I posted this photo elsewhere just recently, and got a little feedback as to what the irregular to polygonal cracks on the surface of these columnar-jointed basalt faces might be. Here are a few more photos. At this point, MOH and I had turned around on our Winnemucca-to-the-Sea Highway journey (turned from going toward Winnemucca to going away from Winnemucca), in order to spot a pullout to view the cracks better, and also to get a better look at the nearby Deep Creek Falls. (Okay, we really turned around to look at the falls.)
From the south side of Highway 140 right below the falls and a little less than 3 miles west of Adel, Oregon, here's the best roadcut I saw of the basalt: other roadcuts are in tight, narrow turns with no nearby pullouts.
A closer view.
The columns are weathering into somewhat rounded, rectangular to irregular shapes, which at times look like stacks of flattened pancakes and other times look like hoodooish sentinels watching over the road. Outcrops up the hill show the same patterns, exposures at the falls look merely columnar. So far, the consensus is that the basalt is undergoing incipient spheroidal weathering.
Additional ideas are welcome!
View Bend OR to Winnemucca NV in a larger map
Trip report to be continued...