WorldWide Drilling Resource

7 WorldWide Drilling Resource ® NOVEMBER 2018 Frequently-Used Geological Terms Part 75 Glossary Adapted from the Dictionary of Geological Terms R Radar - An electronic detection device for locating or tracking a distant object by measuring the elapsed time of travel of ultra- high-frequency radio waves emitted from a transmitter and reflected back by the object in such a way that range, bearing, height, and other characteristics of the object may be determined. Radar operation is unaf- fected by darkness, but moisture in the form of fog, snow, rain, or heavy clouds may cause attenuation (reduction of the amplitude of the signal) or reflection of the radio energy. Radial Fault - One of a group of faults which radiate from a central point. Radiation - The emission of atomic particles or rays from the nucleus of an atom. Also refers to the dispersal of a group of organisms into different environments, accompanied by diver- gent change in the evolutionary structure. Radioactive Clock - A radioactive isotope, such as carbon-14 or potassium-40, whose decay constant is known and is low enough to be calibrated to time units, usually years. Radioactive clocks are the basis of absolute age determinations and the specific element being used is sometimes designated as a clock, for example carbon clock. Radioactive Decay - The spontaneous disintegration of the atoms of certain nuclides (a kind of atom marked by the number of protons and neutrons and by the amount of energy contained in its nucleus) into new nuclides, which may be stable or undergo further decay until a stable nuclide is finally created. Radioactive decay involves the emission of alpha particles and beta particles, and is usually accompanied by emission of gamma rays. It always results in the generation of heat. Radioactive Element - An element capable of changing spon- taneously into another element by the emission of charged particles from the nuclei of its atoms. For some elements, such as uranium, all known isotopes are radioactive; others, such as potassium, only one of several isotopes is radioactive. Radioactive isotopes of most elements can be prepared artificially. There are only a few elements which are naturally radioactive. Look for more terms next month! Ground penetrating radar can be a use- ful tool in studying shallow subsurface geological environments on earth. G&O