Knowra A‘ā A‘ā A‘ā is a basaltic lava flow with a rough, jagged surface of broken clinker. Its moving interior can remain molten beneath a brittle, fragmenting crust.
Basalt : Basalt is a dark, fine-grained volcanic rock formed when low-silica lava cools. A‘ā flows are made chiefly of this low-silica volcanic rock.
Pāhoehoe : Pāhoehoe is basaltic lava with a smooth, billowy, or ropy surface. It is the most familiar contrast to A‘ā’s rough, broken clinker.
Volcanic hazard : A volcanic hazard is a process or material from a volcano that can harm people, infrastructure, or ecosystems. A‘ā advances as hot, destructive rubble and molten lava.
Hawaiian language : Hawaiian is a Polynesian language indigenous to the Hawaiian Islands. The geological term A‘ā comes from Hawaiian usage.
Lava flow : A lava flow is a body of molten rock that erupts onto Earth’s surface and moves under gravity and pressure. A‘ā is one surface-texture type of lava flow.
Block lava : Block lava is a lava-flow type whose surface consists of large, angular blocks with relatively smooth faces. Its blocky surface resembles A‘ā but typically has less loose, jagged clinker.
Hawaiian volcanoes : Hawaiian volcanoes are volcanic systems of the Hawaiian Islands, dominated by basaltic eruptions and shield-building activity. Their basaltic eruptions commonly produce A‘ā and pāhoehoe flows.
Hawaiian Volcano Observatory : The Hawaiian Volcano Observatory is a United States Geological Survey observatory monitoring Hawaiian volcanoes. Its field documentation records A‘ā flows and their behavior.
Lava viscosity : Lava viscosity is its resistance to flow, shaped by temperature, composition, crystals, and gas bubbles. Cooling and crystallization raise viscosity as an A‘ā flow advances.
Transition from pāhoehoe to ʻaʻā : A transition from pāhoehoe to ʻaʻā is a change in lava surface form as a flow cools, thickens, or deforms. One flow may change from smooth pāhoehoe to rough A‘ā as conditions shift.
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