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7 December 2022

The coastal section at Esterillos Oeste, Costa Rica

Callan documents a geological stroll along the coast of Esterillos Oeste, in central southern Costa Rica, investigating the sequence of sediment in the Punta Judas Formation (Mid-Miocene) exposed there. Fossils, sedimentary structure, diagenetic features, structural deformation, and modern weathering all make prominent appearances.


31 July 2020

Friday fold: Two Mile Run Overlook

I spied an anticline last weekend while engaging in a day of solo geologizing along Skyline Drive in Shenandoah National Park. At Two Mile Run Overlook, I gazed west toward the southern tip of Massanutten Mountain, and noted what appeared to be an anticline in the Blue Ridge foothills: Annotated: And here it is in Google Maps,  with the perspective rotated to looking ~along strike to the north, and I …


8 May 2020

Friday fold: Wills Mountain Anticline

Eric Fulmer (who pitched in with last week’s Friday fold) returns this week with another treasure. He writes, I was in Hopeville, WV a couple of years ago. The entire area between Cabins and Hopeville is a real joy (geologically and recreationally) as some of the most resistant rocks of the Mid-Atlantic Appalachians are folded and exposed in quick succession and with great relief. I am particularly fond of seeing …


1 May 2020

Friday fold: Hopeville Anticline

Reader Eric Fulmer has contributed a fold as a balm for the end of another week of COVID-19 self-quarantine. Check it out: Eric writes, I was in Hopeville, WV a couple of years ago. The entire area between Cabins and Hopeville is a real joy (geologically and recreationally) as some of the most resistant rocks of the Mid-Atlantic Appalachians are folded and exposed in quick succession and with great relief. …


11 July 2019

A submarine slump complex at Sandy Cove, Newfoundland

Traveling in Newfoundland, Callan visits a seaside outcrop showing a Proterozoic submarine slump complex, overprinted by tectonic cleavage and weathered by the sea.


10 September 2018

Monday Geology Picture: Geology Building at the University of Queensland

Earlier this year I visited The University of Queensland in Australia. For this week’s picture, I’m sharing an image of the lovely geology building at the university. The building is made out of gorgeous sandstone blocks… and there’s a dinosaur mural! And, lower down, check out the stones with the fossil carvings! What a great building. I think this is one of the most lovely and delightful geology buildings that …


15 July 2018

Chickie’s Rock, Pennsylvania

A virtual field trip to the deformed quartzites and metaconglomerates of Chickie’s Rock and Sam Lewis State Park in Lancaster County, Pennsylvania.


26 March 2018

Monday Geology Picture: Weathered Sandstone at Cottage Point, Australia

Here’s another picture from my recent trip to Australia. This picture shows a weathered  sandstone outcrop that I saw (by kayak!) at a place called Cottage Point. You can see fresh banded sandstone (light in color) underneath a darker weathering rim. Weathering has created some very interesting shapes in this outcrop! There are quite a few sandstone rocks in the Sydney area. They are frequently used as building stones — …


12 March 2018

Monday Geology Picture: Sandstone Building Stone

I’m currently on the east coast of Australia, where local sandstone is commonly used as a building stone. Above is a picture that I took this morning. This picture shows some beautiful building stones on display at the University of Newcastle. The cross-bedding and variable coloration of the sandstone layers is just gorgeous. What a lovely building stone!


23 January 2018

A kid and his slicks

On a family hike, Callan’s son finds some interesting smooth lines on a rock. What are they? What do they tell us? Tune in for a brief history of Appalachian geology.


18 October 2017

VGFC 2017: Limbs of arkose

The 2017 Virginia Geological Field Conference had a heavy arkose infusion. Meet some of these feldspar-rich Neoproterozoic sediments of the Lynchburg Group.


6 June 2017

Loading sags in homogeneous lithologies?

Can soft sediment deformation “loading structures” (ball & pillow) occur when the two strata are identical in composition? Grok on these field photos and chime in with your best hypothesis.


5 June 2017

3D models of sedimentary structures

I’ve been busy making 3D models lately. Here are three ones united by a theme of being sand that was deposited relative to mud. In one case we have scouring to make flutes, in another case we have have localized sagging to make “ball & pillow” structures, and in the third case we have an extraordinary submarine landslide deposit. For two of them, the shale has been preferentially etched away, …


8 May 2017

Monday Geology Picture: Sandstone Rock Art

First and foremost, I must apologize for the long gap in my blogging. I started the year with great intentions to revive this blog with my monthly science book posts… and then I didn’t post for several months! However, I think I have a good excuse: in January I found out that I am pregnant. Unfortunately, I have been suffering from an extreme form of morning sickness. I’ve been really, …


17 April 2017

Liesegang rings in a natural sandstone “tile”

An easter egg on a piece of toast? No, it’s a nice example of Liesegang rings in a slab of sandstone. Explore more in this blog post.


20 September 2016

A virtual field trip to examine the Peninsula Sandstone on Table Mountain

Take a virtual field trip to Table Mountain, near Cape Town, South Africa. Digital media to explore from the site include: a 3D model, 3 GigaPans, and a 360° spherical photo!


8 July 2016

Friday folds: Kinkell Braes, Scotland

When I took you on a virtual field trip to Kinkell Braes earlier this week, I didn’t mention that the sandstones are folded there, now did I? Let me remedy that omission now: That is a plunging anticline that you could actually take a plunge into: And here’s a syncline to match. Happy Friday. Hope your week was a good one, and that your weekend is even better.


4 July 2016

Virtual field trip to Kinkell Braes, Scotland

Walking along the shore east from St. Andrews, Scotland, along the seaside sandstones of Kinkell Braes, you encounter several extraordinary examples of geology. It’s a great place for the next stop on our Grand Tour of the geology of the British Isles. Here’s the scene: The first stop is a giant eurypterid trackway, potentially the largest invertebrate trackway in the world (Whyte, 2005), on the underside of an overhanging sandstone …


29 June 2016

Trace fossils in sandstone from Barns Ness

Check out this sandstone cobble I saw at Barns Ness – it comes bearing gorgeous trace fossils. Can you spot them? Lens cap for scale in all these photos. The next three are close ups of the burrows from the previous image: Plus two more, from other cobbles I encountered::


27 June 2016

Small faults in upper Old Red Sandstone, Dunbar, Scotland

Dunbar, Scotland, is a nice little seaside town that also happens to be the birthplace of the conservationist John Muir. My family and I have been based out of here this week on our European geological GigaPan expedition. But on our first morning, upon visiting Siccar Point (which is nearby), I threw out my back, and spent most of the next two days recuperating. I did manage a short walk …