You are browsing the archive for 2011 September.
30 September 2011
Straight-limbed open synform in an organic-rich formation of limited areal extent, featuring some brittle extensional features at the hinge. Kootenay National Park, British Columbia, summer 2011. (The bridge was broken before we got there.)
29 September 2011
By local prodigy Hannah Holland, elementary school student: Click through to make it bigger and see some details. Nice work, Hannah! Very impressive, and thanks for sharing!
28 September 2011
Northern Colorado’s route 287 connects Fort Collins, Colorado with Laramie, Wyoming. Along its length, it displays roadcuts into Archean-aged basement complex. Two of these outcrops are featured in this post: one metamorphic (mostly), and a second igneous (mostly), with some intriguing polka-dotted plutons.
27 September 2011
The geologic timescale: Where did those names come from? Here’s some etymological information I share with my Historical Geology students so that the names become meaningful symbols of ideas, rather than simply of bunch of nonsensical gibberish to memorize… Phanerozoic eon – Greek for “visible life” Cenozoic era – Greek for “new life” Quaternary – Latin for “fourth” Holocene – Greek for “entirely new” Pleistocene – Greek for “mostly new” …
24 September 2011
Along the Beartooth Highway, east of Cooke City, Montana, you will see this striking mountain: Click through to make it really big. That’s Pilot Peak. It’s a horn in Wyoming. My Rockies students get really jazzed when they see it. Glaciers carved away the rest of the mountain, leaving only this pyramidal spire. Awesome.
23 September 2011
Whilst at the JMU Field Camp in Ireland this summer, my former student Alan Pitts (author of Not Necessarily Geology), collected this lovely “pocket fold” near Derryclare Lough and brought it back to the States. A couple of weeks ago, after a graduate school advising session at a pub in Fairfax, Alan gifted me the sample. Though I was totally psyched for the brand new ancient pocket fold, it kind …
22 September 2011
More moki marbles: little concretions in sandstone, kind of like the ones I showed you Tuesday from Illinois. But these ones are from the Navajo Sandstone, a late Triassic or early Jurassic erg deposit from the Colorado Plateau. These photos were taken in Zion National Park, near Springdale, Utah (real close to the cross-beds I featured a month ago). They are tougher than the sandstone in which they formed, and …
21 September 2011
At the Burgess Shale this summer, it wasn’t all fun and fossils. I also saw a lovely, distinctly feather-shaped plume: This is an example of plumose structure – the subtle branching micro-topography that forms on the surface of a joint as the fracture propagates out from its origin. The more obvious “rib” that is perpendicular to the feathery plumes represents a moment, perhaps only a fraction of a second long, …
At the end of the summer, there was a conversation on Twitter about having a meet-up (“rendezvous” sounds more authentic, it was pointed out) for folks involved in geology social media: stuff like geoblogs and Twitter, but pretty much open to whoever’s into meeting up in some interesting place and exploring some geology together. Following up on the Twitter conversation, I’ve traded a few e-mails with one of the folks …
20 September 2011
Giant City State Park is a patch of protected forest south of Carbondale, Illinois, where there are some pretty cool exposures of Pennsylvanian-aged Makanda Sandstone. Here’s a typical look at one: Notice the deep chasm on the right. This leads, maze-like, to other flat-bottomed and vertically-walled canyons: The orthogonal joint sets produces some nice tall, cliff-like vertical exposures that reveal the history of these rocks in several stages: deposition by …