Swirling lava from Rock Mesa, Oregon
The rhyodacite lavas from Rock Mesa are some of the strangest I've seen, with very glassy carapace (outer layer) than was almost greenish. There was also abundant swirling in the lavas of dense, glassy layers and bubble-rich layers. This betrays the viscous nature of these obsidian (or close) lava flows, where they can deform plastically, yet preserve this deformation as the flow continues to flow and solidify.
Image: Erik Klemetti
