"Aa" is a type of volcanic lava that has a rough, jagged surface. It forms when lava cools and solidifies quickly, creating sharp edges and clumps. The name "aa" comes from the Hawaiian language, where it is used to describe this specific texture of lava. This type of lava is typically associated with shield volcanoes, which are broad and gently sloping. When mafic magma erupts, it can produce aa lava flows that move slowly and can be quite dangerous due to their rough terrain. Understanding aa is important for studying volcanic activity and its impact on the environment.