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20 July 2018

Friday fold: Alpine peak containing a high elevation recumbent fold

Via Twitter, a Friday fold from Maddy Rushing: #FridayFold, @callanbentley? pic.twitter.com/eaKIuuvFgB — Maddy Rushing (@komaddyite) May 25, 2018 This is in the Alps of Switzerland; I don’t know more about it than that. If you recognize the site or the geology, educate us in the comments!

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8 February 2018

A spectacular display of Earth science in the Alabama Hills

A detailed examination of an elegant photo of the eastern front of California’s Sierra Nevada, from the perspective of the Alabama Hills. How many different geologic phenomena can be packed into a single image? Let’s find out!

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1 February 2017

An oddball at Eshaness

In eastern Shetland, the sea chews away at the innards of a Devonian stratovolcano. But there’s an odd visitor there too – and we’re not talking about the blogger.

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1 June 2016

Varves along Hawk Creek, Washington

Heading into the Columbia River Plateau, Callan and his colleague Bill Richards make a detour in search of some varves from Glacial Lake Columbia. They find them, a credit to the authors of “Washington Rocks!” – the new book from Mountain Press.

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26 May 2016

Glaciotectonic thrust at Waubonsee Community College

Glaciers can cause thrust faults! Explore an example from a trench south of Chicago.

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8 December 2015

Considering the Spechty Kopf diamictite

I have known for a long time about a diamictite in the latest Devonian part of the Appalachian stratigraphic sequence, since it is exposed in the lowermost part of the section (western end of the outcrop) at Sideling Hill, Maryland. When I led field trips there, I talked students through the multiple possible origins for diamictites (sedimentary rocks that are poorly sorted, with significantly “outsized” clasts “floating” in a finer-grained …

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12 August 2015

Student guest post: the Belt Supergroup in Glacier National Park

As longtime readers know, late summer is when my Rockies students submit their final projects – web-based explanations of key geologic sites they examined during the trip. Today, I offer you a guest blog post by student John Leaming. You’ll notice that I’m not *completely* absent from the post, however – I make a couple of cameos as “sense of scale.” Enjoy, -CB ______________________________________________________________ Glacier National Park, Belt Supergroup I …

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18 July 2015

Purcell Sill → Dike, Grinnell Glacier Cirque, Montana

The Neoproterozoic Purcell Sill is a stark, obvious black stripe in the strata of Glacier National Park. Here it is emerging from behind “The Salamander” glacier, above Grinnell Glacier Cirque: Zooming in, you can see the “baked” (bleached) zones above and below this concordant intrusion. But this time, during my visit to this special place, I noticed a discordant offshoot from the main sill: See it? Up there at the …

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19 June 2015

Friday fold: subglacial drag fold (Pleistocene) in Cretaceous sediments, Alberta

Howard Allen, a retired petroleum geologist from Calgary, and longtime reader of this blog, contributed this week’s Friday fold: Subglacial drag fold (Pleistocene) in Upper Cretaceous Horseshoe Canyon Fm. bedrock (sandstone, shale). The locality is SE of Drumheller, AB at UTM 12U 394247 5692469 (WGS84). Did you hear that right? Yes, you did: This is Cretaceous aged sedimentary rock, folded by a Pleistocene glacier, tens of millions of years after …

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16 March 2015

Mechum River Formation, near Batesville, VA

A quick virtual field trip to the Neoproterozoic glaciogenic sedimentary rocks from the central Virginia Blue Ridge province: Can you feel the chill of Snowball Earth?

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