So far, I've mainly emphasized that at the lower-pressure, cooler, near-surface of the flow, the obsidian seems to have deformed mostly brittley- that is, by breaking. I'm going to run a few photos over the next few days that clearly show it deforming either as a plastic or a liquid. Above is a very convoluted set of flow bands. The pumiceous phase is layered with relatively narrow and sparse vitreous bands. This is a situation where I kinda sorta think I see what's happening- a reversal of shear direction- but I'm not that confident, and I don't even know how to begin to explain. So I'll just say, "Ooo, look! Squiggle!"