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16 April 2021

Friday fold: Colorado cluster

Friday means folds –
This week, we head to the Colorado Rockies for a butterfly-like presentation of a ptygmaticly folded granite dike within biotite schist.


21 November 2018

Brittle overprinting ductile in the South Mountains metamorphic core complex, Phoenix, Arizona

Today, we take a look at the structural geology that reveals the deformation evolution (first ductile, then brittle) of the South Mountains metamorphic core complex, south of Phoenix, Arizona. Expect lots of photos of smeared-out rocks, broken by faults.


26 October 2018

Friday folds: Mather Gorge Formation

It’s been a very Billy-Goaty week for me. Three times since Sunday afternoon, I’ve taken people to the Billy Goat Trail’s “A” loop in C&O Canal National Historical Park. On Tuesday and Thursday, it was my NOVA Physical Geology students. On Sunday, though, it was just my son and me. Good news! He helped me discover a new fold by exploring some new rock outcrops and climbing on them. He …


25 June 2018

Mafic volcanics atop felsic instrusives: Sonora Pass, California

Sonora Pass, California, is a lovely place to examine a volcanic-on-plutonic nonconformity that spans about 80 million years of missing time. Let’s check it out on a photo-rich virtual field trip!


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!


15 January 2018

Monday Geology Picture: Constantia Granite

For this week’s post, here’s a picture that I took yesterday during a Sunday afternoon hike with my family. We went for an easy stroll, baby and all, along the Alphen Trail in the Constantia region of Cape Town here in South Africa. My son is 3 months old now, and we’re just starting to go on some easy hikes as a family. The Alphen Trail is more of a …


6 November 2017

Monday Geology Picture: Inselberg View

For this week’s picture, here’s a lovely view of an inselberg and the Twelve Apostles section of Table Mountain here in Cape Town, South Africa. Note the layers of sedimentary rocks of which the mountain is made. In the foreground, you can see some rocks of the Cape Granite Suite, which is about 550 million years old.


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.


10 October 2016

Oddball Icelandic rocks, part II: granite!?!?

Silly Iceland! Don’t you know you’re not a continent?


16 September 2016

Friday fold: Centenary migmatite

The Friday fold is a guest submission from Bill Burton, who took the photo of these lovely ptygmatic folds in migmatite in a national park on the 100th anniversary of the founding of the Park Service.


11 July 2016

Kilometer to millimeter: 4 GigaPans to zoom in on Lewisian gneiss

I’m in the North-West Highlands of Scotland, enjoying spectacular geology and less-than-spectacular weather. I’ve been fairly productive on the GigaPan front, regardless, nipping outdoors when the weather permits to shoot outcrops and landscapes. One set I’m particularly pleased with is this suite of four images. They show the Archean-aged Lewisian gneiss, the oldest rock unit in the North-West Highlands, as exposed on a beachside outcrop east of Durness, Sutherland. The …


2 May 2016

Monday Geology Picture: Granite Boulder in the Forest

For this week’s “Monday Geology Picture” here’s a shot of a pretty granite boulder that I spotted during a forest hike in the Constantia region of the Cape Town, South Africa. No doubt, this boulder consists of ~550 million year old Cape Granite. There’s no scale in this picture, but the boulder is about 2 meters wide.


11 March 2016

Friday fold: disharmony in the Old Lyme Gneiss

Happy Friday – it’s the end of a very busy week for me, and I hope you too are looking forward to a fun and rejuvenating weekend. Here’s your Friday fold – like last week, a guest submission from Joe Kopera: Wowzers; that’s a looker! What are we looking at here? Joe writes: This photo shows geologic mapper and structural geologist Greg Walsh (USGS) explaining disharmonic folding to assembled geologists …


30 November 2015

Monday Geology Picture(s): Granite and Penguins at Boulders Beach, Simonstown

Last week I shared a few pictures from beautiful Boulders Beach just down the road in Simonstown, South Africa. This week I thought I’d share some more pictures of granite – and penguins! – at Boulders Beach. In the close-up shots, note gorgeous the potassium feldspar megacrysts in the granite. Most visitors to the beach focus on the penguins, but the granites are quite spectacular, too! Enjoy!


23 November 2015

Monday Geology Picture(s): Boulders Beach, Simonstown, South Africa

Just down the road from where I live there is a fantastic place to observe gigantic granite boulders: Boulders Beach in Simonstown. Actually, you can see granite boulders on many beaches in the greater Cape Town area. These granites are part of the regional Cape Granite Suite and are roughly 550 million years old. However, Boulders Beach is special because it has a particularly good collection of large boulders… and …


18 November 2015

Beach sand of coastal Maine

You could use a macro GigaPan of some pretty sand, I think. [gigapan id=”181069″] Link That’s sand from near Acadia National Park, in Maine. Exploring it, you can find both small chunks of Acadian granite, and green rods that are sea urchin spines. It’s fun – check it out.


25 June 2014

Pemaquid Point, Maine

Pemaquid Point, Maine, is a locally-owned and -managed park near an old lighthouse. I went there yesterday with my family. We’re on vacation in coastal Maine for a week. At Pemaquid Point, the action of waves have cleaned the rocks, and they offer a delightful three-dimensional look at Acadian-aged metamorphics and granite pegmatite dikes, with a fair amount of structural geology superimposed on the whole lot. Learn more about the …


17 June 2014

Weathering on Old Rag Mountain 2: Opferkessel

Yesterday, I pointed out an example of differential weathering on Old Rag Mountain, in Shenandoah National Park, in Virginia. Today, I’d like to shine the spotlight on another example of weathering to be seen along the trail there: little weathering pits that occur on the top of the granite outcrops. These are opferkessel. Some people call these “potholes,” a term I do not approve of in this context. To me, …


13 January 2014

Monday Geology Picture(s): Oudekraal Beach, South Africa

Yesterday was my 30th birthday. Amongst other wonderful things, my husband Jackie organized a surprise birthday party for me at Oudekraal, a beautiful beach (and national park) here in Cape Town. Bordered on one side by gigantic boulders and turquoise-blue waters and flanked on the other side by tall, jagged, gray-green mountains, Oudekraal is a stunning location. Jackie rented a kayak, brought plenty of delicious picnic food, and invited many …


24 October 2013

Exploring Wind River Canyon’s Great Unconformity in outcrop and hand sample (via GigaPan)

Over the summer, I shot these two GigaPans of the “Great Unconformity” in Wind River Canyon (Owl Creek Mountains), Wyoming: [gigapan id=”136109″] link [gigapan id=”136122″] link This week, Team M.A.G.I.C. (by which I mean my student Robin Rohrback-Schiavone) finished up a series of three macro GigaPans of rock samples from the site (made with our one-of-nine-in-the-world GIGAmacro rig by Four Chambers Studio): [gigapan id=”141715″] link [gigapan id=”143006″] link [gigapan id=”143007″] …