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.
amber - A fossilized resin from a coniferous tree that sometimes contains entrapped and preserved insects.
amphibole - group of generally dark-colored rock-forming inosilicate minerals, composed of double chain Si O), less mafic than basalt, but more mafic than dacite; rough volcanic equivalent of diorite.
atoll - A continuous or broken circle of coral reef and low coral islands surrounding a central lagoon.
autochthonous - Refers to something formed in its present location. backwash - The return flow of water down a beach after a wave has broken.
Thus water in the well rises above the surrounding water table.
asphalt - A dark bituminous substance found in natural beds. asthenosphere - The highly viscous, mechanically weak region of the upper mantle of the Earth that lies below the lithosphere at depths between 100 and 200 km below the surface.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.archean, archaean - An eon of geologic time extending from about 3800 to 2500 million years ago. The Archean eon is divided into four eras: Eoarchean, Paleoarchean, Mesoarchean, and Neoarchean.arkose - A variety of sandstone containing abundant feldspar and quartz, frequently in angular, poorly sorted grains.abyssal plain - The ocean floor offshore from the continental margin, usually very flat with a slight slope.