aa

A form of lava flow associated with Hawaiian-type volcanoes, consisting of basaltic rock, usually dark-colored with a jagged and loose, clinkery surface. Compare pahoehoe.

We...saw ‘pahoihoi’ or solid lava forming, and also ‘aa’ or clinkers.

Cooling and solidification frequently takes a different course [...] in lava flows, producing the clinker-like ‘aa’ lava.

Both pahoehoe and aa lava flows are common on the upper slopes of Mauna Loa with a preponderance of aa flows found at the lower elevations.

Variante von acetic acidInitialism of acetic acid.

Variante von acting ageInitialism of acting age.

Variante von alveolar-arterialInitialism of alveolar-arterial.

Variante von aminoacetoneInitialism of aminoacetone.

Variante von amino acidInitialism of amino acid.

Variante von approximate absoluteInitialism of approximate absolute.

Variante von arachidonic acidInitialism of arachidonic acid.

Variante von armature acceleratorInitialism of armature accelerator.

Variante von ascending aortaInitialism of ascending aorta.

Variante von atomic absorptionInitialism of atomic absorption.

Variante von author's alterationInitialism of author's alteration.

Variante von average audienceInitialism of average audience.

Variante von arctic-alpineInitialism of arctic-alpine.

Variante von always afloatInitialism of always afloat.

Variante von adjectivesAbbreviation of adjectives.

Variante von arteriesAbbreviation of arteries.

Variante von anaAbbreviation of ana (“of each, equal parts”).

I.