{"thcode":2,"term":{"code":2022,"name":"alteration","parent":727,"scope":"Local changes in the mineralogy of a rock body due to low-grade metamorphism, weathering, or both.  May indicate underlying mineral deposits."},"uf":[],"bt":[{"code":727,"name":"metamorphism (geological)","parent":451,"scope":"Process by which rocks are altered in composition and texture by extreme heat, high pressure, or the action of chemicals."},{"code":451,"name":"geologic processes","parent":101,"scope":"All types of processes involving geological structures."},{"code":101,"name":"biological and physical processes","parent":1174,"scope":"All continuing activities, functions, and phenomena associated with organisms and non-living matter."},{"code":1174,"name":"topics","parent":1,"scope":"Themes, subjects, and concerns for which USGS information resources are relevant."},{"code":1,"name":"Categories","parent":null,"scope":"Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."}],"nt":[],"rt":[]}