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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 …
29 May 2020
Friday fold: Lopez Island tension gashes
The Friday fold shows some sheared quartz-filled tension gashes in sandstones of one of the San Juan Islands in Puget Sound.
25 October 2019
Friday fold: Identity of a BIF
The Friday fold is a slab of banded iron formation now dwelling in the University of Washington’s Department of Earth & Space Sciences. But where did it come from? India? Brazil? Perhaps you can help identify its provenance.
25 January 2019
Friday folds: more Marli Miller
Four Friday folds from Marli Miller’s online photo archive of geological images.
15 September 2016
Pillow basalts from eastern Washington: a 3D model
Since I showed off some Icelandic pillow basalts yesterday, today I thought I would showcase a new 3D model of big pillows in Columbia River basalt of eastern Washington, taken from a photo set I made when I was out there in May:
2 June 2016
Flood deposits of Glacial Lake Missoula outburst floods
Two weeks ago, I went on an awesome, informal field trip to eastern Washington State to visit the Channeled Scablands for the first time. My collegue Bill Richards of North Idaho College picked me up in Spokane and drove me halfway across Washington and back to Moscow, Idaho, over the course of a day. This is a region of the country where a glacier-dammed valley filled up with water (Glacial …
1 June 2016
Varves along Hawk Creek, Washington
Heading into the Columbia River Plateau, Callan and his colleague Bill Richards make a detour in search of some varves from Glacial Lake Columbia. They find them, a credit to the authors of “Washington Rocks!” – the new book from Mountain Press.
31 May 2016
A baked horizon in the Columbia River flood basalts
How did this bold orange layer develop? It’s seen in an outcrop near Wilson Creek, Washington, in the Columbia River basalts.
18 May 2016
Pillow basalt exposures in the Columbia River basalts
Pillow basalts form when mafic lava erupts underwater. Here are several examples from the Miocene Columbia River flood basalts, a large igneous province in eastern Washington state.
17 May 2016
Spheroidal weathering in Columbia River basalt
I’m in Idaho for the Rocky Mountain section meeting of the Geological Society of America. Yesterday, I was delighted to tour around in eastern Washington’s Channeled Scablands with my colleague Bill Richards (North Idaho College). I took a lot of photos, but here are two to start – lovely examples of “onion skin” style weathering in fractured basalt, producing “kernstones” of increasingly spherical shape: This is a particularly well expressed …
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.