodies in the north cascades and they fall into three generations there are cretaceous granites and other plutonic rocks and even some volcanic rocks i think that are between 96 and 87 million years old examples the mount stewart pluton i've heard of it it's right the frick over there man black peak pluton 10 peak pluton seven figure jack pluton i don't know hardly anything about i don't even know where most of these are i think bob in one of our shows said the ten peak plutons up by present-day glacier peak volcano but i i know almost nothing about these plutons but what's new to me and really this is i'm trying to frame our discussion for the entire month of january is realizing that we have three distinctly different flare-up events or magmatic generators in the cretaceous during these times in the eocene yeah you have seen fireworks the chalice magmas between 50 and 45 million years ago yeah we're going to be here today we're going to be in here much of the month this is the crazy eocene is it not and these four plutons are going to be studied carefully by the end of the month but there's another batch that don't make any sense to me and if you remember the mike eddy show he said the volume of this these plutons are a little bit wimpier in volume he said these are very voluminous very voluminous so the magmatic flare-ups were monstrous in the cretaceous and in the eocene and by comparison mike almost said it's kind of a push to even call this this collection of plutons between 78 and 60 million years ago flare-ups but there's enough of them again i don't know anything about these and they're kind of in in-between times i think bob miller said that in between these two major magnetic flare-ups we have this kind of i don't want to call it a minor event but the big thing i'm trying to do for us here oscar color chalk is that we have established and this was on purpose we have established before the holiday break that a major event was docking rangalia and friends you remember that that's the 100 million years ago and then inland from the docking of rengelia and friends the insular super terrain we have a bunch of thrust faults and plutons is this truly a bunch of subduction related magmatic arcs or something else up here at the top we know the rustic sourdough is coming in and these are happening shortly afterwards the fireworks in the eos scene well we had cretaceous fireworks as well if we jump back and forth between these two major magmatic flare-ups this is the theme for this month yelling i'm excited to be back with you if we keep jumping back and forth between the eocene and the cretaceous between celestia time and rengelia time what kinds of parallels or super huge contrasts can we make between these plutons and these plutons between these volcanics and these volcanics between these gold and silver deposits and these gold and silver deposits if there are any and then what the hell happened here to my knowledge and i think to anybody's now is there wasn't a major terrain accretion at this time but maybe there was i don't know and we're saving baja bc till next winter so i i don't want to go there but to me this is intriguing so we're going to be jumping back and forth between three major time frames and it's all centered on the north cascades i hope you know that's why i'm doing this i want to learn new things but i keep asking myself how is this going to help me better understand the north cascades and these three magmatic flare-ups is one way to do it now another way to give you a visual for that and i'm going to try to do this quickly because i got i want to get to the the content of our guest this is going to go quickly i hope because it goes along with what i just said here's rengelia on a map this is a hundred million years ago right here's celezia on a map this is 50 million years ago correct can you get a sense of what i'm trying to do this is a map of the west this is a map of the west here's our large igneous province offshore celestia it's a local hot spot creating a local large igneous province greater celestia half of it's going to end up in alaska called yakitat we know that but going back to december we talked about rengelia potentially sitting on top of some hot spot maybe down by the equator uh more than 200 million years ago and it's not until 100 million years ago that this rangalia hits and if you remember the basil story the basil tickoff appearance he says we don't even really have washington and oregon yet a hundred million years ago and everybody whether you are a mobilist or a fixes whether you are a pro-baja bc person or someone who just ignores the whole thing that's a lot of people regardless of which camp you're in everybody agrees that this rengelia which is a cold and complicated super terrain insular in other words that thing is docking at least idaho but probably idaho in many points further south so oscar i'm going to use your colors here what are these things oh i'm getting i'm i'm fully excited now so we're accreting rengelia 100 million years ago what's happening in board the green doesn't stand out that well to me we have thrust vaults and plutons rengelia docks 100 million years ago it's the same view from the side remember thrust faults this is the bob miller show and plutons rising the age here is i don't know 96 to frickin 87 or whatever it was you got it just like the north cascades thing this is the kind of general kind of big picture view of the tectonics at least in my brain for the cretaceous plutons the cretaceous magmas that are in many places in the american west but especially in the north cascades yeah the mount stewart pluton yeah the ten peak and then whatever peak and the seven fingered whatever jack here now for our discussion today red how are we generating those magmas back in the cretaceous remember we keep jumping back and forth this is 100 million years ago are these magmas from subduction of an oceanic plate i think that's the common company line but i got questions in the cretaceous where's the ocean crust to subduct to make those plutons if they are younger than the accretion of the insular super terrain are these magmas more of a slab failure story bob hildebrand where we break a subducting slab and mantle material hotter material comes welling up leave it alone you know why because that's another thing i did when re-reading when re-reading the grant proposal these guys are ignoring the cretaceous i blame basil i'm interested in the cretaceous really for the first time in a serious way and these guys go i don't think we're that interested in the cretaceous we're not going to spend much time thinking about the cretaceous plutons maybe because of kind of these major questions that i'm thinking about now but probably a bunch of other reasons as well but these guys are devoting most of their time to the other two so the north cascades research team the dream team you know that i'm associated with them for the next few summers they're not really going to be sampling cretaceous rengelia related plutons but they are going to be spending a lot of time sampling the in between times plutons it's a super mystery to i think everybody as well as the eocene plutons that have been studied a fair amount already but there are significant questions okay let me continue with my story because i'm going to leave this because they're not going to spend much time thinking about it but again i think it's helpful to go back and forth between these two major events where the plutons are on display in the north cascades if we have a more local hot spot and we do and therefore a more local terrain and we do it's greater celezia that's essentially 100 crescent basalt and other kinds of basalts and we accrete that i'm not going to do colors again yeah we decided that there was thrust faulting for sure the cowichan thrust for instance in british columbia between 51 and 49. but i've been thinking about this over the break and i think i have a new message here are there plutons associated with the accretion of celestia like it appears there were plutons associated with the docking of rengelia and friends in other words are there plutons generated from this collision and you're like well of course there are look there they go there they are those are the easing plutons between 50 and 45. well these are all from extension as i understand it so i'm slowing down now to help us see that something funky is going on with these eocene plutons we're finally to where we will be the rest of the month these magmas are weird yeah the golden horn the cooper mountain the duncan hill the railroad creeks they have to look i haven't even learned them yet but they are rising in board of the docking of celezia but they are rising during an extensional time ext in extensional time or more accurately they are arising during a trans tensional time remember we did that with aaron donaghy before we quit talking about the chump stick weekend before the break trans tension is a combination of extending the crust but also doing transform action remember the strike slip basin the chump stick is sitting in that was a transtensional basin you pull the crust apart but you also wrench it sideways as far as i know these cretaceous plutons are not transtension they are trans trans i always stumble on that transpression why do i stumble on that transpression during the cretaceous that's a combination of compression and transform activity also wrenching but it's a squeezing and shearing as opposed to an extending and shearing so we're getting these eocene plutons is my point with a different kind of a structural geology setting it's not pure extension but its extension and also this transform activity i gotta add a couple more words and i am having fun with uh with all this colored chalk so thanks again oscar please recall ah thicken can you read that in purple i think you can many of our guests before the christmas break kept talking about the cretaceous being a time when we are adding to the thickness of the continental crust at least here in the pacific northwest but maybe much more regionally than that remember basil was tying this to forming to kicking off the rocky mountains but let's keep in mind that our cretaceous story is a compressional story even though there's some trans form activity but we are doubling the thickness i don't know we're adding to the thickness a significant amount and what's the opposite of thickening thin the crust so this eocene magma time which our guest is about to talk about whatever whatever the magmas the the magmas are weird they have mineral assemblages that are weird there's other things about this story that are weird i'll just keep using that word today because it won't take a month to really think about them but the weird magmas are coming up between 50 and 45 generally when we are thinning the crust and a lot of other stuff is going on as well i can't hold it now remember in the crystalline core this will be february we have this incredible going up the geologic elevator the examination i won't bother to write the word but that's tied to this and i'm fuzzy on it but i think possibly some of the geologic down is after the docking of rangalia so am i all over the place i don't think so i think i know what i'm doing at the moment for a change i might have to screenshot this one or do something i don't want to erase this right away i'll probably save it for the next couple of sessions maybe i don't know but this is kind of our roadmap to realize how this local time is important to us all right i'm satisfied with that kind of reminding myself of what we have you remember i get a frozen phone uh if i have too many things plugged in at the same time so before we go to our guest yeah guest give me 10 minutes and we'll be ready for you let's go to the ipad and i want to share a couple things to kind of set up that discussion with our guest haven't really gotten to the near trench magmas you keep waiting for it but i felt like that was i hope that was a wealth worthwhile um review session to get us back in the flow more than anything else okay so i showed you this before i think i have it on a loop this is india colliding with asia but i want you to notice that there is a failure of the slab a failure of the ocean slab that's happening right beneath do i have a pointer yeah oh pointer i'm going to put the pointer right in here get the pause button out of there hey get the pause button out of there thank you okay i can't have the pointer then i'll just keep this on the loop and show you and try to give it to you verbally that is as soon as india the continent of india starts colliding with the continent of asia all i can do is use my words notice that that little thin little ribbon of ocean floor detaches from india and as it detaches we're literally breaking the ocean plate down below that's what i mean by slab failure and obviously if i'm introducing it right now we're going to think about some of that in the next couple of weeks move on boy oh boy we got our our up at mount baker maybe he's still watching or in the lodge or something backcountry gary has been busy sending me photos annotated by himself gary back country ranger long time and the north cascades is where we go this is not gary but this is from the grant proposal and do i have my pointer now he asks himself no i don't um the bright reds are the east no is that true the bright reds are the cretaceous plutons in the north cascades mount stewart 10 peak black peak for instance the oranges are the eocene plutons in the north cascades cooper mountain duncan hill golden horn daddy's proud of himself he starts to understand a few of these things remember this photo really caught mike eddie's eye where he said i don't know where that is i we were trying to map where these two plutons and eocene pluton and a cretaceous pluton came in direct contact and that's definitely what we have cretaceous on the left potentially related to the docking of rangalia he has seen pluton on the right potentially related to the collision and docking of celezia but again remember as i'm understanding it currently i might get talked out of this the pluton on the left is from a transpression scene and the pluton on the right is from a transtension scene why are we making these magmas in a time when we're pulling the crust apart that's our key question today i mean gary's going nuts here with these photos and all i'm doing as i'm looking at these photos for the third and fourth time is i'm thinking okay rangalia or celezia do you know what i mean i'm thinking about the fireworks after the docking of either rengeli and the cretaceous or the celezia in the eocene now to set us up specifically for our guest we're going to visit a couple of places in western washington like bald mountain and compare it to the golden horn which is in eastern washington so this is not really in the cascade this is in western washington this is a place where we shouldn't even have magmas it's kind of weird bald mountain mount pilchuck huh where are we hell that's everett washington that's i5 on the horizon these are all gary photos pearl luminous okay now i'm getting queasy i don't know what these words mean per luminous does that mean it's got a lot of aluminum oh really what's happening who gives it we're in the wheelhouse now of our guest but roughly at the same time that we're getting magmas in western washington we're getting these crazy eocene magmas in eastern washington like this beautiful photo of the golden horn batholith up by washington pass where i shot a video last september if you happen to see that one so we'll continue to get gary's help midnight peak volcanics i think those are cretaceous i think that's from rengelia time okay you saw our show with ray wells and we focused on celestia what did we artfully avoid during that entire show we've got a spreading ridge look at this thing he's got a dashed or a dotted spreading ridge or a plate boundary coming right between these two ocean plates the coola plate and the farallon plate according to ray wells and this thing is heading right for us i focused only on the sourdough bread out in the water purposely avoiding a plate boundary that almost certainly was centered under greater celestia we're not going to look at the animations now but when we finally dock celezia we have all sorts of cretaceous fireworks happening inland okay before i unplug the uh ipad for purposes of power let me make sure that you all know that january and february viewers you are welcome to come back we're going to be at this every wednesday and every saturday morning there are the sessions in january there are the sessions in february it will be done february 19th i'm not looking forward to being done i'm having too much fun with this stuff okay i'm unplugging the i'm going back unplugging the ipad trying not to freeze the phone our guest is being very patient thank you for that i got one more thing to set up our guest and then we go to him so it's official i am now out of my comfort zone because i'm talking about places that i barely know and magmas that i barely know but i want to remind you that our well-known cascade volcanoes known as a modern volcanic ark a magmatic volcanic ark which looks like that right subducting oceanic plate volcanic arc magma is coming up from a subducting plate we've all taken geology one or at least read something online we know what subduction looks like we know that magmas are typically coming from a subducting plate we know that a volcanic ark is the result of that and something called the four arc is this place between the ocean and the ark and the forearch is typically a cold place you're typically not making magmas in the forearc because you haven't gotten the ocean plate deep enough to generate these melts there's an angle to the subducting plate in other words so four arcs are cold four arcs are not places we make magmas typically we have to wait until we get past this area and get to the actual volcanic ark to get this incredible stream of magmas coming to the surface well the modern volcanic ark that we know and love here in the pacific northwest goes back about 45 million years i told you 44 before the break it's now 45 according to our guest but we are going back earlier than 45 million years ago to the crazy eocene and these stars on vancouver island and these stars in the forearch of the pacific northwest are magmas and the question is what do you do with these magmas what are these magmas telling us these are magmas that are too close to the trench to be easily lumped in with a volcanic ark these are near trench magmas the oceanic trench is offshore or even was we bring in a subducting plate what's going on last comment near trench magmas are important to us because they mark where an ocean spreading ridge out in the water is intersecting with the margin of the continent let's say it two more times near trench magma is in their most classic sense are important to locate and study because the most convenient interpretation of those near trench magmas is we're making magma so close to the trench in a nor place that's normally cold because this is a divergent plate boundary where we have hot mantle coming to the surface and we're actually making two ocean plates that are eventually going to be heading down a subduction zone in a trench and yeah we're going to get volcanic ark this is arc here this is volcanic arc here those are majestic shield volcanoes in general but look at what we have right here at the place where we are subducting a spreading ridge we get near trench magmas at the coast and we have something called a slab window where we have more of these funky magmas that are not typical of a subduction zone so right now we're going to our guest and i have questions for him about the near trench magmas that he has studied with his students other magmas that he has studied in a slab window and then in the last 20 years some of his discoveries have helped him see that there's some funny business happening within the slab window but we'll save that for january 19th okay 238 not incredibly late for our guest but thank you for your patience let me take a moment i've got volume off there volume off here the scroll is still happening so it looks like we're functional we've got 900 people watching our guest is from tacoma washington and his name hey is jeff tupper how are you today jeff i'm good how are you i'm doing well university i'm having fun man university of uh puget sound geologist geology professor jeff tepper we tested out the the tech yesterday and i think we're doing okay again right there's no you're doing fine on your end with audio i don't hear any little egg timer this time okay okay good well let's jump right into this jeff um first of all can you give us a little background have i don't i didn't post a paper that you've written on this because you've been more busy with with what over the last 20 years other projects no well it's mostly an abstract form at this point so okay student theses will eventually turn into papers but it's slow so you've had uh over the last 20 years with your geology majors at ups how many class projects where you've kind of devoted to these really crazy eocene magmas probably nine every other fall for 20. every other every other fall for 20 years and what has been the procedure so you go to a different location each time and how do you pick your locations about where you want to sample rock well the first one was totally fortuitous i just wanted to go somewhere on the west side of the cascades in february and so that launched the whole thing because we found some etiquettes which i knew nothing about never heard of them before after that all the subsequent projects were um something eocene something that hadn't been studied um in terms of modern petrology so they've been mapped so we would know where to go and we do we don't do much original mapping but we do metrology so something had been studied before and then something that was accessible so had logging roads or some other uh easy access so in a weekend for example we can maybe take two weekend field trips and collect enough samples to to support the project so this is great so have you visited and sam can you give us some specific locations in western washington that you still view as pretty classic near trench magmas okay now you're breaking up a little bit for me i don't know about your viewers let's uh uh kind of a frozen am i still breaking up your audio's back but you're a frozen uh frozen video what did we do last night i'm not frozen what i can see uh they're saying no audio for jeff now the audio is back yeah i think they're experiencing the same thing i am so i've got your audio but i don't have your video um so i keep talking do i still have audio i still have audio but frozen picture look let me oh there you go there you go just gotten right back again we're back we're back must be all that snow over there in tacoma it's mostly rain today yeah so do you do you have any that you feel fit into this simple narrative before we get a little bit fancy with a couple of other things so two the beta kits at chemical rock outside of port townsend okay and something called the grey's river volcanics which are in southwest washington north of the columbia two very different locations in washington is that and i don't want to get too fancy right off the bat but does that mean the the subducting spreading ridge was that wide or are the ages different between those two um the ages are different the edges are different and ridges migrate along the coast there we go and ridges can be offset by transforms so you can have actually two um intersections at the same time so let me try to keep up with you so you got some water there are you okay with your throat yeah okay oh nice mug let's see that mug that's geologic time oh is that the one with the trilobite in the bottom of it it is okay yeah pretty cool um so chima come up by port townsend do you have a date uh in your mind um yeah 47. 47. and then the gray's river is greater than volcanics that's more like um high 30s low 40s okay so younger to the south but different ridge you know okay bridge different segment of ridge the original i don't think the ridge was moving southward okay okay yeah i this one's going to be a little awkward not between me and jeff jeff's been very helpful over the last couple of years teaching me a bunch of this stuff but i'm i'm going to be flirting with certain things and then i'm going to back away because we've got some complicating things that we want to address in a two weeks instead of right now um so in the slab window itself can you help us compare between if we have a magma related to a volcanic arc and subduction versus magmas that are what's different about this slab window it looks like a totally different story what what are some differences from your world between slab windows and volcanic arcs okay so if you think about what's happening offshore at a spreading ridge you have magmas coming up from the mantle and those would look like what you would get at a mid-ocean ridge yep okay if you move inland the same thing is happening the source of the magma is below the subducting plate so in a volcanic arc the source of magma is above the subducting plate but in a mid-ocean ridge or a slab window the source of magma is below the plate okay okay so as a result in the area that you've labeled slab window there you would be more likely to get things that look like mid-ocean ridge basalts and the only complication to this is that on the way to the surface those could cause melting of the crust so you could wind up with both mid-ocean ridge looking things or things that look like melting of the crust you really do have some true mid-ocean ridge basalt occasionally in a slide you could yeah because a slab window is just a an opening through the slab into the uh the asthenosphere the part of the mantle that is below the lithosphere do we have any of those in the pacific northwest i think so i've never actually well yes we have some things like that okay but more common like the one at chemical that's not a basalt so how is that so that's been contaminated by some of this continent no so that's an adakite okay so i know you all right so an etiquette is a rock that looks chemically like the product of melting of the slab okay so in a normal subduction zone you don't melt the slab you melt the mantle right but if it's unusually hot then you can have melting of the slab and unusually hot could be triggered by either you're at the edge of the window where hot mantle is welling up from beneath the slab or if the slab is very young and we have both and we have both yeah we have both we have subduction and there is nothing younger than the edge of a slab window because that's zero age that's that's a spreading ridge in which mantle melting took place magmas rose but they never solidified because it was hot that's why you have you have a window because there was no solidification to make oceanic crust as would be happening offshore so if you're busting on an outcrop someplace you're not you don't know if you have an ada cut right away it just looks like a horse it looks like an andesite yeah or a day site and at what point in your process do you realize it's an adakite that's saying you're at the edge of a window or something after you've analyzed it chemically and what do you see in that analysis element ratios that tell you so we use the ratio of strontium to itrium so two of my favorite elements um and that ratio tells you what minerals were present in the rock that was being melted and so if you're melting the subducting plate one of the minerals that should be in there is garnet and garnet has a very distinctive fingerprint so if you see that fingerprint then we call that an etika the garden wouldn't is it possible the garnet is from some sort of uh rock in the continental crust that the magmas are heating up um it is possible so garnet is forms at higher pressure so if you have thick crust you can get garnet in the lower crust which has nothing to do with subducting slabs just because the crust is thick so you have to be careful yeah when you interpret that but if you're thinking about some place like chumacum which is way out the edge of the large continent that's not a place with this thick crust you've got a place in port townsend do you drive right by this chimney come site all the time yeah what what's a place in the chimichangam area that somebody could visit see this is called chimacam rock or it's also called tomatoes rock it's it's a spectacular monolith it was a sacred site to the indigenous the chemical people it now is overseen it's a a nature area that's overseen by the salaam tribe so it's it's still protected by the local tribe and there's a it's a climbing destination i'm not sure what the rules are about climbing there now but it's a spectacular monolith it has it's a nash flow so what's your guess for the year that you went with there with a couple of students and sampled and what was your motivation to go there well we knew that it was an ada kite already you did yeah i didn't i didn't even know about it uh chimacam rock initially and they were actually out on the road and some guy came down his driveway and said do you know about chumacum rock walk down the next you know take the next path to the left and so there was this magnificent outdrop so that was that was a class project in 2004 i think okay and you got hot on the trail and you started looking for other spots or how about your other your other breadcrumbs kind of in the slab window did you have a general strategy it was mostly a time-based strategy so once the eocene became an interesting time interval then you know look at a geological map see what eocene units are out there so we mostly worked east of the cascades not in the cascades some of both but outcrop is better if you're not in the west side of the cascades yeah so you followed this slab window as far east as where uh northern idaho northern idaho and that's why we are saving that until two weeks from now so you you started visiting between northern idaho and your campus basically and and just started you tried to stay confined to this lab window basically well i actually don't think it's a slab window anymore hello hello so it's it's a it's a rollback story that we'll talk about oh but it's similar and that it's a place where the slab was missing yeah i i some so let's get rid of window but let's let's get the idea that we have to have hot mantle coming shallower than it should be in this pink area correct correct right and and that means that if we're older than 45 million years ago and we're in this wedge we can't have subduction related arc magmas between 45 and 50. i say yeah between 52 and 45 something 52 and 45. so in that interval of time normal subduction was not taking place okay in northeastern washington well i want to do two more things with you i know for sure and then if you've got more time jeff we'll go to some questions from from our live viewers but i i this is breaking news so i got a couple of excellent emails from you yesterday i got a couple i got one email in particular from jamie mcdonald from florida gulf coast university who's been out here working on some of these rocks and you guys have collaborated on a couple of posters or papers or something so between jamie mcdonald and jeff tepper our guest today i kind of had an about face last night and this morning i drew it out so i thought most of these places wait can you still hear me i can hear you so if you're watching in norway this is not going to make a whole lot of sense of course but um i thought many of these places that i keep hearing about and some of our students here at central washington university are from these places like yeah i hike up at pilchuk all the time or mount purses or some of these drunken charlie i don't nobody's talked about that but anyway what i have written out and i don't know how much jeff is going to like this i'm springing this on him but this is between jamie's email and jeff's email i first of all wanted to just kind of potentially group some of these eocene magmas in western washington so we're in the forearc basically but we're in the foothills maybe of the cascades in some places the red numbers are obviously ages and millions of years uh jeff you want to comment on the groupings first of all like you'd well let's see you from your email you said bald mountain and mount pilchuck you thought were were pretty clear in your trench magmas no so what we talked about yesterday so what is what makes this difficult is that yeah at least three different tectonic settings produced magmas in the same place not at the same time essentially in the same place of western washington in this in this general place here so from that place westward as far as the the cascade foothills i guess i would say eastward yep okay eastwood okay so so my criteria for telling them apart is partly geographic and partly age but generally not composition okay so i would so i would say that things very far to the west like you've drawn on the board which would be the etiquites at chumacum or the volcanics those are those are near trench magma type things and those would be associated with a spreading ridge or some other heat source probably has to be a spreading rich a heat source that is underneath the edge of the continent yeah and so those are not all the same age but they're defined they're very different in composition but their geography is the defining criteria as well as what's up in vancouver island right so pretty so those are those are three places that are all at the edge of the continent very different in composition not the same in age but the same in process yeah so those stars along the west there's the ones on vancouver island or towns and the bremerton hills and all those things are way to the west and are probably near trench magmas yeah yeah and and viewers there is a paper waiting for you at nicksettner.com i'll show it i know you know how to get there you go to nicksettner.com you click on eocene and you get to a paper by madsen 2006 and and they they're canadian so they're really showing a bunch of the details up there which again are pretty classic near trench magmas that fit with the most basic version of this story but i guess what i'm getting to with jeff is that he's realizing that and that's about what i think you're about to say jeff that once you get a little bit further east into the foothills you're also getting a little bit younger and therefore it's more of an early days of a cascade arc it's two things that's the that's the challenge so the rollback story that we'll talk about later yeah was associated with ultimately break off of the slab as was as you showed in the in the cartoon of india colliding with asia yeah so that break off also is another opportunity because you've broken the subducting plate as an opportunity for a hot mantle to come welling upward and you can get another you get a linear chain of igneous activity so i think that's happening and that's what i would attribute bald mountain and mount pilchuck too okay so so things that are in the sort of 51 to 48 million year time window those are too old to be part of the modern cascades yeah they're kind of far inland to be near trench magmas right but they define a linear belt that comes from down by uh rainier up as far as mount pilchuck and bald mountain so i make i attribute those to break off of the slab after the accretion of celezia do you i'll put you on the spot do you like any of these correlations between volcanic center and uh plutonic magnet system feeding it which do you like i like hanson lake and granite falls okay but see those are similar in age whereas bald mountain and pilchuck are older right and those and pilchuck and bald mountain are also they're different in terms of their mineralogy they look like a different source of magma okay okay and then i'm i'm quite happy with young's creek uh i don't know much about trump and charlie i mean i've heard of it but i don't i've never been there we don't talk about him at family reunions by the way he's in the corner but yeah those being feeders from mount purses is fine and those i would associate with the beginning of the cascades okay yeah this this this is just what i was hoping for but it's also my fault for trying to shoehorn us into this this uh part of the story because it all kind of flows together i'm starting to realize as i'm talking to you so some that watched the geology 351 sessions last spring you know about jeff's other part of this story where we break a plate twice we have a roll back of a plate and that's all happening in this area where we have this unusually hot mantle surging but we're going to we need to do some i'll say it we need to do some tomography before we get to that so we're going to be getting into some crazy uh geophysics uh before we visit with jeff again um i would add one thing i learned please at the beginning of class today so when you were talking about the distinction between the cretaceous flare-up and the eocene flare-up and posing the question are these different and you pointed out that the cretaceous event is associated with compression whereas the e is seen as with extension i think two other things you could note that are different good one is is the great width of activity in the eocene extending all the way into montana whereas the cretaceous event seems to be much less broad in terms of distance inboard from the margin you're thinking of plutons cretaceous plutons i'm thinking of the ones in that time window yeah they don't extend as far well i guess unless you want to include the idaho bath lift and things but in terms of the ones that seem to be the focus of the dream team project they don't yeah they don't go nearly as far and then just the overall distance inboard so the north cascades plutons are much closer to the edge of the continent where you'd expect to find subduction related activity whereas the eocene rocks are unusually far inboard and harder to attribute to subduction so there's there's some compositional differences maybe but there's also geographic differences i like that i like that was there another difference or that was the main thing well those are the two that i put stars yes yeah the other ones you mentioned just you know compression or transpression versus transtension that's another one and you're also a huge uh crust thickness person as far as um i know this has come up with you even within the eocene maybe that when we're if we have a spreading ridge beneath the pacific northwest we are actively thickening the crust in the eocene we're thinning the crust in the eocene was there any thickening though there was earlier in the cretaceous there was thickening okay and the aoc in there is thinning okay associated with extension so you know of no um like while we're accreting celezia you know of no plutons from the actual accretion is that even a dumb question like no um i would say that there are plutons that are the same age as the accretion but that doesn't mean that they're a consequence of crustal thickening right right good um okay top of the hour we have uh more than about 900 watching let's do some backcountry gary's with us thanks gary for being with us and yvonne on a bunch of familiar names i assume you can't see any of these uh questions scrolling by jeff um maybe i'm i'm on a different my own i'm on a different platform than you are me okay i can see i think i can see them well um it's your call jeff on how you want to operate i typically just sometimes they they go by so fast veteran viewers you know that when you want to ask a question right now please caps lock uppercase and it'll be easier for me to see your questions and i'll just okay well i see why i see one like how do goebbel and northcraft fit into this oh yeah yeah yeah so those are two volcanic units in southwest washington the north craft is now i think the oldest dated expression of the modern arc so nick was saying at the beginning that we've pushed the age for the beginning of the cascades back to 45 million and that's because of dates on the north craft so michael pollins and company who are the the geologists for washington geological survey who map quads every summer have done some dating of that and that's where those came from and the global is another huge volcanic pile in southwest washington which has not really been worked on a lot i think that is also the beginning of the cascades but there's sort of two units there and the lower one doesn't look much like an arc so that actually might record the transition from something that's prior to the modern arc to the inception of the ark so i actually have some samples that were sent off to be dated and we'll see if what they come back to be but both of those i would say are are more related to the beginning of the cascades than they are to any of the other processes we've talked about well i i feel like i want to ask the same question that feels like i'm asking every time i talk to you but like how are you so sure that it's cascade versus not cascade it's not a chemistry difference or it is well so for that there are sort of three criteria where is it yep how old is it right and what is its composition so the cascades being subduction zone magmas have a characteristic suite of geochemical fingerprints what makes that slightly challenging is that if you say go to eastern washington where there has been a very long history of subduction in the northwest so there are old subduction related rocks there if those are re-melted by a later event oh my god you will inherit that subduction seasoning so i like that so it you know it looks taste smells like an arc rock but it's not it's a so that's where the the age and the location and something in the case of the eocene the association with extension and other things that don't look like subduction help you to sort out that although the hand sample or in chemistry it looks like it's subduction related it probably isn't and i guess i want to ask one other thing before we go back to the viewers sorry viewers i'm honking you're hugging your time again yeah someone said the chemical flavor of subduction lingers for a while that is totally true i like that yeah um if you've got something that clearly is not subduction related are we sure it's a spreading ridge underneath there or can it just be the mantle plume itself well mantleplume has a distinctive set of traits so we we should be able to tell that from from a mid-normal mid-ocean ridge okay so one of the reasons that we think that celestia was formed by the yellowstone hot spot being parked under a spreading ridge is that there's a combination of those two sets of characteristics sort of intermingled so you couldn't really explain celestia solely by a spreading ridge but you also probably could hardly have a harder time explaining it solely by a hot spot so those those are two flavors of of lavas that show up in an ocean setting away from a continent but there you can tell them apart but to follow up with that i'm sorry i gotta ask it so we're out of washington now and maybe you're not feeling comfortable but down in oregon i guess i've been teaching that the yahats and the silets and all that are that's north america going right back over the mantle plume at a younger time that can't be spreading ridge that far south well so no so spreading ridge spreading ridges can have offsets on them yeah so if you if you draw a spreading ridge and then have it step to the south transform you can have you can have a new spreading ridge intersection point to the south so you sort of keep reefs up overall the pacific plates are moving northward relative to north america so a spreading ridge intersection slab windows should move northward up the coast over time but every time you have a transformer you can reset it jump it back to the south again so i think there's there's been a fair bit of that which is kind of necessary to keep the ridge parked in the northwest but if you didn't have some kind of resets it would have migrated into canada yeah well that that's what we're going to hit pretty hard on your return your triumphant return uh to the series uh in mid-january where you've got these offsets on your ridge and celestia and everything else and the rollback but i i gotta confess to you that this migrating uh triple junction essentially where the spreading ridge is is subducting that's appealing to me and i want to continue to to think about that and um so i'll leave that alone i'm hugging i'm hugging the time you're always so great at answering these questions thank you do you have another one or should i grab a couple no you can grab okay uh geneva says what are the geochemical fingerprints of a mantle plume they're mostly isotopic so the powerful thing about an isotope ratio is that it's inherited from whatever was melted and it's not affected by crystallizing or the amount of melting or anything else so i the analogy i've used in class is that if you melt chocolate ice cream you get melted chocolate ice cream it doesn't change flavor whereas when a magma crystallizes the elements that are there is its amount of iron or its amount of magnesium those things change so you you don't as i see what was in the in the initial melting event yeah so when you melt deeper inside the earth you get magmas that are isotopically different from the ones that are melted shallower and hot spots and plumes are tapping into this deeper place so they don't look the same isotopically as a mid-ocean ridge basalt which is melting a shallow place and in the big in the big picture of cool you know planetary scale stories i think many people would would buy into the idea that the reason that hot spots are isotopically different is because they are sampling crust that was long ago subducted and is now coming back up again on a sort of 200 300 million year cycle wow that's a mind blower so yeah well related to that the device 9 says are we ignoring the hot spot in the room and you and you're saying yellowstone yeah so you're saying that we don't see those signatures and a lot of these a lot of these guys correct interesting um in part because those guys aren't come they're not coming from the mantle all those those are crustal melting things so we don't see very clearly what was coming from deeper below the crust but well says these are so those are basalts so those those are coming from directly from the mantle and those give us then a window into what was what part of the mantle was melting but if we stray into andesites and things that are not directly come from the mantle then we lose our window yes i'm scrolling back in time and i'm seeing a bunch are asking kind of what we're talking about right now bob uh asked how the tillamook magma is part of the near trench magmas and we're saying no yeah the tone book i would say is attila is one of these things that is younger than celestia so they're basalts right but they were erupted after the accretion was over well that's what i was trying to say earlier that yes uh we we know tillamook and i think yahats and another one i can't remember uh they're like what mid 30s or 40s or whatever right and isn't ray saying that's because celezi was added and then celestia is now riding in the front right north america and going right back over but it's going over a hot spot not a not an ocean ridge it's going over this by that point i think it's kind of a diffuse so there's a there's the center of the hot spot and that's going to be the purest right flavor signature right but then toward the margins of that it's incorporating shallower mantle and it becomes a more diffuse or less concentrated signal so it becomes hard to to see the plume component of the hot spot component so i think those rocks have some of that component but not as strongly as earlier on because where it's where their relationship to the local center of the plume is offset more this is fun uh how about a few more uh go ahead if you got one uh that was scrolled fast something about medicine lake madison lake is a shield volcano yes and it's it's part of the cascade so it's it's fairly young yeah you choose i'm editing like i want to save some of this for january 19th or whatever the hell it is when you come back i shouldn't have set it up this way probably actually you know what jeff let's let's um let's tease your return appearance so i um for the next three shows we're going to be looking at the earth's interior and looking at ocean plates that have subducted and we can find them down there and do some kind of restorations okay that's going to be challenging but that's not your game but i think it's important to do that because then we are going to come back to you and essentially go east of the cascades and follow you don't want to call it a slab window what do you want to call it what [Music] an anomalously hot area i know i'm gonna so i'm gonna say that each of those lines you drew is the edge of a slab window one was to the south and one was went to the north so a slab window is sort of like a zipper that separates if you think of the subducting plate as having segments that are separated by slab windows a slab window allows one portion of the plates to move since they roll back independently of the one to the adjacent to it north or south so on your diagram i would say that rather than having the two lines converge at the margin i'd have them be more sort of parallel to one another and then each yeah so those are those are each these are two different slab windows the one to the south would be the oh oh okay seriously this is yeah the one to the south is is probably the farallon resurrection ridge or window and the one to the north is the resurrection cooler you can't see that and the orientation of the resurrection is probably quite different than you've drawn but the the main idea here is that in between those two windows in between those two windows is eastern washington and we're all that's where all the chalice action is happening well including the north cascades right the north cascades is farther west but it would it would be in that yes so i mean as i mentioned at the beginning of this session i'm always trying to bring things back to the north cascades and you haven't necessarily directly sampled or maybe you have in the united states nothing that you've talked about today okay except the golden horn golden horn you have okay um so we'll we'll i might see if we can explore your story in two weeks and how it might fit in with what we know and what we don't know about those plutons in the north cascades that are eocene in age but regardless your story is amazing as it is and we need that tomography background and so that's i think why the layout of this might work and i think you're one of your next guests will talk about the resurrection plate and i think that will be really helpful i think you're right uh anything else that you grabbed your eye i feel like i want to ask one more of these guys questions i'm coming down to live now uh i don't understand this question i'm going to read it anyway marin says does the plume-induced subduction initiation model fit into this so i actually i don't really care for that model what is it what is the model well the challenge is that we need to after this if after the collision of celestia the subduction zone needs to shift from being on the east side of the olympics to the west side okay okay so for in order for the olympics to be accreted they were riding on a plate and the subduction zone must have been to the east after they're accreted the subduction zone is to the west okay and the question is how do you let's just say jumping first how does the subduction zone jump okay i've been guilty of that yeah okay so one of the challenges in this case is that the oceanic crust is very young and very hot because we're right next to a spreading ridge and if it's young and hot it it's not really subductible you can't you can't easily initiate a subduction zone if the subducting oceanic plate is young so one idea has been presented is that the plume presence of the plume weakened the subducting plate and allowed it to somehow adjust its position i have a different idea in which we move an already subducting portion of the barylon plate which is under california but it's all moving northward over time that it just gradually moves in from the south yeah and you don't really need to initiate new subduction you just move an existing subduction system northward well we're back to it we're back to migrating triple junctions and that's a big part of it for me especially since i'm associated with mike eddy who has kind of an aggressive grain view of this which we'll save for another session but i want to explore that kind of stuff the best i can hey you were great as always thank you thank you for your time and uh you mean it you'll come back in a couple weeks in time i learned a lot every time okay all right all right jeff have a good afternoon thank you thanks nick we'll see you next time okay sounds great bye-bye jeff tepper university puget sound in the tacoma area he's a university of washington graduate did his phd there in the cascades and then has kind of discovered this eocene world during the last 20 years during his teaching career and i met jeff just for the first time a few years ago and immediately thought this guy's different and he's got a lot of interesting work going on with his students and we didn't get into it that much with him directly but he's been so busy teaching his students in these class projects and these independent senior theses and that sort of thing that he hasn't published big papers like some of our other guests and so much of his work i find very interesting but it's really not out there and he's hoping to finally write a couple of these big papers and get it out there but i think at one point i said what do people think about your ideas don't you get a bunch of pushback he's like i haven't written the papers yet they don't even know what i'm do what i'm talking about so we're a little uh i guess premature or it's a little sneak peek into some work that jeff is hopefully going to be publishing in the next couple of years let's do a couple more let's see did i have any more in the ipad no i don't think i did let's do a few more questions that maybe i can handle i don't know if that's possible but um yeah let's do a few more just you and i and then we can sign off for today uppercase as usual i'll scroll back in the meantime and just see if i can grab a couple oh lots of thank you jeffs ooh you like that good um yeah part of this is my fault i think you're wanting to make connections between chalice magmas and the yucate the yakitat or tell me more about eastern washington and how far east did those chalice magmas go i kind of i think you got the sense of that during the conversation i kind of put some borders or some hard edges on our discussion and i did a little back and forth with jeff over the break saying how am i going to take your work and fit it into one show and i realized i just couldn't do it so this slab roll back and uh breaking of ocean plates is very exciting to me and potentially very helpful to the pacific northwest eocene story and there's just not a natural break haha place to break that from this discussion so what i'm trying to say is some of your questions are excellent questions but i'm purposely not going there now and it's coming back uh later sorry patrick i must have said something terrible what else is new i'm way back now trevor why do near trench magmas stop flores mount washington that's up on vancouver island cooler resurrection fairlawn play triple junction okay we're getting there baby we're getting there trevor the next couple sessions i think will work for you we have some experts that will be with us clive could the spreading ridge and the hot spot come close to each other yeah i i i may be off base with this but i i think pretty much any model i've seen has the mantle plume at a spreading ridge like the yellowstone mantle plume is at a major spreading ridge now i gotta say this surprised me i i had the scale totally wrong i had to scale totally wrong with jeff's story of rollback again we're premature with this but i'll just save it but i didn't realize it was such a small store uh the scale of it was much smaller than i thought anyway i don't know if this part is super helpful as usual many of you guys are way ahead of me like i haven't learned it yet okay down to live kevin can you discuss a little deeper a resurrection zone that's coming a week from today why couldn't the magmas inboard of rengelia and celezi be part of prior rifting that's kind of what i'm wondering ken let's let's finish with something that's meaningful to me at least this is how we'll finish today this will work this will work oh this one no wait wait yeah this one well you remember this is the north cascades and the three generations of magma flare-ups and i'm going to eventually come back and hopefully visit each of these and maybe backcountry gary has more photos from us from each of these of course we were in this time window today but these are plutons that are in eastern washington northeastern washington they're not near trench magmas but the question that just came in kent i think it was i mean i i'm not trying to lead us to a place that i know anything about honestly i'm just you know listen i just killed the power takeoff shaft on manure spreader all right i just came in the house just to get warmed up i'm just asking questions that's all i'm doing we obviously know way more about this story which is roughly 50 million years ago cretaceous fireworks and hopefully from today's message you realize that this is an extensional story where these magmas are coming up in something called a slab window even though jeff doesn't like that label in the most basic sense yeah from the madison paper we're talking about all sorts of mantle upwelling triggered melting in the lower crust and having these freaky etikites and other kinds of weird magmas coming up per luminous granites i don't know what i'm talking about but we clearly have essentially this hole we have this place where the crust is thin and these weird magmas are coming up and taking advantage of this window what i think i'm asking is is there any of that story down here if we have a huge in mike eddie's word very voluminous magmatic flare-up in the eocene in the north cascades is it possible some of these big boys and big girls are also from some sort of slab window and some sort of subducting spreading ridge 100 million years ago and you're like well i don't think so well first of all we're twice as far back and you know in geology the more recent we get the more we know there's just more stuff that's still with us it hasn't been eroded or sent back into the mantle or whatever and we're saving baja bc till next winter but what's potentially a major thing that's happened between this and this yeah you take a bunch of rain galley that was docked and you move it almost 2 000 miles is it possible some of these magmas that are today cretaceous in the north cascades we're south of the border the mexican border and if that's true why couldn't we have a spreading ridge down there i'm just asking we're just playing with it we're just playing with it ted irving a toast to you here's to you for returning to the live stream series called that crazy eocene a to z here's to your health in the new year after all the changes to your routines over the last two weeks some of us really look forward to a change in the routine and spending time with friends and family others it's very stressful to be out of your routine so wherever you fall on that spectrum i hope everything's going well for you and everyone in your community here's to our guest today dr jeff tepper from university of puget sound did a great job jeff thank you for your time i thank you for joining us today our next session will be this saturday at 9 00 a.m pacific time the winter quarter has begun oh i can see it's really snowing outside all right um so you know there's plenty going on students in 101 advising students other things and i simply mentioned that in addition to that which is my day job essentially i really enjoy putting these little programs together and the fact that you're on the other end of the line watching these whether it's live or in replay it's just very satisfying and occasionally i'll get asked why am i doing this and it's like i just enjoy it it's just satisfying that's it that's the end of the story it's just fun to put this stuff together and then get it out there and then move on to the next thing so thank you for being with us today and always with these shows all right we're done for today i'll see you saturday morning at 9 00 a.m pacific thank you i love you and goodbye from ellensburg washington usa goodbye

Channel: Nick Zentner

Views: 15,267

Keywords: Nick Zentner, Crazy Eocene A to Z, near trench magmas, triple junction, Jeff Tepper, Chimakum Rock

Id: x_c_izaMWjk

Length: 107min 34sec (6454 seconds)

Published: Wed Jan 05 2022