Geotripper

So, with no sense of scale or other clues, anyone want to try and explain/describe this surface? For certain people I know, the answer may...

Three roads diverged in a green wood, And sorry I could not travel all three And be one traveler, long I stood And looked down one as far...

Back home from today's field study course in the western Sierra Nevada. The rock is marble of the late Paleozoic Calaveras Complex...wh...