{"thcode":2,"term":{"code":393,"name":"fission-track dating","parent":1680,"scope":"Laboratory technique for determining the age of rocks and other geological materials by counts of spontaneous and induced fission tracks left by the radioactive isotope uranium-238."},"uf":[{"name":"age dating (fission-track)","usewith":false},{"name":"fission-track method","usewith":false}],"bt":[{"code":1680,"name":"age estimation methods","parent":619,"scope":"Methods used to determine the age of earth materials, typically by laboratory analysis of properties of those materials."},{"code":619,"name":"laboratory methods","parent":734,"scope":"Techniques to analyze and test samples in a place equipped and designed for the work."},{"code":734,"name":"methods","parent":1,"scope":"Techniques, methods, procedures, or strategies for research, management, collection, or analysis of scientific information in USGS."},{"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":[{"code":438,"name":"geochronology","parent":464,"scope":"Study of the age of the earth by dating geological formations, rocks, and fossils."},{"code":954,"name":"radiometric dating","parent":609,"scope":"Methods for age determination of rocks and fossils by measuring the proportions of naturally occurring radioactive isotopes to their decay products."}]}