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Episode 77 – Rock On, Colorado!

Dr. Graham Baird discusses the variety of old and new geologic formations along Colorado’s Front Range.

Dr. Graham Baird discusses the variety of old and new geologic formations along Colorado’s Front Range.

I'm Dr. Graham Baird. I'm a professor of geology, in the Department of Earth and Atmospheric Sciences.

You know, understanding the earth is vitally important for a whole bunch of reasons. One of which is if you think about your cell phone or your car or anything that society builds, you know, apart from wood. Any of the metals - where do we get those?

We get them out of the crust of the earth and they get concentrated in various locations because of geologic processes. And so that's one of the main reasons why do we need to understand the earth. And the other is, you know, just a more immediate things is you think about climate change. We've got to understand the earth. We've got to understand how the climate system is changing, how humans are causing that change. Because even geology has an influence on what are the CO2 concentrations in the atmosphere. And so humans are putting in more, but there's geologic processes taking some of it out and we got to understand all those balances too. And so geology is just one component of that - or a system that we need to understand. And so geologists also have to work with other earth scientists like meteorologists and you know, fluid dynamicists. And you could just put a whole list of other scientists that geologists need to interface with to understand the entire earth. It's where we live.

It reminds me of Carl Sagan's "it's all made of star stuff."


We're all just trying to understand that star stuff on one orb.


And what is your history behind geology?

Well, I grew up in upstate New York, right in the center of the state, which is a directly next to what's called the Adirondacks, which is a mountainous region in northern New York. And my family is very much into hiking, canoeing, fishing, cross country skiing. And so the Adirondacks were a logical place to do all those activities. And it turns out, the geology of the Adirondacks is fascinating. And I went to St Lawrence University, which is in Northwestern New York, and majored in geology there because I was interested in the natural world and you know understanding these rocks that I would run and ski through. And that led to an interest in basically educating others in the natural world. So I wanted to be a college professor, got a Phd at the University of Minnesota in geology of course, and got a job here in 2007 and been very happy teaching geology.

What made the Adirondacks stand out to you other than it being a mountainous region in your, around it? Can you maybe describe what the Adirondacks look like?

Well, it's a, it's fairly mountainous to the point where in terms of just size they're very similar to kind of the foothills, maybe not the high 12 to 14,000 peaks of the Front Range. But you know, the relief in terms of how deeper the valleys compared to the peaks, you know, the eight to 10,000 foot peaks in the foot hills, it's kind of that mountainous. But it's a big just kinda circular area. So it's not like a big belt, long line of mountains. It's just kind of this domal uplift. And there's many fascinating things about Adirondack geology, but what I got into is that the rocks there are fairly old - about a billion years old and they're also very kind of unique rocks. And so they're not typical rocks that you might see, you know, in other parts of the country. And that is always kind of a fascinating aspect. Like why are the rocks there so different and strange. And part of it is because of its age and part of it, it's related to other rocks in eastern Canada.

I guess that's a nice segue into the uniqueness of different areas of the United States. Let's let's talk about that belt of the Front Range. What are the differences in, in what, what kind of fascinating inquiries did you have coming to Colorado and the Rocky Mountains?

Yeah. So when you look at the geography of Colorado is very striking that you have fairly flat eastern plains and then you hit the Front Range and this just wall of mountains.

Like, Bam.

Yeah. And you know, the eastern plains are underlined by mostly flat-lying sedimentary rocks. And so they're pretty much in the position that the sediments that make up those rocks were originally deposited. And then you have a complicated area, right where the Front Range rises up, where you have faults and folding, which allowed the Front Range to be lifted up. And the sedimentary rocks that we see in the eastern plains used overlie the Front Range. But they've been eroded away when the Front Range was lifted up about 80 million years ago.

So going back to age, you mentioned a billion versus a million. Here we're saying that the rocky mountain is relatively new compared to the Adirondacks.

Yeah. This is a good question because there's a couple things you have to understand. One of which is yeah, about, you know, 50 to 80 million years was the time period when the Front Range was uplifted. So it is, with respect to the Adirondacks, that event was very new. Now we can go back to the Adirondacks. The up uplifted. The Adirondacks is actually a more recent event too. So there's actually some good comparisons there. But if you look at many of the rocks in the Front Range, they're significantly older. And so I talked about how the sedimentary rocks that underlying really, and the eastern part of Colorado used to overlie the Front Range but were eroded away because they were lifted up. What's now exposed in say Big Thompson Canyon, Poudre Canyon, Boulder Canyon, is the rocks that are underneath those sedimentary rocks. And those rocks range in age from the oldest is about a 1.8 billion. And the youngest is about a one point... It depends where you are, but mostly 1.4 billion. And there's some other events in there too. So I'm generalizing, but that encompasses most of the rocks that you're going to see if you drive up big Thompson Canyon or Poudre Canyon. Those rocks are about 1.4 to 1.8 billion years old.

I like how you traveled us into now the canyons of Rocky Mountain. There are totally different types of areas, especially on the Front Range. My, my first thought is I'm like Devils Backbone and or Red Rocks. What is the difference between what you find in the canyons? Say big Thompson and devil's backbone. They're so close, but yet they look completely different.

Yeah. Well we can start in the canyon. Those rocks in the canyon, like I said, 1.7 billion years old, kind of a good, just rough average for most of the rocks up there. And those were formed in the middle part of the crust. So probably about I want to say 15 to 25 kilometers down depending on where you are. And they were formed in a mountain building event where plates were colliding. And during that collision, the crust thickened, which causes higher pressure and temperature and causes metamorphism. So most of those rocks are metamorphic or igneous rocks produced by the melting of the mantle or the lower crust associated with that mountain building event.

My research focuses on looking at what happens, you know, in the mid to lower crustal regions when plates collide and mountains get built. And so I study the deformation  of the rocks because if you collide two plates, just like a car driving into a brick wall, the front of that car is going to get crumpled and thickened vertically. And that's exactly what happens to the crust. And so that's why the mountains are built. And that is in fact why the Rocky Mountains were uplifted too 80 million years ago. So there's been, Colorado experienced multiple convergent tectonic events that has thickened the crust and uplifted mountains. And of course competing against that -- and the answers 'why don't we see these 1.7 billion year old mountains anymore?' --Was acting at the surface is always weathering and erosion, which strips that material away. So there's been repeated mountain belts in the Colorado region. The only one that remains is the most recent, which is the Rocky Mountains because the other ones have eroded away.

So the first convergent plate tectonic event built the crust of Colorado and produced these rocks we see in Big Thompson Canyon. Moving out from the Canyon into the Devils Backbone area, you're in that little complicated area where I said there's lots of faulting and folding, which is the transition between these uplifted 1.7 billion year old rocks and these younger, what we would call Paleozoic rocks that are all about 250 million years or younger that make up the sedimentary rocks that we see, you know, in the eastern plains. And Devils Backbone is a really fascinating place because the rocks are folded there in that when you are in the parking lot of devil's backbone, you're pretty close to what we call the hinge zone of the fold.

And so if you look to the west, those rocks have been tilted down to the west and you look to the east, the rocks are tilted to the east. And so they form what we would call an anticline. And if you hike north from there, you can actually get into these 1.7 billion year old metamorphic rocks like you see in big Thompson Canyon because they're also further tilted down to the (verbal correction) *they’re also further tilted down to the south. And the way sedimentary rocks are deposited, one on top of each other, so the higher level ones are younger than the ones lower down. So because they're tilted to the south, down to the south. When you walk north*, you're walking into progressively older and older rocks and you eventually make it into the igneous and metamorphic rocks that are below sedimentary rocks. And you can get there. It's the Indian summer trail way north of there, you have to go along the blue sky trail and you can get up into there.

Do you have a personal preference of places to hike since you grew up outdoors-y around here, like just for your, aesthetics of geology. Where do you prefer?

Oh, I don't think I can't say there's one place. I have a number of places that I really prefer. Devils Backbone is certainly one of them, and it's close. There's some, you know, great geology, both looking at the sedimentary rocks, the anticline that's there. And if you can get far enough in North, you can get into the igneous and metamorphic rocks.

Bobcat Ridge at Masonville, I also really like.

There's the kind of the, you know, it's a big area with multiple trail heads, but the Lory state park and Horsetooth Mountain Park is great.

There's places south. North of boulder and Longmont is Rabbit Mountain, which I also like.

There's Coyote Ridge just south of Fort Collins.  There's a number of places up in Big Thompson Canyon, I think it's called Sheep Mountain, and also in Rocky Mountain National Park. I mean, I could go on and on and on. Right. These are all places I've repeatedly gone to because they're great.

Yeah. And when you, when it comes to your research, yeah. Okay. So you mentioned that you're studying these rocks here, up in these mountains, but you saying that it goes as far as 25 kilometers under the surface. So how do you actually study that? What, what does this, what does your research look like? Do you go out? You don't go out there with a pickax? What does that look like?

Well, so it ties into to what we were talking about earlier, quite nicely. So in tectonically stable areas, which aren't close to any plates colliding, like the central part of the U.S., the crust is around 30 to 40 kilometers thick. And when in tectonically active areas, like the west coast of North America, you have, and a good indication that's a tectonically after active area, the plates are colliding or sliding past each other depending on where you are along the west coast, you have volcanoes and earthquakes.

Like California.

Yeah, California is great. There's a big, what we call transform plate boundary, where the Pacific plate is sliding laterally against the North American plate and you get up into Oregon and Washington, it's a subduction zone. So one plate sliding beneath the other plate. And that sets up the volcanoes.

So if you want to study, say, Pacific northwest, the Andes or the Himalayas, which are all active plate boundaries where there's collision and you want to understand what's happening in the lower crust you're right, you can't, you don't have access to the mid and lower cross because it's, you know, 20, 30, 40 kilometers down or more.

So much dynamite needed.

Yeah. I mean, cause the crust, they're in, in those locations upwards, 70, 80 kilometers thick. So if you want to find out what's happening in the, you know, at 40 kilometers or lower, you can't do that on, you know, modern mountain belts that are being built. So you go to old mountain belts, which have had all that 20 kilometers of crust that's been sitting on top of that eroded away. And so in part of like, why do you want to study the Adirondacks? Why do you want to study these 1.7 billion year old rocks of the Colorado Front Range is that because they're so old, there's been a lot of erosion and those deep rocks are now exposed and so you can then look at those rocks, understand the processes that form those rocks and then use that as a model of saying, well these are the processes we see that were active, that built those mountain belts and formed those rocks, that then informs us of what's happening in the Himalayas at those depths now, or the Andes or the Pacific Northwest.

The complication to that is when you look at these really older rocks, you have to ask yourself, 'did plate tectonics operate in the exact same way at a billion years ago for the Adirondacks 1.7 billion year old years old for the Colorado Front Range? Or was there something fundamentally different?' Because you know, a billion years is a really long time and a lot has happened to the earth.

So you're having to come compare and maybe create some parallels, but knowing that there's going to be variance. So then that's, that's where the gap of knowledge and studying and, and guessing.

Yeah, absolutely. So, I mean that's another aspect of, there's some things we know are fundamentally different about plate tectonics. You know, at one point, 1 billion years ago for the Adirondacks, 1.7 for the Colorado Front Range. And so it's an, it's an added challenge of not only if we're going to try to understand modern plate tectonics using these old rocks as analogs, you also have to then say, well, we know this is an imperfect analog. And that also then informs us like, 'okay, how has plate tectonics changed over the span of Earth history?'.

I tried to involve both undergraduates and masters students into my research as much as possible. Just graduated Simone Müller with a master's degree and she did in the Big Thompson Canyon area. Adam Chumley, Undergrad from a few years ago, worked in the Big Thompson Canyon and so did Jake Hooker who was an Undergrad. And, I'm going to be looking for another Undergrad to work with in this coming year. And I think that's what's great about geology and the research I do is that it's accessible to the level that after a few geology classes and a little mentoring, you can define a question that needs answering and then go and do the field work and collect the rocks and do the analyses and draw conclusions about what's happening in the Colorado Front Range, looking at those older rocks.

Listeners can learn more from Dr. Baird TED-Ed lesson on crystals:  https://ed.ted.com/lessons/how-do-crystals-work-graham-baird

And  from  Dr. Baird’s companion webpage for my TED-Ed lesson:  https://www.unco.edu/nhs/earth-atmospheric-sciences/faculty-staff/crystals/


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