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7 December 2022
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
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
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
What hath the Potomac River wrought on the rocks of Mather Gorge? Some interesting shapes to the land surface reveal a fascinating history.
22 June 2012
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
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
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
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, …