Ephemeral snow and ancient rock

By Phil Plait | February 10, 2011 7:00 am

I love living in Boulder. I have pretty much the same routine every morning: get The Little Astronomer off to school, start my coffee, grab a bowl of cereal (generic brand Cocoa Krispies, which I call Faux-co Krispies), walk across the house to my office, and open the window shade.

When I did this yesterday, here was my view:

Yeahup. I’m braggin’. Click to upliftenate.

Those are Boulder’s iconic Flatirons, named for their shape. Their geologic history is fascinating: They’re made of Precambrian rock — 600 million years or more old! — that was exposed to weathering when the first Rockies pushed up about 300 million years ago. That rock eroded and oxidized, forming red sediment. This was laid down flat and was covered by an inland sea 40 million years later. During the time of the dinosaurs this area became a floodplain, but at the end of the Cretaceous a second uplift began, forming today’s Rocky Mountains. This broke through the sediment, cracking it and lifting huge sheets of it nearly vertically: the Flatirons. North of here are similar but much smaller formations, and they aren’t raised as vertically. They really give a sense of the uplift and the incredibly slow march of time.

With the Sun shining so brightly, that snow in the picture hardly lasted until the afternoon. It was gone in the blink of an eye, the flap of a hummingbird wing, compared to the lifespan of those formations. The Earth is old, so terribly old… but events on a human timescale are still worth appreciating.

CATEGORIZED UNDER: Cool stuff, Pretty pictures
MORE ABOUT: Boulder, Flatirons, snow

Comments (47)

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  1. Science Ranch 2012 | Science Blogs and News | October 11, 2012
  1. Messier Tidy Upper

    Great view, lucky you! :-)

    .. events on a human timescale are still worth appreciating.

    Yes. As are those on a shorter than human timescale lasting mere nanoseconds or less too! 😉

    (The realm of the short-lived sub-atomic particles created by the super-colliders like the LHC frex.)

    The Earth is ancient beyond our fathoming true – yet it like our Sun is still middle-aged in relative terms.

    Plus comparing it to the oldest known exoplanet – the pulsar Jovian in the Messier 4 Glbular Cluster catalogued as PSR B1620-26 b & also known as the “Methuselah Planet” or “Genesis planet” – which is already a whopping 12.7 billion years old. (Source : Astronomy magazine exoplanets poster – Lynette Cook & Richard Talcott, circa 2005.)

    Now *that’s* an old world! We couldn’t survive there, the radiation even from an old pulsar would probably be deadly, there’s no surface to stand on, only (I’d expect) an endless unbreathable atmosphere blending at dark depths into supercritical fluid and hot ices before a core of metallic hydrogen wrapped mystery.

    Still, imagine what a view that must have! 😉

    That’s one of the things I love about astronomy, the perspective it brings!

  2. Messier Tidy Upper

    See :


    For more info on the exoplanetary Methuselah.

    Oh & if exoplanets could talk :


    The things the Methuselah exoplanet world must have seen. :-)

  3. Carol

    Well, such a nice photo…the snow in Boulder is still crunchy and hard. The Flatirons are spectacular.

  4. Ooooh… Purty!

    With the Sun shining so brightly, that snow in the picture hardly lasted until the afternoon.

    So your snow is already gone, while in New York, we still have 20-foot piles of plowed up snow in parking lots, and snow in our backyard that’s been there for weeks. Maybe you could have us over so we could warm up a bit?

    I was taking my kids to their martial arts class the other day, driving along the river, with a great view of the mountains (hey, they still count as “mountains”) on the other side, and thought it would make a great picture. (Sorry, I don’t keep a camera with me all the time.) What caught my eye most was the fact that it would have looked like a B&W photo (a la Ansel Adams), because with the cloudy sky and all the snow, the view was virtually devoid of any color aside from the red taillights of other cars.

  5. Actually, there is still snow on the southeast faces of the Flatirons this morning! I took this photo yesterday morning, and by 1 p.m. the rocks were brown. Perhaps I was mistaken and atmospheric haze fooled me. Either way, the snow won’t last long; it never does around here.

  6. Genny Mae Rowed

    That’s like my view! Except in different parts of the world.

  7. Howard Brazee

    I was talking about them yesterday when I delivered some food to my mother and mother-in-law at a high-rise retirement home across 28th from CU. The almost vertical red rocks were white. I speculated that they must have been wet when the snow hit, freezing the snow on them.

    It stays this cold so rarely that the sight was unusual.

  8. Grand Lunar

    “Perhaps I was mistaken and atmospheric haze fooled me.”

    To think some people have been fooled by places that LACK atmospheric haze!

    Anyway, beautiful picture, Phil!

    We need reminders of what a lovely planet we live on.

  9. At the risk of being ever so slightly pedantic, Phil, I have to correct you a little.

    The basement – and the mountains in Boulder – are indeed Precambrian crystalline rocks, both metamorphic and igneous, around 1.4-1.5 billion years old. But the Flatirons themselves are actually the Pennsylvanian-aged Fountain formation, which were thrust up by the uplift of that Precambrian basement during the Laramide Orogeny. (Because I will do ANYTHING to be able to use the word orogeny.)

    The Fountain formation is really cool. It’s the remnants of the alluvial fans that sat at the base of the Ancestral Rocky Mountains. It’s got a lot of very neat sedimentary structures in it that I could just go on and on about for ages. The formation’s an arkose – feldspar rich sandstone and conglomerate with a little bit of mudstone thrown in. You can actually find the Fountain all up and down the Front Range, though it only stands up like that in Boulder. The reason for that (or one of the main reasons, rather) is that in Boulder the Fountain is extensively cemented with more feldspar, which makes it a bit stronger and more resistive.

    The more you know! 😀

  10. Wow. Looks like my hometown here in Austria. Really wonderful view.

  11. Zucchi

    Beautiful. I miss living among real mountains.

  12. CP


    I just want you to know that I’m so glad I found your blog. It has become an essential part of my daily reading. The subject matter is great (I’m always irritated by bad science on T.V.) and, just as important, your delivery is perfect. Too often science is debunked in a boring way, by a boring person. Anyway, thanks..and remember to post a million times daily, as I need plenty of reading breaks between my classes.

  13. Aaron

    Flatiron…the elementary particle of, eh, flatness?

  14. which I call Faux-co Krispies

    This is why you’re a professional writer and I’m not.

  15. drow

    i lived in boulder for several years, and spent a lot of time hiking around NCAR hill. there’s something truly awesome about that city. i hope you’re enjoying it.

  16. Speaking of cool geology in Boulder, don’t forget about the super awesome disconformity that you can see up on Saddle Rock!

  17. Number 6

    Great entry…fascinating to hear the geological history of the Flatirons…In the Chicago land area, we have similar formations left by the blizzard that roared through here about a week ago. :)

  18. Buzz Parsec

    Rachael @9, doesn’t Marian Call have a line about not being able to say “orogeny” without laughing?

  19. Gary Ansorge

    ,,,and don’t forget the Grand Tetons. Those have the most sharply delineated peaks I’ve ever seen. They look almost like dragons teeth.

    Enjoy those mountains while you can. In another twenty years, they’ll be all rock, no snow,,,

    Gary 7

  20. Crudely Wrott

    Correct me if I’m mistaken Phil, but in the foreground tree to the left, aren’t those Magpie nests?

    When I was a just a little splinter in Wyoming there was a ten cent bounty on Pica pica and my father outfitted me with a single shot .22 rifle and bird shot ammo. For every pair of magpie feet I turned in at the local Soil and Conservation office I received a dime. That allowed me to buy lots of comic books and cherry phosphates down at the local drug store. In addition, I learned to shoot a long gun very accurately.

    These days the birds are protected by law back home. As an example of how time can change attitudes and assumptions I am perfectly happy that boys no longer venture out at dawn to shoot birds out of trees. Still, I’ll always value those crisp mornings, stalking through the dense riverside brush in search of my elusive prey. It was a real coming of age for me though I wasn’t even ten years old at the time. My, how things have changed.

  21. podrock

    Hey Phil, thanks for the great picture of our beloved flatirons. Too bad I can’t see them from my basement office, but they sure are nice to look at while I’m shovelling the walk.

    Also in that view, geologically speaking, is the Green Mountain Kimberlite, a Late Proterozoic-Early Paleozoic diatreme. It’s very small, and is easy to walk right over without noticing it. All the usual mantle mineral are there, except diamonds.

    Here’s a link with more info:


  22. Jeff

    Your best blog post yet, Phil. The best things in life are these brief moments where nature just takes the breath away and i’ve lived almost sixty years and that is my conclusion on what is good in life. I almost gag when I see all the technology ads because human creations are a joke compared to “god’s” creation.

    last two months almost every morning I wake up and venus is shining through my window into my eyes and here in the sunshine state it’s pretty much clear sky every morning. The realization of venus bowing to it’s giant SUN, golly, the earth bows to the same object.

  23. BTW, if you ever get bored of the views, I’ll be happy to trade houses with you, no charge.

  24. I lived in Laramie for a few years, and would occasionally drive down to Denver. Having grown up in non-mountainous Louisville, Kentucky, it was startling and fascinating to not just see mountains and rock formations, but to actually be able to see the structure of the geography in the rock formations in the area: to be able to actually look at enormous, shifted slabs of earth and see plainly the manner in which they had moved was a novel, wonderful thing. I miss your part of the country, but I also missed Kentucky while I was there…

  25. BJN

    You left out that the rock is a conglomerate sandstone or “arkose”. Any sedimentary formation is comprised of rocks older than the formation itself, but in a real sense all rocks are composed of older material since this tectonically active planet is a rock recycling machine.

  26. Dan

    The Fountain Formation is also responsible for a couple of other famous sites – Red Rocks and the Garden of the Gods. To put it in similar terms to Phil’s, without all those millions upon millions of years of geological activity, we would never have had U2’s Live Under a Blood Red Sky.

  27. Linda

    I’m actually doing a literature review paper for my Advanced Sedimentology class on the Pennsylvanian – Permian geologic history of the Denver Basin. Maybe I’ll pass it along when I’m done! :)

  28. Leon

    “Yeahup. I’m braggin’. Click to upliftenate.”

    That’s not very nice, Phil. Here I am stuck in California with the same drab, sunny skies and dry ground every day. I haven’t even been able to use my jacket much this winter. Curse you and your snowscapes! 😉

  29. alfaniner

    “With the Sun shining so brightly, that snow in the picture hardly lasted until the afternoon.”

    Just because the Sun is bright, doesn’t necessarily mean the snow will melt. :) All I have to do is look outside. Beautiful bright sunny day, -10 degrees. The snow will stay for a while. I’m only so aware because the bright day is my trade-off for the cold.

  30. Jeffersonian

    I’ve climbed 85 routes on several dozen of these bad boys. In doing so, you gain a large understanding of Fountain Formation because you’re standing on it, grabbing it all day, and walking past all the layers when you’re hiking down past the sides after rapping off. You learn about the pre-Cretaceous Sea that once covered this region (when the continent was in a different place), laying down eons of sediment and partnering alluvials. You learn that the different layers (which can be millions of years age difference) are not only different colors, but climb different underfoot. Some of the nearly 100 formations are closed certain times of year due to an increase in raptor nesting.

    Highly recommended climbing including the east face of 3rd Flatiron (the one with the giant letters) which has been called the best beginner’s climb in the universe (advanced climbers can run up it unroped without stopping – even without hands). The interlaced Feldspar has a lot to do with the aesthetic climbability. Personal faves are the ones behind NCAR.

    Phil, I recommend you learn the names of the 5 numbered and several more of the Flatiron features (they’re all named). Humans are nomenclature-based and this gives you a more intimate relationship with your skyline. The three in the center of this photo are #3, #2, and #1.

    @rachael. The Flatirons are not the only overturned-strata Fountain Formation: Red Rocks Amphitheater, Roxborough Park and the dramatic Garden of the Gods. None of which are as solid as Flatirons (which are more solid than Colorado granitics).

  31. Jeffersonian

    @19. just for pedantics; Though the glaciers in the Tetons have shrunk freaking dramatically (even compared to others in the central Rockies), the snow you see from the valley floor is is seasonal and disappears in a dry autumn. It peaks in late May/early June on the highest peaks of the range.

  32. Jeffersonian

    some people who don’t live near mountains may enjoy a bit of scale:
    The 3rd Flatiron is over 1000′ tall and the First is 850′ tall, so that gives you an idea how far away Phil needed to be to take the photo. The mountain in the rear is Green Mountain and rises nearly 3000′ above town to 8144′ (though because the Front Range has several peaks above 14,000′, Green Mtn barely registers as a foothill).

    (Yes, I loves me the Flats).

  33. Kath

    I grew up in Boulder, with the Flatirons shaping my skyline. I’m in New England now, but I miss that view! Thank you so much for sharing it so this Colorado expat could enjoy.

  34. Phil, I grew up with that view from a farm a few miles west of where you now sit. Your house sits (I think) on property that my relatives used to own. We had picnics out there and would gaze at the Flatirons on lazy summer afternoons. Lots of good family memories, college memories, and GRAD school memories tied up in that view.

    But, I would be remiss if I didn’t send you MY view of this snowy world, from 30 or so miles west of you and a few thousand feet higher up.

    Click on my name to see MY world.

    Other than that, yeah, I get up in the morning, get my coffee, check my email, and ponder at the view — seeing the backbone of the mountains a few miles west of me. This is a great state if you’re into geology, that’s for sure!



  35. podrock

    To be specific, the majority of the the “fins” or tall rocks in the Garden of the Gods are Lyons Formation, a nearly pure quartz sandstone (sand dunes and large scale cross-bedding) with an inner bed of arkosic conglomerate. The Fountain Formation forms the west side of GOGs, Balanced Rock being the best example of Fountain Formation in the park. Same with Roxbourgh Park, most of that is Lyons Sandstone. Type location is Lyons, Colorado, where the rock is quarried for landscaping flagstone.

  36. Chris Winter

    I was going to throw in, for Rachael, a link to “Orogeny” by Evoken. But after giving it a listen, I decided it was not that great.

    In any case, here’s to Boulder! Long may its mountains rise. My father was there at a summer institute for the Biological Science Curriculum study, back in 1966 or thereabouts. We drove out to meet him after. To see the Rockies rising ahead as we left Nebraska was a revelation. Ever since, Colorado has been my favorite state.

  37. Jesse

    I love gazing at the Flatirons and contemplating “deep time” and the immense geologic forces at work. Boulder is a unique place where many different ages of rock are dramatically exposed. Within a couple of miles, you can hike through a sequence of rocks back in time from the Quaternary to the Precambrian (with a big ~1.4 billion-year gap between the base of the Fountain Formation and the granitic basement rock making up the Front Range west of town).

    I highly recommend the book “The Geology of Boulder County” by Raymond Bridge. I just finished reading it, and it’s quite understandable to a non-geologist. It includes a bunch of hikes/field trips in the area.

  38. Brad

    They’ve aged well – they don’t look a day over 6,000. (C’mon – somebody had to say it!)

  39. Jeff J

    Like Mark T (comment 24) I grew up in Louisville Ky, not really experiencing mountains until I took a trip out to Boulder a few summers ago with some friends to hike and enjoy the mountain air! We went up to the royal arch and and poked around in the foothills quite a bit. We were lucky enough to be in Boulder for the Perseids, and even found a nice dark spot up in the hills one warm evening! I fell in love with the flat irons the moment I laid my eyes on them, and standing on top of them after the arduous hike up was a great experience!

  40. Messier Tidy Upper

    @34. ccpetersen Says:

    But, I would be remiss if I didn’t send you MY view of this snowy world, from 30 or so miles west of you and a few thousand feet higher up. Click on my name to see MY world.

    I tried that & didn’t get anything – just this :

    This content is currently unavailable.The page you requested cannot be displayed right now. It may be temporarily unavailable, the link you clicked on may have expired, or you may not have permission to view this page.

    message for your facebook page. :-(

    @30. Jeffersonian :

    Phil, I recommend you learn the names of the 5 numbered and several more of the Flatiron features (they’re all named). Humans are nomenclature-based and this gives you a more intimate relationship with your skyline. The three in the center of this photo are #3, #2, and #1.

    *Those* are their names!? Um, I would’ve expected something more imaginative & better than that! 😮

  41. sophia8

    I’m in Scotland, and just a few nights ago we had a TV show about the geology of Scotland. The country’s been shaped by billions of years of vulcanism and continental movements and there are amazing rock formations everywhere.
    Anyway, it inspired me to look into my local geology. It seems that the hill I can see from my window, in fact the hill this house is built on, is composed of ‘greywacke sandstone’ – sedimentary rock that’s close to half a billion years old. And this house that I’m sitting in is built from those same rocks……
    I’m a dancing, buzzing mayfly compared to them.

  42. ASFalcon13

    Beauty is in the eye of the beholder. Once upon a time I would have thought this was a pretty photo. Now that I’m a private pilot, all I see is a big CFIT hazard and structural icing. There’s only so much beauty you can derive from a photo when you realize that everything in it is trying to kill you. In other words, due to the effects of what you see in this photo, I get to cancel yet another flight. Thanks, Colorado!

    It’s all about point of view, I guess.

  43. Jeffersonian

    One is called “Spaceship”…

    type cross-section of flood plain and foothill here:

    Another extraordinary thing is that due to sparse ground-cover and river-cutting, many of the contact zones are easily visible underfoot. Millions of years touch each other in color.

  44. RAF

    I also enjoy a breakfast of “generic” cocoa krispies most every morning. Is that weird or what??

  45. Mitraria

    My husband likes the generic Cheerios. He calls them “Cheerioids”.


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