15 April 2014
Last week I got to spend a couple of days in lovely Boulder, CO for a meeting (fortunately right before Sunday’s snow). The meeting (which was for the Thriving Earth Exchange’s Advisory Board – keep an eye out for updates!) kept us inside a lot, but the NCAR facility that hosted us has some fantastic views of Colorado’s Front Range and the famous Flatirons.
The boulders in the foreground and the flatirons in the back are all Fountain Formation, a 290-296 million year old arkosic sandstone. Obviously you can’t see from this vantage point, but there’s some beautiful interbedded layers of conglomerate and generally coarser sediment.
The sandstone is also quite red, which didn’t come out well in these photos, because it’s full of potassium feldspar and also has some iron oxide (hematite) in its cement.
Flatirons form when steeply inclined sedimentary layers are eroded into these triangular shapes like the base of an iron (here’s an old-fashioned one for reference). If it were a continuous (non-pointy) ridge, it might be called a hogback instead, referring to the ridge over a hog’s spine.
The NCAR lab is up on a mesa, and as I said on Twitter, I wouldn’t mind working at a place with a view like this!
The Pearl Street shopping area in downtown Boulder also has a nice array of sights for the geology lover – they have, in fact, decorated Boulder with actual boulders. One of my favorites was this migmatitic gneiss, which is split right down the middle so nerdy geologists can stick their faces right up to the prettiness. (It would have been even better if it had been polished just a tad more, but I can’t complain too much…)
According to this site, all of the rocks on the mall come from a quarry near Sedalia, CO. I’m not sure if the location is actually in the Sedalia quadrangle, which doesn’t mention it, but it could have come from Proterozoic or Paleoproterozoic basement rocks a bit further west.
Just down the block a little was an even more striking example, complete with explanatory plaque.
This was a really short trip, but I definitely need to get out for some serious hiking/climbing/exploring in the Boulder area. Preferably without snow, so I suppose I should wait a few more weeks!