anthracite - The most highly metamorphosed form of coal, containing 92 to 98 percent of fixed carbon. anticline - A fold of rock layers with a convex shape pointing upwards. aphanitic - An igneous rock in which the matrix grains are too small to be seen with the unaided eye. aquifer - A permeable formation that stores and transmits groundwater in sufficient quantity to supply wells.
archipelago - A group of islands; an expanse of water with scattered islands.
allochthonous - Refers to something formed elsewhere than its present location. alluvial fan - An alluvial fan is a triangular-shaped deposit of sediment at the point where a river emerges from a mountainous area and flows onto a more gently sloping plain.
alluvium - Sediment of sorted or unconsolidated sand, gravel, and clay that has been deposited by flowing water.
astrobleme - A circular erosional feature that has been ascribed to the impact of a meteorite or comet.
atmosphere (unit) - A unit of pressure equal to 101,325 newtons per square meter, or about 14.7 pounds per square inch.
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.
bank - The land alongside or sloping down to a river or lake.bar (stream) - An accumulation of sediment, usually sandy, which forms at the borders or in the channels of streams or offshore from a beach.barchan - A crescent-shaped sand dune moving across a clean surface with its convex face upwind and its concave slip face downwind.aeolian process - A geological modification, such as sand dunes or erosion, caused by wind activity. algal mat - A layered communal growth of algae observed in fossils and in present day tidal zones associated with carbonate sedimentation.alkali metal - A strongly basic metal like potassium or sodium.
Thus water in the well rises above the surrounding water table.