Basaltic lava forming very rough jagged masses with a light frothy texture. Often contrasted with pahoehoe.
- Roads of black ash traverse it, winding through the otherwise untraversable aa.
- A serpentine flow meanders through formations of smooth pahoehoe lava and rough aa lava, the same forms common in basalt lavas.
- Very different from jagged aa, pahoehoe is the other general texture of newly solidified lava.
Mid 19th century: from Hawaiian’a-'a.