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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.
25 April 2018
Natural Bridge State Resort Park, Kentucky
A visit to a natural sandstone arch (or “bridge” as the locals call it) in eastern Kentucky yields unexpected bonuses, like fossil wood, Liesegang banding, and the honeycomb-like weathering pattern called “tafoni.”
13 February 2017
Q&A, episode 2
A new edition of “science and nature question and answer.” This week: why Massanutten Mountain isn’t longer, and why you’re never going to walk on the Sun.
16 December 2014
Back in 2011, when we were still living in D.C., Lily and I made a hiking trip out to Buzzard Rocks. It was a destination. Now that I live out here in the Fort Valley, I see Buzzard Rocks all the time, and I love it. It’s such a cool feature – a spot on the crest of the hill where you can see the slabby expression of steeply-dipping beds …
8 December 2014
Fluvial geomorphology of Mather Gorge
What hath the Potomac River wrought on the rocks of Mather Gorge? Some interesting shapes to the land surface reveal a fascinating history.
16 October 2012
Plane views: Leftovers
22 June 2012
Friday fold: an asymmetric anticline from Wyoming
Another landform seen out the window of that very productive photo-flight last March: That’s a breached plunging anticline – doubtless a Laramide structure. This was over Wyoming; I think here. Looking north-ish, along the axis of the fold: Note that the lengths of section line A and B are not equal: this anticline is asymmetric. The facing direction of the hogbacks on the left (west) indicate it’s not overturned, but …
23 May 2012
Fossil Falls fun
A few shots from Fossil Falls, in the southern Owens Valley, California… This is the now-dry river bed of the Owens River. There’s abundant evidence of water-induced erosion (potholes, polishing, etc.), but nary a drop of water to be seen – Though this particular portion of the Owens River drainage dried up in the Pleistocene, it parallels the more recent history of the valley’s water resources, which are now being …
13 April 2012
Friday folds: Turpan Depression
Rob Simmon of NASA’s Earth Observatory is the source for today’s Friday folds. Last week, he tweeted this image to me: That’s a excellent example of the outcrop pattern of a more or less horizontal outcrop of folded rock. To the north is a synform (notice that where streams have eroded it, the bull’s-eye pattern takes a notch inward toward the center of the structure), and to the south, a …
29 March 2012
New year’s atop Lion’s Head
My first view of Lion’s Head, the little butte northwest of Table Mountain, came through the fog on the morning that Evelyn and Jackie took Lily and I to Sea Point to see the migmatite: A lofty pinnacle – made of the same flat-lying quartz sandstone as the mesa of Table Mountain to the southeast: We went back to Lion’s Head on New Year’s Eve. After a delicious Thai dinner, …