Pyroduct lava splatter
Basaltic lava oxidizes according to the availability of water and oxygen during cooling. Here groundwater caused splattering of lava in a pyroduct (lava tube) in a cave on Hawaii. Pyroducts are conduits in which lava is conveyed for many kilometers on slopes sometimes less than 1° without substantial cooling. The lava flows thus produced give shield volcanoes their shape.
Stephan Kempe (distributed via imaggeo.egu.eu)