Pipe vesicles, outlined by thin black lines, represent fossilized concentrations of escaping gases - mostly H2O, CO2, and SO2 - migrating surface-ward in a cooling lava flow. In this case, gases migrated towards the surface where they encountered a viscosity(?) barrier and were redirected laterally between the lower flow and upper flow section.
Photographer: Mike Conway
Photo Date: June 2019
Photo Location Accuracy: Known Location