{"thcode":2,"term":{"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."},"uf":[{"name":"age dating (radiometric)","usewith":false},{"name":"argon-argon dating","usewith":false},{"name":"lead-210 dating","usewith":false},{"name":"radiometric age determination","usewith":false}],"bt":[{"code":609,"name":"isotopic analysis","parent":619,"scope":"Experimental determination of the proportion of a given isotope (or isotopes) in a sample."},{"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":[{"code":143,"name":"carbon-14 analysis","parent":954,"scope":"Method to determine the age of organic geologic and archaeological specimens, aged approximately 3,000 to 50,000 years, by determining the decay of the radioactive isotope carbon-14."},{"code":1374,"name":"potassium-argon analysis","parent":954,"scope":"Radiometric age determination by comparison of the concentrations of radioactive potassium and argon daughter products."},{"code":1007,"name":"rubidium-strontium analysis","parent":954,"scope":"Technique for dating ancient rocks based on measuring the ratio of the isotopes strontium-87 to ribidium-87 in samples. Uses the known half-life of radioactive isotopes of rubidium-87 that decay to isotopes of strontium-87 to determine rock ages."},{"code":1202,"name":"uranium-lead analysis","parent":954,"scope":"Radiometric dating technique to determine the age of earth materials from the ratio of the radioactive isotopes of uranium-235 or uranium-238 to the lead isotope decay products in the sample. The ratio is compared to the known half-life of the uranium isotopes."},{"code":1203,"name":"uranium-thorium analysis","parent":954,"scope":"Radiometric dating technique used to determine the age of earth materials based on determining the ratio of uranium-238 to the decay product thorium-230. The ratio is compared to the known half-life of the uranium isotope."}],"rt":[{"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":2278,"name":"environmental proxies","parent":734,"scope":"Biological, chemical, or physical features whose presence, characteristics, or behavior reflect environmental parameters of interest that cannot be readily or efficiently observed or measured directly."},{"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."},{"code":438,"name":"geochronology","parent":464,"scope":"Study of the age of the earth by dating geological formations, rocks, and fossils."}]}