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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 …