Typical of arid and semiarid climates but not confined to them.abundant metal Iron, aluminum, magnesium, manganese, and titanium.Ores of the abundant metals only need to be 3 – 5 times as metal-rich as average rock.aa A Hawaiian term for a lava flow that has a rough, jagged surface. ablation As applied to glacier ice, the process by which ice below the snow line is wasted by evaporation and melting.
abyssal plain Large area of extremely flat ocean floor lying near a continent and generally over 4 km in depth.
acceleration The rate at which velocity changes, either by increasing or decreasing.
14C method A method for determining the age in years of organic matter by calculating the amount of radioactive carbon still remaining, as compared to the stable isotope, 12C.
Where possible, definitions conform generally, and in some cases specifically, to definitions given in Robert L Bates and Julia A Jackson (editors), Glossary of Geology, 3rd ed., American Geological Institute, Alexandria, Virginia, 1987.
Richardson (Englewood Cliffs, NJ, Prentice Hall, 1995).
40K/40Ar method A method used for the dating of potassium-bearing rocks by using the ratio of radioactive 40K to its daughter, 40Ar.