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9 December 2022

Pillbug tracks in ash from Mt. St. Helens

Reader Nancy Weidman (who supplied the Wind River boudinaged basaltic dike images from earlier in the week) sent me this interesting note: Your ichnoanalogue post reminds me of the insect or pillbug tracks I found in Mt. St. Helens ash deposited in Missoula, Montana. At least some of the tracks, if I recall correctly, ended in dead bugs, presumably dead after its breathing tubes clogged with ash. No fossils from …


30 July 2022

Well-preserved mudcracks in Belt argillite, Glacier National Park, Montana

Fresh from the field, Callan shares a quintet of beautifully preserved desiccation cracks in Mesoproterozoic Belt Supergroups sediments, exposed in Montana’s geological gem, Glacier National Park.


17 July 2020

Friday fold: Sandy Hollow from the air

The Friday fold is spied below, in the Montanan landscape near Dillon, from an airplane high above…


22 May 2020

Friday fold: Anticline in Glacier National Park

Some web research led to a serendipitous discovery and further exploration. Wherever you’re sheltering in place, you don’t have a view that’s this grand. Slip away for a few moments to the high country of Montana’s Glacier National Park, where an anticline may be seen in the towering cliffs…


10 May 2018

Last Stand, by Michael Punke

A reader of this blog recently recommended Michael Punke’s Last Stand. I thoroughly enjoyed his novel The Revenant, and so last week I started the audiobook version of the nonfictional Last Stand (2007). Last Stand is subtitled “George Bird Grinnell, the Battle to Save the Buffalo, and the Birth of the New West.” Prior to reading it, I knew little of Grinnell, save that he was a conservationist, and that he …


3 November 2017

Friday fold: More kinks from Glacier National Park

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 …


20 October 2017

Friday fold: Kink folds in Glacier National Park, part II

Over the summer, I treated you to a great big kink fold in the sedimentary rocks of Glacier National Park. Here’s another set: Did you see both of them in that first picture? – one bigger down below, one smaller up above. Both kink bands dip to the left. Let’s zoom in on the upper one: There’s more where this came from – stay tuned for more…. and in the …


9 August 2017

A suite of new 3D models

A showcase of five new 3D digital models of awesome rock samples and outcrops, produced using Agisoft Photoscan.


28 July 2017

Friday fold: Big kink fold in Grinnell Formation

It’s Friday! How about we celebrate with a beautiful kink fold from a gorgeous national park?


7 April 2016

New GIGAmacro images of rock samples

Another week, another batch of new images produced on my home-based Magnify2 imaging system from GIGAmacro. Leptaena brachiopod in (Mississippian?) limestone from Montana: [gigapan id=”185784″] Link Here’s the flip side of the same sample, with a lot of fenestrate bryozoans to see: [gigapan id=”185809″] Link Fault breccia from the Corona Heights Fault of San Francisco: [gigapan id=”185868″] Link Amygdular metabasalt from the western Sierra Nevada of California: [gigapan id=”185894″] Link …


31 March 2016

This week’s batch of 3D models

Anorthosite with lovely garnet reaction rims, a spherical hematite concretion, and some sweet breccia. Check them out and explore! [sketchfab id=”4453575da99743679a083363a0429b63″ start=”0″ spin=”” controls=”0″] [sketchfab id=”4333df612167415a8e216cef25e8cac6″ start=”0″ spin=”” controls=”0″] [sketchfab id=”cb58f446782d4736b699127884b46d16″ start=”0″ spin=”” controls=”0″]


29 March 2016

Four new GIGAmacro images

Here are a few new images I’ve been working on with my home-based Magnify2 imaging system from GIGAmacro. Archean basement complex gneiss from the Gallatin Range of Montana: [gigapan id=”185543″] Link (If this looks familiar, that’s because one of the samples I imaged with the Photoscan 3D modeling technique and published on Sketchfab the week before last.) Banded iron formation from Minnesota with ooids and stromatolites: [gigapan id=”185076″] Link Intrusion …


24 March 2016

Three new 3D rock sample models

Pahoehoe “ropes” on a basalt, sample site unknown: [sketchfab id=”d846c69192804bcfbcb2a625fd807af1″ start=”0″ spin=”” controls=”0″] Archean gneiss from the Gallatin Range of Montana: [sketchfab id=”4abba639632945aa8bd93c0d4e996e6a” start=”0″ spin=”” controls=”0″] Tafoni in Malmesbury Group turbidites, South Africa: [sketchfab id=”ddb2ec0a22214192907886d56e17ad11″ start=”0″ spin=”” controls=”0″]


25 September 2015

Friday fold: Macro GigaPan of Archean gneiss, Spanish Peaks, Montana

I don’t think I’ve featured this sample here before… It’s a lovely gneiss from near the trailhead for the Spanish Peaks, near Ted Turner’s Ranch in the Gallatin/Madison Range in southern Montana, not too far from Big Sky. Have fun checking it out in this macro GigaPan: [gigapan id=”161099″] link Happy Friday to all.


31 July 2015

Friday fold: a return to the duplex structure in the Gastropod Limestone

Some time ago, I featured as Friday fold the extraordinarily complex duplex structure to be seen in the Cretaceous “gastropod limestone” member of the Kootenai Formation at Sandy Hollow, Montana. Today, let’s take a deeper look through a couple of hand-shot GigaPan images: Here’s the bigger of the two: [gigapan id=”176119″] link Here’s one with students for scale: [gigapan id=”176475″] link


13 September 2013

Friday fold: Kink band in Lodgepole Limestone, Sacagawea Peak, Bridger Range, Montana

As I’ve mentioned previously, I spent some time making GigaPans this summer out west. Here’s Lily and me on the crest of the Bridger Range, enjoying the clear skies and great geology: When this portrait was taken (by our friend Lindsay), I was shooting this GigaPan: [gigapan id=”135511″] link Try exploring it to see if you can find today’s Friday fold: a kink band in the Lodgepole Limestone (a thinly …


3 January 2013

Inside the French Thrust

Callan zooms in on the meso-scale structure of the French Thrust fault, exposed in Sun River Canyon, Montana.


24 November 2012

Rock Cycle III: Igneous → Sedimentary

The Boulder Batholith outside of Butte, Montana, is actively weathering, and shedding off grus. In the third installment of the Transitions of the Rock Cycle series, we watch an igneous rock turn to sediment.


15 July 2012

One year

One year ago today, Lily and I had a fantastic wedding week in Montana. To celebrate the year we’ve been together since then, today I’ve got a gazillion photos to share – reliving the week for those who were there, and sharing it with those who weren’t able to make it… Our first group hike: Spanish Peaks: Cookout at Dave and Stacey’s place: Our second group hike: Sacagawea Peak: Norris …


2 January 2012

Monday Geology Picture: Bear Tracks in the Snow

Often, geology fieldwork can be a little bit dangerous. During some undergraduate field mapping in Montana, my classmates and I encountered some bear tracks in the snow. The above picture shows one of those bear tracks with a geological field notebook for scale. For the rest of the day, we kept a careful watch out for bears and tried not to stray too far from the field vans.