You are browsing the archive for 2017 November.
28 November 2017
I believe in tinkering with my teaching, and reflecting on the new approaches to see if I think they’re worth keeping or not. One of the topics I teach is the geologic history of Virginia. I do this because it’s essential knowledge to put the students’ upcoming field trip in context, but it’s also a nice example of how geologic techniques can be applied to understand the history of a …
27 November 2017
A trip to one of the most famous outcrops in the world, a place with a stratum that marked a profound shift in the state of the planet, and a profound shift in geologic thinking. Plus, for the author, it’s a romantic journey back in time.
Which of you can you tell me what this green book is all about (three volumes)? I’ll follow up in 1 hour with a post about the place where I took this photo.
24 November 2017
Here’s a guest Friday fold from reader Carl Brink: Carl tells me that this is: Precambrian Amphibolite schist float boulder from the Idaho Springs Formation in Rist Canyon west of Fort Collins, Colorado. Knife is 2.25 inches long. Thanks for sharing, Carl!
10 November 2017
The guest Friday fold comes to us from the Miocene of California, deposited in a releasing bend basin along the San Andreas Fault.
3 November 2017
This Friday, let’s return to Glacier National Park. Here are some folds in Helena Formation limestone: Can’t see them? Fair enough – the point of maximum inflection appears to be hidden behind a snow-filled gully: But in addition to that big fold, there are several kink bands in there, too. Let’s zoom in: Here they are: Zooming in further, on the right-most of these kink bands: …And here, with the …
2 November 2017
This morning on Twitter I was reminded of komatiites, those “extinct” ultramafic lavas that were relatively common eruptions during the Archean. I’ve actually got a good number of komatiite photos to share from my time last year in South Africa’s Barberton Greenstone Belt. But since time is short this morning, I’ll start with a short photo set of three images, all showing different aspects of how these ultramafic rocks weather …