Template:OkinaATemplate:Okinaā (also spelled aa, aTemplate:Okinaa, Template:OkinaaTemplate:Okinaa, and a-aa; Template:IPAc-en or Template:IPAc-en, from Hawaiian Template:IPA-haw meaning "stony rough lava", but also to "burn" or "blaze") is one of three basic types of flow lava. Template:OkinaATemplate:Okinaā is basaltic lava characterized by a rough or rubbly surface composed of broken lava blocks called clinker. The Hawaiian word was introduced as a technical term in geology by Clarence Dutton. [[Image:Aa large.jpg|thumb|left|Glowing Template:OkinaaTemplate:Okinaā flow front advancing over pāhoehoe on the coastal plain of Kīlauea in [[Hawaii|HawaiTemplate:Okinai]], United States.]]
The loose, broken, and sharp, spiny surface of an Template:OkinaaTemplate:Okinaā flow makes hiking difficult and slow. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface. At the leading edge of an Template:OkinaaTemplate:Okinaā flow, however, these cooled fragments tumble down the steep front and are buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an Template:OkinaaTemplate:Okinaā flow.
Accretionary lava balls as large as 3 metres (10 feet) are common on Template:OkinaaTemplate:Okinaā flows. Template:OkinaATemplate:Okinaā is usually of higher viscosity than pāhoehoe. Pāhoehoe can turn into Template:OkinaaTemplate:Okinaā if it becomes turbulent from meeting impediments or steep slopes.
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