banded iron formation - Rock consisting of alternating light and dark layers of iron-rich chert (hematite and limonite) formed approximately 3,800 million years ago.
bank - The land alongside or sloping down to a river or lake.
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.
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.
angle of repose - The steepest slope angle in which particular sediment will lie without cascading down.