AA 06 : A common type of lava flow composed of a jumble of lava blocks, with a rough, jagged, spiny, and generally clinkery or slaggy surface. Of Hawaiian origin, the term aa is applied to similar lava flows at other volcanoes (See: Clinkers)
Peter Bormann, Keiiti Aki, William H. K. Lee, and Johannes Schweitzer (Compilers and Amenders), Glossary of Terms Interest to Earthquake and Engineering Seismologists (Version 1), Publication records from external use of GFZ scientific infrastructure, Germany 2011. http://gfzpublic.gfz-potsdam.de/pubman/item/escido c:56137:3/component/escidoc:56143/Glossary_rev1.pd f, (ND/ Erthq - Amer) {980}