Leslie Gulch, Owhyee Mountains, Oregon

Geology 101: Leslie Gulch


In addition to driving on stupidly dangerous goat paths, WC spent the weekend in the deeply dissected volcanic rock of the Mahogany Mountain Caldera, in the southeastern corner of Oregon, near the Idaho state line.. Leslie Gulch is actually inside that 15.5 million year old caldera, which is some 15 kilometers wide and 20 kilometers…

Fisherman Road descends at an average 17% grade on a road chiseled into volcanic tuff and cobbles

WC Survived Fisherman Road


On a map, it looks like a nice way to get from Succor Creek Road over to the Owhyee Reservoir in southeastern Oregon. Even on Google Earth it looks pretty straightforward. It’s not. Don’t drive Fisherman Road. Maybe it was the August 2016 Cherry Road Wildfire, which burnt much of the area that Fisherman Road…

Arrowrock Spillway, looking south, Boise River

Some Notes on Arrowrock Dam


Arrowrock Dam is one of three major dams along the course of the Boise River. It’s the oldest of the three, completed in 1915. At 348 feet tall, Arrowrock was the highest dam in the world at the time. It’s primary purpose is irrigation; it holds the winter’s rain and snowmelt so that water is…

Lake Idaho and the Snake River Volcanic Province

Yet Another Giant, Ancient Lake


The Western Snake River Plain is a desert now. Sagebrush, bitterbrush and rabbitbrush growing on layers of ash and loess, which in turn lie on thousands of feet of basalt, congealed lava. It’s a desert, and a few minutes there in the summer will remove any doubts you might have that it is a desert.…

Almaden Mercury Mine spoil, April 2017

Notes on the Almaden Mercury Mine


Between 1932 and 1972, Nutmeg Mountain, eleven miles east of Weiser, Idaho, was a mercury mine. The mining was episodic, not continuous. Usually, it took a war to drive the price of mercury, which is used in explosives, to levels that made mining and extraction profitable. Changes in mining technology also affected the level of activity. Altogether,…

Engraving of Kilroy on the WWII Memorial in Washington DC

Geology 101: Meet the Ophiolites


Remember the “Kilroy was here” meme and doodle? It originated in World War II as a doodle by G.I.s. It was a way of saying, “An American G.I. was here.” Ophiolites are roughly analogous to Kilroy. Ophiolites are a characteristic geologic formation which says to a geologist, “An ocean was here.” And they turn up…