aa
ah-ah
Term for lava flows that have a rough rubbly surface composed of broken lava blocks called clinkers. Aa flows advance slowly, their hardened crust breaking and tumbling forward as molten lava pushes from behind. This produces a layer of lava fragments both at the bottom and top of an aa flow.
Etymology
Hawaiian. The word is said to come from the sound a person makes when walking barefoot across it. Whether or not the etymology is true, it is experientially accurate.
Notes
The counterpart is <a href="/word/pahoehoe/">pahoehoe.
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