barrier island - A long, narrow island parallel to the shore, composed of sand and built by wave action.
basalt - A fine-grained, dark, mafic igneous rock (~50% Si O) composed largely of plagioclase feldspar and pyroxene; rough volcanic equivalent of gabbro.
barchan - A crescent-shaped sand dune moving across a clean surface with its convex face upwind and its concave slip face downwind.
bankfull stage - The height of water in a stream that just corresponds to the level of the surrounding floodplain.
bar - A unit of pressure equal to 10 to the sixth dynes/square centimeter; approximately one atmosphere.
Geological analysis relies mainly on chemistry, physics and mathematics. a'a' lava - basaltic lava characterized by a rough or rubbly surface composed of broken lava blocks called clinker.
A-horizon - The uppermost layer of a soil, containing organic material and leached minerals.