Lava - aa-aa
Aa aa lava is a basaltic lava but at a lower temperaure than Pahoehoe at around 1000C. The lower temperature means that it is more viscous and flows as a blocky lava flow consisting of blocks called clinker. It moves slowly and creeps forward the top of the flow falling over the front face. The core of the flow is a paste like thick lava. Once cooled the surface is very rough and treachorous to walk on.