Posts Tagged ‘Maroon Bells’

The Creation of the Boulder Flatirons

January 18, 2017



Summer Flatirons with Sweet Pea Flowers Captured 29 June 2013 6:45am

We Boulderites love our Flatirons. In the dozen years that I’ve lived in Boulder, Colorado I have taken hundreds of photos of the Boulder Flatirons but I never knew what created these iconic structures. I dusted off my old (unread) copy of The Geology of Boulder County by Raymond Bridge and tried to figure out how the Flatirons were constructed.

Boulder has witnessed a complex geological history including the rise of two Rocky Mountain ranges, the present day Rockies and about 300 million years ago the Ancestral Rockies. Over the past 150 million years, Boulder’s environment ranged from inland seas to floodplains, deserts, swamps, seashores, then back to floodplain conditions again. Each setting deposited layers of sedimentary rock formed by broken fragments of older rock. Out of this rich geological past grew the set of outcroppings which defined the geomorphic term flatiron. There are flatirons all over the world. Other well developed flatirons in the Western US are found in the eastern Uinta Mountains in northwestern Colorado, the Waterpocket Fold in Capitol Reef National Park and the Superstition Mountains near Phoenix, Arizona.



Superstition Mountains Arizona Captured 10 December 2012 @ 5:07pm


The first stage of the construction of the Flatirons was the deposition of a thick layer of sand and gravel which occurred about 300 million years ago when the Ancestral Rockies were completely eroded. Powerful rivers draining these ancestral peaks carried sand and gravel to the adjacent plains, where they accumulated in a massive, 1,000 foot thick sediment that geologists have named the Fountain Formation. The Ancestral Rockies were eventually worn down completely and the eroded material formed younger sedimentary rock layers on top of the buried Fountain Formation. Even our Flatirons are made from recycled materials! 


Frosted Flatirons Captured 27 March 2009 @ Noon

The next stage of the Flatiron’s construction is the result of a unique event that occurred 70-80 million years ago known as the Laramide orogeny. This orogeny caused a renewed period of uplift and deformation from Canada to northern Mexico. The easternmost extent of this mountain building is represented by the Black Hills of South Dakota. This type of event is usually associated with the subduction of one continental tectonic plate under another. The subducted plate melts into a hot layer of viscous molten rock deep under the Earth’s crust known as the asthenosphere. In this instance the subduction zone is off the coast of California where it causes faults like the San Andreas as well as  earthquakes, volcanos, and the Sierra Nevada mountains. This event also uplifted the modern Rocky Mountains and the western great plains.

How could this event have affected Boulder which is 1000km (600 mi) east of the Pacific ocean? Geologists speculate that a particularly low-angled subduction of one tectonic plate beneath the other caused mountainous bulges deep into the North American continent. These forces pushed up the Flatirons and its neighboring mountains. The subducted plate, known as the Farallon Plate took an unusually shallow angle under the North American Plate. The Farallon Plate did not descend into the asthenosphere in the Earth’s mantle until it moved east causing the upheaval of the Colorado Plateau.


Reproduced From Light Train Productions

The sandwich of layers laid down by the erosion of the Ancestral Rockies and subsequent events were uplifted to their present position by this orogeny. Erosion re-exposed the Fountain Formation on the Flatirons.


The third event that made the Boulder Flatirons so unique is the cement that hardened them. Although the Fountain Formation stretches the length of the Front Range, Boulder is unique because of its dozens of well formed flatirons. This is due to a geologic quirk. Here, and only here, the Fountain’s layers are held together by an unusually strong cement called adularia, which is called moonstone when it’s gem-quality. This cement  formed only in Boulder because on two occasions—about 135 million and 94 million years ago warm, potassium enriched water welled up along an ancient fault zone that stretches between Eldorado Springs and Idaho Springs. The Fountain Formation’s grains reacted with that water to form the adularia that tightly cemented its grains together.


Spring Flatirons with Lilacs Captured 26 may 2016 @ 8:30 am

Another consequence of the uplifting of the Fountain formation is that it occurred on the Western Slope of Colorado as well. In the same way a drawbridge is tilted upward to allow ships to pass, the Rocky Mountains rose tilting up the overlying sedimentary rocks. In fact, the other flank of the  “drawbridge” can be seen in Aspen, Colorado on the Western Slope. The iconic Maroon Bells near Aspen form a portion of the Fountain Formation’s western counterpart called the Maroon Formation. Boulder and Aspen are linked by their geological icons.

Maroon Reflections

Maroon Reflections Captured 14 August 2013 @ 7:30am

For those who don’t believe all those geologists and their fancy pants scientific theories and speculations here is an alternative explanation for the construction of the Flatirons. This one was created by Jerry McElroy. He graciously gave me permission for the use of this photo and description of an alternative to the fact-based geological explanation…


Construction of the Flatirons (click to purchase a print)


The construction of the Flatirons in 1931 was the largest building project undertaken by the Civilian Conservation Corps. This massive development was designed to bring jobs to the Town of Boulder, Colorado and to help promote sagging post-depression tourism. Popular tours inside the Third Flatiron were discontinued in 1948 after a Ranger discovered that the interior space was taken over as a convenient den by black bear.


The last time I searched for photos of the Boulder Flatirons there were about 4,350,000 results! Here are some more of mine…


Cold Flatirons Captured 5 February 2014



Smoky Flatirons Captured 7 September 2010 @ 7:37am during Fire Season!



Flatirons from McClintock Trail Captured 13 October 2014 @ 10:50am




Spring Flatirons with Golden Banner Captured 7 May 2007 @ 10:45am




Dawn Flatirons Captured 11 January 2011 @ 7:30am





Mandy the Dog Loved the Flatirons Too. Captured 16 January 2013


I always thought the top of the 3rd Flatiron looks like Mandy the Dog…


The Mandy Flatiron Captured 2 February 2014 @ 1:25pm


This sculpture of the Boulder Flatirons was created by the late Cydd West a local artist who also used recycled materials to form his Flatirons…

Cydd West's Flatirons.jpg

Cydd West’s Flatirons Captured 13 August 2010 at 3:20pm


If you’re in Boulder here’s a nice 3 mi / 4.8 km round trip hike to a big flatiron that I call the Red Slab.



The Red Slab from the East




The Red Slab from the Sky (39°57’51.19N 105°17’7.80W)


To get there take the North Fork of the Shanahan Ridge Trail past the Mesa Trail and you’ll walk right up to this massive flatiron (see the push pin in the above satellite image).



The Red Slab from the Trail



Approach To Slab



The Bottom Of Slab is a Nice Spot to Have Lunch with a Flatiron…



…And Look Up An Ancient Streambed!





Maroon Reflections

August 22, 2013

Fortunately for photographers North America had two sets of Rocky Mountains. The first peaks, known as the Ancestral Rocky Mountains, rose to lofty heights before erosion began to wear them down. The sediments from these giant mountains created a huge mudflat in central Colorado. The Ancestral Rocky Mountains were completely eroded away by the time the modern Rocky Mountains formed. The present mountains lifted from the earth elevating a few of these maroon mudflats with them. Those remnants of the first Rockies, known as the Maroon Formation, can be viewed at the Maroon Bells (Maroon Peak and North Maroon Peak) in Aspen, Colorado as well as at the Flatirons above Boulder, Colorado.

Since I have already taken a gazillion panoramas of my hometown Boulder Flatirons I went to Aspen to get a dawn panorama of the “Deadly Bells” reflected in Maroon Lake. I tried this before but got rained on for 4 days. This time the weather cooperated and I joined a lineup of photographers at dawn…

Photographers Flock to the Maroon Bells

Photographers Flock to the Maroon Bells…The Most Photographed Mountains in Colorado

Here’s an upside down photo I captured from the reflection of Maroon Bells on Maroon Lake. Note the rocky sky…

The Maroon bells as Reflected In Maroon Lake

The Maroon Bells as Reflected In Maroon Lake

The dawns light forms a line which slowly descends the Bells…

The Bells at 5:45am

The Bells at 5:45am on 16 August 2013

The Bells at 6:10am

The Bells at 6:10am on 16 August 2013

Here’s someone’s timer-driven camera capturing a sunrise animation from a series of images…

Capturing an Animation of Sunrise on the Maroon Bells

Capturing a Video of Sunrise on the Maroon Bells

Later that morning I captured this view from an aspen grove above the Lake…

Maroon Bells From Aspen Grove 14 August 7:15AM @  39° 5'55.78

Maroon Bells From Aspen Grove 14 August 7:15AM @ 39° 5’55.78″N106°56’34.61″W

Maroon Lake forms the headwater of the Maroon Creek which flows down beautiful glaciated Maroon Canyon and on to hydrate the thirsty town of Aspen…

Maroon Creek Headwater

Maroon Creek Headwater

The flora of Maroon Canyon fill my memory…

Sunflowers Help Frame The Bells

Alpine Sunflowers (Tetraneuris grandiflora) Help Frame The Bells

The Fireweed is profuse…

Fireweed (Chamerion angustifolium)

Fireweed (Chamerion angustifolium)

Aspen Groves grow where the pines cannot…

Aspen Groves in the Maroon Canyon

Aspen Groves in the Maroon Canyon

Fossils show evidence of long times past…

Fossil Evidence of Early Vegetation

Fossil Evidence of Early Vegetation

Ptarmigan (Lagopus lagopus) call this place home…

Ptarmigan with summer plumage

Ptarmigan with Summer Plumage

This one views me with some suspicion…

Soon the snows will fall and these feathers will be replaced with white ones

Soon this Rocky-Colored Camouflage will be replaced with Snow White Plumage

A small herd of Rocky Mountain Mighty Moose (Alces alces) has recently moved into the Canyon. Here’s a mom getting some breakfast, my first photo of a female moose…

Moose Cow Getting Breakfast.

Moose Cow Getting Breakfast.

Snack break over, it’s time to get back to her calf…

It's Time to Find Baby

It’s Time to Find Baby and Get Some Privacy

This is the only yellow-bellied marmot (Marmota flaviventris) seen on this trip…

Yellow Bellied Super Marmots Did Not Reveal Their Presence

Yellow Bellied Super Marmots Did Not Reveal Their Presence

There were many sightings of Mountain Mandy in Maroon Canyon however…

Mandy (Canis lupus familiaris) takes a Break

Mountain Mandy (Canis lupus familiaris) Takes a Break

As does this grasshopper critter (I need some crowdsourcing help to identify this insect)…

Giant Grasshopper?

Giant Grasshopper?

It was a delightful week thanks to the Maroon Formation and I even captured my inner Summer panorama. I hope to go back in the Fall to collect some more colorful pixels.

Maroon Reflections

Maroon Reflections 14 August 2013 8:15AM MDT @ 39° 5’53.57″N, 106°56’32.52″W

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