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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 …
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.
30 November 2022
Ichnoanalogue
Another glimpse of sand on the beach at Esterillos Oeste, Costa Rica… This time, I offer you a trace of an organism moving through the wet sediment: Note the two parallel lines of tracks laid down by little feet, and the central groove that overprints them. It reminded me very much of this similar arrangement, from near St. Andrews in Scotland, but: (1) this is the underside of a bed …
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
Raider of the Lost Anticlines
A solo hike in search of anticlines yields new outcrops and good views!
17 January 2018
Winter ichnology puzzle
Here’s a puzzler to warm up your chilly brain this Wednesday morning: Click to enlarge Figure out the story told by this set of imprints in the snow. The branch of science called ichnology studies the traces organisms leave behind. There’s a neat little story here. If you’ve got a guess, then you can check your answer by watching the video that this screenshot came from. It was posted on …
9 March 2017
Lugworm casts on the beach, Islay
Who dwells beneath the sands of Islay? Lugworms do. These embedded annelids process the sediment for food, extruding the undigested sand in charismatic piles that adorn the beach of Loch Gruinart.
8 December 2016
Silent samples, holey samples
Two very different samples tell stories that are full of holes. What’s going on with this weathered sandstone? What’s going on with this fossil scallop shell?
3 October 2016
A virtual field trip to Rathlin Island, Northern Ireland
Rathlin Island lies north of mainland Northern Ireland, a few miles offshore. I spent three lovely days there this past summer, investigating the geology and appreciating the wildlife (puffins and other sea birds, and seals). The geology is pretty straightforward: Paleogene basalt overlying Cretaceous “chalk” (really not so chalky here – technically, it’s the Ulster White Limestone). Here’s a suite of interactive imagery that you can use to explore Rathlin’s …
31 August 2016
Ball & pillow and other sedimentary structures in Graafwater Formation, Table Mountain
In Cape Town for the International Geological Congress, Callan hikes up Table Mountain and finds some superb primary sedimentary structures in sands and shales of the Graafwater Formation.
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.