Mount Rainier Geology

we're going to start with some plate tectonic lessons in fact I had a couple of emails this past week with some follow-up plate tectonic questions from last week so we'll go ahead and start there and help us understand the Cascades itself let's start with kind of a review I suppose if you've been with us a number of times let's see how I'm going to do this yeah right that's the plan I'm going to do this so we should probably need some music here I suppose too while I'm while I'm drawing I want to draw a plate tectonic cross-section let's put a boat in here let's put north america moving west we know that right this is an underwater mountain range called let me label it properly for you called the East Pacific Rise and those of you that know basics of plate tectonics you've heard maybe about the mid-atlantic ridge which is a an underwater mountain range that was discovered right down the middle of the Atlantic Ocean back in the 1950s and early 1960s which really helped us understand this whole plate tectonic business that was one of the keys to unlocking that whole mystery well the Pacific Ocean has a similar underwater mountain range that is very active meaning that magma is coming to the surface from the asthenosphere and is creating crust on the ocean floor and that crust is spreading away in both directions from that underwater mountain range just like the mid-atlantic ridge in the Atlantic Ocean but this is not the Atlantic right this is the Pacific Ocean and this is this is North America and I put Westport down there which is our coastal community of reference however this is going to be a picture 200 million years ago okay more on that in just a second let me draw the same thing on the white on the chalkboard here now why would I draw the same thing I want to draw the same thing but I want to on map instead of a side view on a draw map of the same view and I'm going to do this and then I'm going to do this okay what is this so this is North America now we're looking down from heaven on to North America moving west and what is this zigzag pattern out here it's the East Pacific Rise the epr and coming away from the East Pacific Rise are these arrows showing what showing movement of the ocean crust move into the ocean floor in both directions and the East Pacific Rise is broken by some San Andreas Fault like faults so these are actually some plate boundaries here separating that okay this is also 200 million years ago now 200 million years ago is famous in the history of our planet because a large supercontinent called Pangea started to split apart 200 million years ago and for the first time North America started moving west and by god north america is still moving west 200 million years later but here's the first message of tonight's lecture the distance between Westport and the East Pacific Rise was a hell of a long way 200 million years ago and now it's not that far in other words the North American plate has been slowly inching closer and closer to this stationary East Pacific Rise over the last 200 million years and why are we talking about this tonight we're talking about it tonight because there is not only earthquakes generated at these subduction zones but there are beautiful cone-shaped volcanoes coming right up from the subducting plate so here's a concept for you these X's are beautiful cone shape volcanoes erupting material Mount Rainier like mountains that are erupting volcanic material we had an intact beautiful chain of volcanoes all along our West coasts 200 million years ago stretching from Alaska down through British Columbia down through the Pacific Northwest continuing all the way down through Mexico beautiful intact chain of active volcanoes 200 million years ago similar to what continent today South America today has a beautiful chain of volcanoes going down the east coast excuse me the west coast those are the Andes right okay so we have the same thing we had an Andes like contend of complete intact chain of volcanoes 200 million years ago okay what are we going to do these diagrams we're going to flash forward to today okay and to do that I'm going to remove 200 million years ago I'm going to remove most of that plate which I didn't label for you but I guess I'll just tell you what the name was in case you're curious it's the name of Farallon plate oh heck I should write it since it's on the test tomorrow I should right there is an exact there is an exam tomorrow in my election in my geology of national parks class I had a lot of visitors to my office this afternoon lots of hand wringing a few tears lots of problems okay so we tried to solve it okay so that fell on plate this dominant plate of the planet 200 million years ago the monster plate has been slowly reduced in size why because we're going to move this boat we're going to move this continent closer and closer to the East Pacific Rise until today we have a more familiar picture the picture that we had on the board the last couple of weeks when talking about earthquakes what do we have here North America here's Westport beautiful penmanship and this is not the Farallon plate anymore what's the name of this plate that's right it's the Juan de Fuca plate so here's a little secret the Juan de Fuca plate is just a new name we have for what's left over of this thing called the Farallon plate in other words the Farallon plate is the ancient plate that is responsible actually for much of the geology of the west coast of North America and this last little piece that's still hanging on and the distance between West port and East Pacific Rise not very much that's what we've got here it's a remnant North America has gotten closer and closer to these specific rise okay I'm going to change this a little bit but I want to do the same thing here I want to draw a picture today oh heck I'll do it over here so let's pretend this is North America now that's moved away oh I should do it we shouldn't pretend I got to do it I got to do a complete job here now notice a couple of things this is today same as what we have over here here's the Juan de Fuca plate coming at us and by the way I'm being coy about these arrows out more on that in a second these are the Cascade Mountains we have 17 active composite cones or cone shape volcanoes that are actively erupting why because the Juan de Fuca plate is nextdoor subducting here's the important point notice that we don't have any X's in Central and Southern California where we used to have them why don't we have those volcanoes anymore the answer is North America has started to cross over the East Pacific Rise the East Pacific Rise further south has literally slipped beneath North America and now we have the Pacific plate moving towards Japan in interaction with the North American plate and the result is the San Andreas Fault so if you've been to the Sierra Nevada mountains in California Yosemite National Park Kings Canyon Sequoia national parks beautiful right that's where the volcanoes used to stand in Eastern California and there has been a complete transfer of power from active volcanism in California to now uplifted mountain range made out of complete granite granite that was actually formed underneath the volcano so the volcanoes of California have been a roof and now this underground magma has solidified and come to the surface why am I getting into this we're talking about Mount Rainier tonight one of the questions that I added on my email to you to try to entice you to come this evening it was creepy one of the question was are we always going to have Mount Rainier on our western horizon on a beautiful Bluebird day like we had today the answer is no and I hope that you can see why this has been a very slow gradual process of destroying the Farallon plate now called the Juan de Fuca plate and the job is not completely done I give it five million more years five million more years if we come back we can magically come back five million years from this evening I'm of the belief that North America will have crossed over the East Pacific Rise here just like it has at points further south and that means our volcanoes Rainier Adams st. Helens Baker Glacier Peak and down further to the South Jefferson Shasta hood lassen they're all going away and taking their place will be magma that is presently underneath those volcanoes solidify the magma bring it to the surface in other words I think we're going to have a Sierra Nevada mountain range to cross between Ellensburg and seattle five six seven million years down the road that's the major way that I teach this to my students in the national parks class because many of the national parks of the American West are tied into this story of North America slowly crossing the East Pacific Rise now the plot thickens slightly before we narrow our focus to Mount Rainier itself Tim Melbourne this guy that I talked a fair amount about yesterday excuse me last Wednesday the guy that was doing the work here at Central involving the silent earthquakes I just casually sent him an email last night and said Tim this is a holdover from last week but I convinced the group last week that that the one de Fuca plate is moving northeast towards Washington and why do we know that we had our we had our GPS stations last week remember going northeast and then turning around suddenly for two weeks and then northeast and that basically the compression from the Juan de Fuca plate is causing a northeasterly trajectory my question to Tim was it's always bugged me why the Juan de Fuca plate is going north east when the spreading out of the East Pacific Rise off of our Shore looks like the Juan de Fuca plate should be going southeast do you see my issue here just the geometry here says isn't the one if you could play going southeast instead of Northeast and he said well first of all you're wrong that's always a nice way to start an email isn't it Nick hi Nick first of all you're wrong so I kind of knew I was wrong but I wanted the full story and I'm not going to go through it because it gets into how the plates are moving with respect to a neighboring plate if all these plates are moving you have vectors of motion and it's hard to pinpoint exactly who's doing what because it's all this relative motion jostling next to its neighbor Tim's basic message was he says that this spreading Center here the East Pacific Rise is not fixed in other words this boundary is not as permanently located as I'm presenting it he says the East Pacific Rise is drifting northwesterly with the Pacific plate in other words the Pacific plate is dragging this plate boundary with it and if you work out the vectors of that and us coming actually southwest that was part of our story last week you can complement the vectors and get a northeasterly direction okay so I have two choices as a teacher right I can pretend I never had the email with Tim and I can continue with what I've just taught you which is what I teach in my 102 class or I can try to get into these different vectors and try to give the real story I'm torn between the two I got I got to be honest with you this is a very simple story and it appears we're making headway on getting rid of the Farallon plate so I'm stubborn right now twelve hours after getting the email to think that that I I might still be right that we're going to get rid of the rest of the Juan de Fuca plate before it's all said and done but if Tim turns out to be right this spreading Ridge is actually going to drift away from us and the Juan de Fuca plate is going to maintain its size hell it might even grow in size if we're taking this Ridge and drifted away from us faster than North America is moving west okay so now we're officially on a tangent how's it feel we're way off track all right students hate that right here's what we're doing today and then I'm off on something else and am I supposed to write this down is this going to be on that you know okay so it's my lecture dammit I'm saying Mount Rainier is going away and with the rest of the Cascades because of us finishing this job okay let's get something a little less controversial and talk about the Cascades themselves so time to look at my notes quick yep that's what we're doing good you know what this is by now this is Washington of course it is let's put Ellensburg in let's put Seattle in let's put the i-90 drive between Seattle and Ellensburg okay I ninety terrific we have five active composite cones in the state of Washington let's put them on the map Mount Baker Glacier Peak Mount Rainier Mount st. Helens not Adams okay we got five we got five mountains that have the possibility of erupting starting tomorrow and with our understanding presently of the Cascade volcanoes all are possible to start rumbling tomorrow and the good news is with these types of volcanoes we usually usually have multiple weeks of small events before something big and that is a comforting thought that it does not appear based on composite cones around the world in the last hundred and fifty years doesn't appear that Rainier is just going to go bang tomorrow at noon with no warning whatsoever we'll get swarms of small earthquakes we'll get changes of the slope of the mountain itself we'll get dramatic heat changes at the top of the volcano glacial melt will start more dramatically we'll have changes in the gases at the summit nodes will have all these small things and if you're a sane person you'll get out of harm's way and the mountain will do its thing okay so how long have we had the Cascades in general the answer is 40 million years how long have the Cascades been in Washington 40 million years now what I mean by Cascades is this corridor of active volcanism but I'm not saying that Mount Rainier has been standing for 40 million years or that Mount Adams has been standing for 40 million years instead this corridor this height this this little ribbon of active volcanism that we call the Cascades have been active for 40 million years why not back to 200 million years that's going back to our first lecture of this series where we're bringing in pieces off the ocean and building Washington it's not till 40 million years ago that we had this be the appropriate place to start sending magma up from the subduction zone okay so 40 million years now here's what I think is really interesting and not as well sold to geology students around the country or spread around Washington if you start digging deep and looking in this corridor between our five active volcanoes it suddenly becomes very clear that we have and I'm not exaggerating now hundreds of old volcanic centers what I'm drawing here in blue X's are inactive cone volcanoes in other words places where Mount Rainier like mountains used to stand used to erupt and lost its magma supply and has been eroded away and then a neighboring cone grows beautiful nice and big erupting material looks like a national park loses its magma supply goes away we literally have a graveyard of volcanoes in the Cascades and there's only five current places where we have volcanoes that are alive Mount Rainier has only been standing at its spot for less than a million years I'll give you an actual number half a million years for Mount Rainier we've had Vulcan we've had volcanoes in western in Central Western Washington for 40 million years our present guys have been there for half a million years or less st. Helens is even less than that so when I say that Mount Rainier is not always going to be on the horizon I mean it I mean forget about the debate about whether the Juan de Fuca plate is going to get destroyed completely or not even with our understanding of this it's pretty safe to say that Rainier is not going to stay that long my number here I'd say the average lifespan for a for a cascade cone volcano is two million years you you have it born you have it nice and beautiful in adolescence it slowly starts to crumble away as we get older it's gone okay that's it a two million year lifespan for a cone in the Cascade corridor and we're a quarter of the way through the life cycle for Mount Rainier these other places our places you know in other words where the blue X is their locations that you might know if you've hiked in the goat rocks if you've hiked up or how to take your pick I don't need to go through take your any favorite place up in the Cascades that's not these five red X's I'll be willing to bet you there's some old igneous rock nearby that's basically the old plumbing system of that volcano the structure is gone but the underground magma has cooled off and we can reconstruct where that magma was there's some researchers still working on these problems Paul Hammond is one of them a retired geologist from Portland State has been working in the Mount akes and goat rocks and other places basically on the way up to White Pass but that's just a local example there's lots and lots of great examples of this so that's something we want to work on and try to understand good on to the next topic some basic stuff and then we'll try to speculate what's coming down the road for for our lecture I've been having an internal debate in my mind as I've been talking the last 10 minutes I don't know if you can tell and I I just I just decided I got to tell you this story okay my office this afternoon one of my freshmen getting ready for the midterm tomorrow she knows that Geographic examples are very important of geologic concepts so if we talk about a divergent plate boundary it's equally important to know a couple of places in the world where they exist so she's a hard worker she's in there in my office hours I give her credit let's call her Julie and Julie opens with this question ah I'm having trouble with Geographic examples where the Cascades all right and I said Julie we can figure this out where are you from Federal Way Julie are you going to go home this weekend yep I go home every weekend you got your own car yep you're going to go over the pass yeah I'm going to go over the pass I'm going to go over those mountains Yeah right Julie are you she wouldn't she wouldn't she wouldn't take the bait so those are the Cascades Julie those are the Cascades that mountain ranges right there you drive over the Cascades every weekend so she wrote it down she's got it now okay let's say you're a composite cone I don't care if you're in the Cascades or in the Andes or in Japan Fuji composite cone Kilimanjaro Africa composite cone I don't care who you are you have the capability of producing four different things when you erupt mr. composite cone and I guess I'm gonna do the same thing I did just before I'm going to do a cross-section of the cone and I want to draw a national park boundary and I want to look down on top of that composite cone okay and since you're not being tested I'm not going to bother writing these names down but I'll just give them to you verbally number one we're going to get a bunch of volcanic ash that's blown downwind and we're going to have that ash fall onto the landscape so I'm going to change my picture so we can actually have an ash column so here's our towering cloud of ash you can think Mount st. Helens in 1980 if you like and then the prevailing wind is going to take our ash downwind and we're going to literally snow that Ash down onto the landscape and create a blanket a layer of ash that's ash fall now let's just presume there's westerlies on that particular day and so we're going to have this cone of area that is to the east of the erupting cone if this is Rainier and this is Rainier National Park this is us friends if we're talking about volcanic hazards it appears that's our likeliest candidate for experiencing Mount Rainier when it erupts an enormous amount I don't know what that means enormous by the way I will talk about that before we quit a lot of ash if we have a westerly is coming across Rainier okay second of all what do you get we're going to have some ash flows not the same as ash fall so ash flow is the most dangerous 100 miles-an-hour white-hot a traveling cloud of ash rock gas logging trucks anything it picks up along the way and this is a ground-hugging cloud that is not deflected by any topography so if there's a ridge in front that ash flow is going right up and over that Ridge and continuing so we're going to basically get our momentum from that oftentimes by the column collapsing on itself and having much of this material literally get a head start before it starts cruising over the land surface you do not want to be in the path of one of these got some video for you in just a bit so that could be any particular trajectory coming away from the composite cone really no good way to predict the direction that that's going and if again if this is Rainier we have ash flow deposits not far outside of the National Park so Ellensburg does not have to really worry in my opinion for ash flow material because of our distance from the cone and because we don't have any pyroclastic flow deposits in Kittitas Valley or ash flow deposits that's the best way to judge volcanic hazards is to look at what's underneath your ranch as it happened before has something gotten to your ranch before boarding Puyallup that's coming in a second so if there's stuff underneath your town from an erupting volcano in the past we're going to increase our chances obviously third of all we're going to have lava flows and most of us think of lava flows coming away from an erupting volcano as being a very hazardous thing but hey these are sticky lava flows with cone volcanoes these are not Hawaiian lava flows that flow for tens of miles or the flows that came across Eastern Washington that's basalt this is andesite this is stickier higher silica Magma's that are more viscous not wanting to travel so again it's a comforting piece of news if you visit rainier park the lava flows are as plain as day when you look at a geologic map in fact if you can visualize in your mind your trips to rainier there's kind of a radiating set of ridges that go away from the mountain itself each of those ridges is an old lava flow that didn't get much further than the park boundary finally mud flows you've most of you have heard this story the mud flows are the real threat to residents of the west side not so much us here on the east side and that fourth one the mud flows were not even really understood until the 1950s and 60s and 1970s and that's part of the video clips that I want to show you tonight some really great work we had real imaginative work from Brian Atwater a couple weeks ago imaginative work for other people the hero tonight is a guy named rocky Crandall who back in the 50s and 60s worked for the US Geological Survey and was the first to kind of be creative enough to see deposits and realize my god these are actually flows of mud traveling tens of miles from the mountain leaving the park and getting down to the Puget Sound many large communities now built on those old mud flows so the good news there for predicting mud flows coming away from the cone are the mud flows are following river valleys so we can predict the paths of those mud flows simply by looking at the drainages coming away from the mountain so here are our active drainages coming away from Rainier again there's good news for Ellensburg the crest of the Cascades the topographic High Point in the Cascades that Julie now knows and has in her notebook is protecting us from even these mostly dreaded volcanic mudflows otherwise known as lahars even these drainages coming directly east towards Ellensburg are the mud flows are going to follow the drainages and eventually head western so we're really in good shape and I might comment while I'm thinking about it we haven't maybe found all of the ash deposits in Kittitas County but I'm guessing that we've run into the major ones and there's really nothing clear connecting the Kittitas Valley with Rainier Park before we go to the slides I want to give you a sense that our main understanding of the history of this mountain is looking for all of the ash Falls from past eruptions all of the old mud flows from past eruptions and we have precious little on this side of the crest from Rainier in fact we have precious little period we've got a famous ash layer down in the canyon that's typically attributed to Mount Mazama down in Southern Oregon we have a beautiful about six inch volcanic ash layer in Craig's Hill right above the fairgrounds that's been studied and it's much older than Rainier it's it's a few million years old unknown which volcano erupted so there's toughest out there there's ash layers out there that just haven't been looked at very carefully that's one of my main messages tonight well there's plenty more to learn about the history and potential eruptions in the Cascades because we haven't had the man-hours invested in all of these ash deposits so for the rest of tonight before we go to the the technology I want to talk about number one and number four the ash fall coming downwind and the lahars or the mud flows coming down the river valleys and I want to give you a sense of what was discovered back in the 60s and how that has changed in the last century excuse me in the last decade how that has changed in the last 10 years and how we've got a better but not complete view of what was has been going on with Rainier through time normally when I teach I like to have a conversation going with the group and we have plenty of back and forth but we're in a well-worn groove right now we want to make sure that we get through what I have planned and then there's plenty of time after the lecture to follow up with questions so let me summarize the best weekend I tried to come up with a creative way to present this and I ran out of creative ideas so I think I'm just going to write a few things on the board for you just to give you a sense for how much we know about the history of erupt effectivity recently with Mount Rainier it's currently active meaning it has magma inside of it the magma is hot there are 30 small earthquakes per year with Mount Saint Helen excuse me with Mount Rainier 30 quakes annually with small a small motion of magma within the magma system there's continual heat transfer to the top of that mountain in fact if you've ever been to the top of Rainier I haven't but if you have if you've seen photos there's some beautiful summit craters and the rims of those craters are snowless you know that most of Rainier has thick cover of glacial ice but even after a big blizzard a few days later that snow is gone up at the summit craters because of the heat coming off of that radiator so it's a throbbing heat filled structure there's no question about if it's going to erupt based on the history I'm about to give you so I'm going to put his name on the board rocky Crandall Dwight I think was his given name to white Crandall and another guy Mullen I forget his first name pardon me for that back in the 50s and 60s they did the groundbreaking work on looking for ashfall deposits and lahar deposits from Rainier this is all Rainier now in Rainier Park they dug a famous trench right next to the sunrise Visitor Center been up to sunrise okay you can picture those beautiful parks that are up there okay I've got one slide in particular that shows the the just one simple ditch that they dug one hole that they dug looking for in ash flow deposits from Rainier and they got ash Falls that they could date you take some of the ash you send it to a lab they do some absolute age dating and they come up with a numerical date for that particular ash 18:40 ad 14 79 AD 190 BC 500 BC 700 BC 15 BS I disrupt BS it might be BS 1500 BC 3600 BC I'm not going to go on forever I want to give you some of these landmark ash deposits two four six eight nine I think there were ten classically found ash fall deposits at sunrise right there on the Mount and they weren't hard to find you know how science works right the first time you look you find the most obvious things then somebody else comes in and they find the less obvious things these were actually given letters so in the literature there's actually letters corresponding to these particular ash layers the letters correspond to the locations that they were found now this looks like a history of Rainier we're in Rainier Park right we're finding ash deposits in Rainier Park it must be reading your ash it's not all Rainier ash so not only can you get ages u can get chemistry of the ashes and you can match chemistry's in other words you can find this ash layer and say does this chemistry of this ass match rhaenyra's chemistry or does it match st. Helens so let me add that Rainier st. Helens Rainier Rainier st. Helens st. Helens Rainier Mazama the famous crater lake explosion of 3600 BC oh sorry I'm off uh-huh uh-huh Rainier Mazama and Rainier this will play real well on TV by the way okay great then hell is just next door we get a significant st. Helens eruption we're going to blank it right near with ash I never thought about that till I started reading some of this stuff so I'm not asking you like we did with the Chris Goldfinger lecture to look at the average number of years between ash layers and come up with a recurrence interval that's what we did with those underwater landslides if you recall why am I not doing that here because this is just the 10 most obvious ash layers the work that's been done in the last two decades by some other folks Tom Sisson few other guys Jim Vallance some other folks I haven't met Pat Pringle I'll just cut to the chase they now have 40 so here we're 10 ash layers in Rainier Park not all of them from Rainier there are now 40 clear ash layers with ages most of them attributed to Rainiers eruptive history and maybe more importantly for us the kind of take-home message from that as we have 12 Rainier ashes since 500 BC that's a more accurate representation of the last 2,500 years and if that's a complete wrap-up representation maybe we can start doing recurrence interval talk a little early for that though probably while we're doing this let me give you a few more and then we'll go to the visuals because then it just becomes me listing stuff up here which is not that fun this is all ash these are all fine layers of ash blown downwind and deposit it snowed on the landscape lahars remember are different I'll have some video for you but to prime you for this lahars are the result of a flank of the mountain moving landslides convert that into a flow of debris so we have a side of the mountain that has what glacial ice it has snow it has water it has rock it had a has lava flows it's got a visitor center on people I don't know let's not put that in there okay and then we have this event maybe an earthquake triggers the mud flow doesn't have to be an eruption but most commonly it's an eruption that triggers a failure of the flank of the mountain and we have that material have so much moisture in it so much water in it that we can actually convert that landslide into a flow and have that material start sailing down a river valley the consistency of concrete wet concrete stuff in a cement mixer 40 miles an hour 30 miles an hour coming down a river valley at you it's a hazard it's a problem many of you know many of you know of the hallmark the most famous mudflow probably in the world but at least in North American geology involving Mount Rainier the Osceola mud flow date 3600 BC ten times bigger than any other lahar deposit in the Pacific Northwest so this was a monster it actually reduced the summit of Rainier by more than a thousand feet so Rainier used to be taller by extra thousand feet so the top part of Rainier converts into one of these flank landslides and the scar is still at the summit of Rainier I'll show you in a second how to find that how to look for it that's the mud flow that eventually got to Tacoma and that's the mud flow but Tacoma Auburn Puyallup ording are built upon and there is real concern of a repeat performance because the mountain has rebuilt itself and there's some real cause for concern I'll let the video speak to that that was a probably rocky krandalls claimed single claim to fame visualizing that that deposit was a mud flow realizing that it was this coherent event that happened at this time there are some lesser-known mud flows or lahars including the electron mud flow that happened about 500 years ago we now have again with current work that's the theme we're working on with this spring now this is fall that's that that's the theme we're having this fall current work adding to known stuff we now have 50 lahars 50 low hard deposits from Rainier that have been found and have been mapped out unclear to me if the ages have been assigned to all of those yet but we have at least seven lahars since Mazama since the crater lake explosion we have clear evidence of seven lahar sitting on top of that Mazama event simple picture to start with many of you have seen this before subduction zone fuelling magma into our system here go ahead er when we cool the magma off underground that's our granite formation we get the magma to the surface and have an erupting volcano that's andesite and Marty I'm saying that as soon as we have North America across the mountain range that sending stuff are away there is no more stuff coming our way so we're going to take get rid of this subducting plate and the subducting plate is the only reason we have volcanoes to begin with next one Eric okay here's a map of the East Pacific Rise can you find it there's North America South America and right here is still the East Pacific Rise but notice where it goes right into the Gulf of California and disappears next one Eric East Pacific Rise disappears we've crossed it except for a little piece of it right out here that's our own special little East Pacific Rise making our own little Juan de Fuca plate notice South America still has all of its volcanoes because it isn't even close to crossing the specific rise so this was us back 40 million years ago now this is us today crossing the finish line like a the end of a hundred meter dash we're crossing the tape next one so down to California what does it look like here's here's us and our active volcanoes here's the Sierras Nevada range where the volcanoes used to stand why don't they get volcanoes anymore there's no more subduction this is the Pacific plate heading toward Japan fueling Fuji and so next one Eric if we go to the Sierras it's all granted the volcanoes were here they're up in heaven literally they're gone and even Half Dome and Semmy Park is granite magma cooled underground next one please here's an animation showing North America crossing the East Pacific Rise and getting rid of a volcanoes this is the last 40 million years of time some of you have seen this one before let her roll baby there we go okay so this video she looks like that the East Pacific Rise is moving towards us but what's really happening is North America is crossing over the East Pacific Rise and notice here's our Juan de Fuca plate and actually I'm curious to see how they're showing these specific yeah they are seeing it well okay whatever Tim's right Tim's right okay next one all right here's the one if you can ridge here's our small little plate notice that the north-south distance of these little slabs of what's left over from the Farallon controls the north-south distance of these cones you get south of lassen comb there's no more volcanoes because there's no more ocean crust coming at us the yellow are the old cascade deposit in other words the graveyard I was talking about let's look at that a little bit next one so here's Hood Adams st. Helens Rainier Glacier Peak and all this light green are older volcanic deposits where the old volcanoes used to stand next one same message this is from an excellent book cranked out two years ago by Pat Pringle it's the roadside geology guide to Mount Rainier National Park it's a spiral-bound thing if you've used a roadside geology book before you know it's kind of fun in a weird nerdy sort of way I recommend this this is this is two years ago there's a lot on here can I can I convince you what what the main message is here's Rainier here's st. Helens here's Adams and all these colors old volcanic centers again these are places where cones used to stand but have crumbled away we've mapped them and I've identified them by age everybody's less than 40 million here pretty spectacular next one ah so I have a way to tell my students how this works you've got the Cascades for 40 million years but you don't have actual standing volcanoes for 40 million years we only have a two million year lifespan right so this is at the county fair game called whack-a-mole and so you whack one mole and you think you've got it but then another mole comes up and then you whack that mole and two more come up and then you whack those and two more come up that's the history of the caste gage next one whack them all that comes another cone up next door next one whack Amole laughter we've got rid of these vote here comes another one two million years boom two million years boom you got it okay next one please so terrain here we go from Tacoma looking south east next one please yeah the insides of these cones are complicated they're not all lava flow layers because of those four possibilities we talked about ash fall ash flow lava flow mud flow the combination of things so the next one is an animation showing some of these in action and kind of an animated cartoonish way next one Eric oh sorry it's not here's just a chart showing that Rainier got it start 500,000 years ago and the whole structure has built just in that last five hundred thousand years next one please I don't know where that movie is maybe I took it out here's Pringles roadside book highly recommended I can help you later on if you want to find it next one please there's Pat himself fine fellow and Bob Butler is included he was one of the main paleomagnetic guys who didn't like the Baja BC story that we've told on our first lecture next one please here's an interesting chart that you may have seen before each of our 17 cones in the Cascades and our current understanding of how often they have been active in the last 4,000 years so st. helens has been very very active what is this based upon ask you know ash Falls lahars the things we were just talking about and to be honest my gut feeling is Jefferson for instance is naked here Adams only one I don't think they've been that quiet personally we just haven't found the deposits yet that's my take but as our current understanding this is the way we view the history of all 17 of those cones they're all being fueled by the Juan de Fuca plate subducting next one here's that movie let's play a Turk stratovolcanoes are built from alternating layers of pumice and ash or lava produced by many different abruption x' over tens to hundreds of thousands of years the volumes of individual Russians can be small to large the Magma's have moderate to high viscosity x' but a range of gas contents gas rich Magma's commonly blasts high into the atmosphere pumice and ash ball from the eruption cloud adding a new layer to the cone itself and blanketing the surrounding landscape Magma's with low gas contents produce lava flows some lavas erupt from flank bends other lava flows erupt from the summit crater because the lavas are fairly viscous they don't flow easily tending to perch on the sides of the cone and helping to give stratovolcanoes they're relatively steep profiles the most dangerous types of explosive eruptions are those that generate pyroclastic flows the ejected pumice and ash fall back around the edges of the eruption column and feed hot clouds of pumice ash and gas that move rapidly down canyons on the volcano's flanks and speeds of up to a hundred kilometers per hour when most people think of a volcano they envision a stratovolcano well known examples are Mount Fuji in Japan and Mount Rainier in Washington State ok so if we take a peek in the flanks of Rainier we're now up climbing or using helicopters get up on Rainier itself and looking at the rock exposed between glaciers we're seeing it's not account is not a simple story it's quite complicated next one please and I want you to just notice that there's a variety of looking things in here not all the same stuff because of these different products next one here's a person standing next to a particularly ashy layer and then here's more maybe an ash flow tough for one of those ash flow deposits coming on so the history is laid out there for us we just have to look at it and read it properly next one here's some Thompson's slides I find this particularly cool that there's a huge pumice layer from one hundred ninety five thousand years ago making up the wall so sometimes these layers just hit you over the head other times you have to work very very hard to find them at the flanks of the mountain next one please I got a few more slides here I've got eight o'clock I heard a couple beeps your watch is going off you got ten more minutes okay let's go for it so keep it going buddy all right so this is not Mount Rainier this is in the tropics somewhere concern in in the park not concerned for Seattle not concerned for Ellensburg these are this is ash flow coming right out at you next one please okay more on Rainier itself next one please here's a nice shot looking at ording the Carbon River the Puyallup River and Rainier what makes up this valley floor mud flow this is the main contribution back in the 1950s and 60s from Crandall next one please so the lahars as we mentioned are often converted landslides although sometimes it can literally be mobilized material coming from an erupting column but the point is it's a slurry of water and rock that has potential danger as well next one please so here's a video clip of rocky Crandall himself I think he passed away recently unfortunately but this is from a DVD that's now out of print called perilous Beauty I think it was cranked out in 96 next go ahead and let's activate this but most important to us are the sudden landslides that every now and then tear away vast portions of the cone and send massive mud flows thundering down its valleys many have traveled tens of miles all the way to the Puget Sound lowland development is now crowding into these same valleys building atop the remains of old mud flows what events might affect these towns over the next 50 100 or even 500 years rocki Crandall began to answer this question quite unexpectedly during a study that began some 30 miles from the mountain on the edge of the Puget Sound lowland I was at just out of graduate school in the early 1950s and I was assigned by the Geological Survey to make a geological map of an area east of Tacoma Washington working from older maps Crandall expected to find the hummocky remains of glacial deposits around the towns of Buckley and enumclaw when he arrived he found only a flat plain where he expected to find glacial sediments plastered on the hills they seemed to occur only in the valleys as Crandall attempted to explain how the valley floor had formed he found himself moving in a surprising direction and toward a stunning conclusion and I came up with the idea that perhaps it had actually flowed into place like a giant mud flow and it's just like a light going on over my head because everything I knew about the deposit that this kind of an origin that had actually in flowed into place it had not been formed by a glacier at all but the question in my mind is if it isn't mud flow how how did it ever get started where did it come from and I had no idea at all even though standing there on the plane that was formed by this much though I could see him over near the distance and I didn't make the connection for a long time as Crandall searched vainly for the source of this giant mud flow known as the Osceola its deposits led him up the white river to a point 10,000 feet up the northeast side of Mount Rainier so we could hardly believe our eyes would we actually find a remnant of the same deposit there at the tip of Steamboat route as he stood on steamboat prow looking toward the summit Crandall realized that the Osceola could have come only from the southern : ups of a major segment of the mountain this was a radical idea such massive volcanic landslides were virtually unknown that is until 1980 when the North flank of Mount st. Helens weakened by rising magma collapsed in the largest landslide ever witnessed the landslide released an explosive blast that laid waste to over 200 square miles of forest and the landslide also spawned a giant mud flow that raged 50 miles all the way to the Columbia River when all had settled Mount st. Helens lay gutted and bear the upper tutor river had become a barren and rocky place where craggy fragments of the mountain popped the surface of the landslide here's our yellow areas where most of this is the Osceola all these areas here is where the Osceola actually hit and got into the Puget Sound right there Tacoma find pieces of Mount Rainier literally in downtown Tacoma in part of this slide that was a major contribution by by dr. Crandall next one please okay these are kind of odd oh no they're not so here's the old rim basically the scar from the Osceola in other words that upper part of Rainier converted into a landslide and flowed and here's the scar that was left can we find that in photos keep it going here Eric great that's out of order there's the scar we now know that the entire summit and North East face of Mount Rainier fell away suddenly in an immense landslide accompanied by volcanic explosions the landslide became a mud flow that filled the White River Canyon with up to 600 feet of rock clay water and ice this cement like slurry thundered down the valley at speeds up to 50 miles per hour as the flow left the mountains it spread out to form the enumclaw plane that had led to rocky krandalls original insight finally the Osceola disappeared into Puget Sound it is difficult to grasp the destructive force of one of these massive mud flows great so here's our scar here's lava that has grown since the Osceola so in other words Rainier has rebuilt itself almost completely and here's the former summit before we slid that material away here's another triad it Eric used to be a bigger mountain and after the Osceola was significantly shorter than we've had the lava dome growth since few Lauren were done another shot same thing looks like a big scoop ice cream that's glacial ice that's on top of a rebuilt andesite lava dome in the 5000 years since this event keep it going Eric here's what a lahar de Osceola actually looks like so that's what a mudflow deposit looks like after it comes to rest next one st. Helens we're talking about Ashna oh I got to get to these sorry about this this is running a little longer than I wanted go for it so here's Jim look at all these ash deposits age for each of these ashes some of them Rainier some of them st. Helens some of the Mazama next one so here's Rocky's pit right at sunrise each of these letters corresponding to a particular eruption here o is Mazama same Mazama we have in the south part of a Yakima River Canyon and each of these guys set up beautifully next one as we get farther away from the mountain the the particle size decreases you can imagine that right as you transport it longer you're going to have finer materials out so we can even work with the size of the particles to make a basic call as to how close we are to the ancient mountain even if the mountains gone like Craig's Hill for instance we've got our ash in Craig's Hill but that's too old to have a present volcano standing next one know where that is right Yakima River Canyon Mazama ash there's some other ashes in there as well there's still some debate about the significance of those to my knowledge the only significant ash deposits in the central part of the county next one older sites also in the park this has all been grown over now this is a photo back from the 60s apparently again just giving you a sense of us getting a chronology from those ashes next one next one oh good lord next one last thing and then we'll quit there's geophysical work that's been done on the west flank of Rainier west flank most of the folks working on this think that the west flank of the mountain is the most likely to go is the most likely to fail if there is a next mud flow coming in the next hundred years they expect this side to go and I have to show you the video clip going with this would you mind let's do it next one here it is many of the ridges low on Mount Rainier are formed of massive lava flows up to 2,000 feet thick but high on the mountain thinner steeply sloping layers are much less stable lava cliffs 50 to 100 feet high are separated by beds of rubble fragmented pieces of lava that are soft and easily eroded these rocks could break loose at any time nudged for example by a large regional earthquake or a steam eruption Mount Ranier is weakened even further by hydrothermal alteration a process that turns solid rock into soft and slippery clay atop the end of the Tahoma glacier in a landscape of altered rock the smell of sulfur taints the air boulders fall apart iron minerals crust the rock like rust slippery clay minerals coat the volcanic debris in the early 1900's this material fell suddenly onto the Tahoma glacier from Sunset amphitheater here this 600 foot cliff has been transformed from hard lava into a crumbling mass of weak rock by hot acid water moving through the volcano this chemical transformation requires water and heat which travels from the magmatic heart of the volcano water is present everywhere on Mount Ranier released by Sun and rain great so there's much work to be done we need to learn more about the history by studying more of these tests we need to do more geophysical work to get a sense if the west flank is really the next to go and these conferences I've gone through the last couple of summers has been with middle school teachers to try to educate the public mainly on the west side to understand the risk to practice evacuation drills literally for some of these communities and us here on the east side of the Cascade crest appear to be okay but as we learn more like with earthquake stuff as we learn more we become less and less confident that we're safe as we thought we were thanks so much for coming out tonight really appreciate it you

Channel: Central Washington University

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Keywords: Central Washington University Organization, Ellensburg Citytownvillage, Flood, Earthquake, geology, nick zentner, washington, History, washington state, Zentner Geology Lectures Downtown Ellensburg, rainier, Central Washington University, cwu geology, Geology Field Of Study, mt. rainier, mountains, Ice Age Floods, volcano, Central Washingtion University, Cwu Geological Sciences, Education, Cwu

Id: YcSPrk9l22I

Length: 65min 21sec (3921 seconds)

Published: Thu May 02 2013