Cation ratio dating
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.
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.
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.
astrobleme - A circular erosional feature that has been ascribed to the impact of a meteorite or comet.
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.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.Geology is the scientific study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them.The Greek derivation of the word "geology" refers only to the Earth, but since the beginning of the space age, the field has expanded to include the study of the solid matter of other celestial bodies, such as Mars and the Moon.