22 January 2011
I didn’t mention it yesterday, but there was one other structure that I saw at my newest outcrop on New 55. This is it:
That’s a bunch of fractures. The broken rock is being altered by preferential fluid flow through the fractures. The fluid is not inert; it’s chemically active, and reacting with the rock. These reactions produce the color and weathering differences that you note in the previous images. (Notice how the cores of each block are more spheroidal than the original angular outer shape of the block defined by the fractures.)
We saw something similar at Baker’s Beach in California last month:
And of course, we saw something similar last May in Shenandoah National Park, Virginia:
And then there is this example from the USGS Library in Reston, Virginia:
I just wanted to put all these photos together in one place (this post) and ask what I should call this phenomenon? I feel like it needs a good, evocative geologic name. The last example is dubbed “boxwork,” but I’m not sure that name really captures what’s going on in the top three locations.
Do we need to coin a neologism? Any nominations?