aa lava definition
1 A form of lava flow of basaltic rock, usually dark-colored with a smooth or ropey surface. It is one of two chief forms of lava flow emitted from volcanoes of the Hawaiian type, the other form being aa.  1859, R. C. Haskell, American journal of science and arts, series XXVIII: A'a' lava forms when the viscosity of the lava (e.g. because of high gas bubbles content and relatively low temperatures) and/or the strain rate of the flow (related mainly to eruption rate and steepness of the ground) are high. Noun[edit] 1  A form of lava flow of basaltic rock, usually dark-colored with a smooth or ropey surface. It is one of two chief forms of lava flow emitted from volcanoes of the Hawaiian type, the other form being aa.  We [...] saw ‘pahoihoi’ or solid lava forming, and also ‘aa’ or clinkers. Noun[edit] pahoehoe ‎(plural pahoehoes) 1  A form of lava flow of basaltic rock, usually dark-colored with a smooth or ropey surface. It is one of two chief forms of lava flow emitted from volcanoes of the Hawaiian type, the other form being aa.  1859, R. C. Haskell, American journal of science and arts, series XXVIII: Noun[edit] pahoehoe ‎(plural pahoehoes) A form of lava flow of basaltic rock, usually dark-colored with a smooth or ropey surface. It is one of two chief forms of lava flow emitted from volcanoes of the Hawaiian type, the other form being aa. A'a' lava flow burying a road on Etna (Oct. 2002). Brief explanation: A'a' lava is the most common appearance type of lava flows that cool down forming fragmented, rough, sometimes spiny, or blocky surfaces. On Earth, lava coils can be found on the Big Island of Hawaii, mainly on the surface of ropey pahoehoe lava flows. 'Snail-like' lava flows discovered on Mars for first time. Approximately 60m thick flow I is of compound pahoehoe type and highly weathered, exhibiting fragmentary tops at some places. Volcanoes are such an important part of the Hawaiian landscape and environment that the people who originally settled Hawaii, the Polynesians, worshiped a special volcano goddess, Pele. Not surprisingly, two words have entered English from Hawaiian that are used by scientists in naming different kinds of lava flows. One, pahoehoe, refers to lava with a smooth, shiny, or swirled surface and comes from the Hawaiian verb hoe, to paddle (since paddles make swirls in the water). The other, aa, refers to lava having a rough surface and comes from the Hawaiian word meaning to burn.. When these factors change, the same original lava can sometimes produce the other end-member known as pahoehoe lava, which has a smooth, often twisted surface. In addition, transitional types of lava between both a'a and pahoehoe lava can be found. Roy observes: the shapes of turtles found in the lava of the pahoehoe islets of Kamakahonu, later referred to by missionaries as 'The Plymouth Rock' of Hawai'i, are significant to history.
It is the most common appearance type of lava flows that cool down forming fragmented, rough, sometimes spiny, or blocky surfaces.