<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="619" name="laboratory methods" parent="734" scope="Techniques to analyze and test samples in a place equipped and designed for the work."/><bt><term thcode="2" code="734" name="methods" parent="1" scope="Techniques, methods, procedures, or strategies for research, management, collection, or analysis of scientific information in USGS."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="955" name="Raman spectroscopy" parent="619" scope="Non-destructive chemical analysis technique in which a sample of material is irradiated with visible or near-infrared light from a laser, and the wavelength-dependent observations are used to understand chemical structure, phase and polymorphy, crystallinity and molecular interactions of the material."/><term thcode="2" 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."/><term thcode="2" code="1670" name="camera calibration" parent="619" scope="Optical calibration of cameras that are typically used in airborne remote sensing."/><term thcode="2" code="153" name="chemical analysis" parent="619" scope="Chemical techniques used to identify the composition of substances."/><term thcode="2" code="212" name="core analysis" parent="619" scope="Study of the composition and layers of cylindrical samples of rocks, trees, ice, and other materials extracted by drilling into a mass. Intended for broad use for the analysis of all types of core samples. The combination of this term with other terms will convey the context of the activity."/><term thcode="2" code="224" name="culturing (specimens)" parent="619" scope="Growing microorganisms, tissue cells, or other living matter in a specially prepared nutrient medium for diagnostic or scientific use."/><term thcode="2" code="370" name="faunal and floral census (microscopic)" parent="619" scope="Records of counts of the different microscopic species in a core, soil, sediment, rock or water sample to determine geologic age or other characteristic of the sample.  Use for microscopic examinations."/><term thcode="2" code="493" name="grain-size analysis" parent="619" scope="Method of studying soils, sediments, sands, or rock by determining the size, distribution, and proportion of selected particles."/><term thcode="2" code="609" name="isotopic analysis" parent="619" scope="Experimental determination of the proportion of a given isotope (or isotopes) in a sample."/><term thcode="2" code="2088" name="laboratory experiments" parent="619" scope="Procedures carried out in a laboratory under controlled conditions to test specific scientific hypotheses."/><term thcode="2" code="721" name="meristics" parent="619" scope="Branch of zoology concerned with classifying animals by counting and measuring body parts."/><term thcode="2" code="740" name="microscopy" parent="619" scope="Laboratory methods using instruments that employ optical lenses or radiation to study objects too small to be seen by the naked eye."/><term thcode="2" code="860" name="paleomagnetic analysis" parent="619" scope="Determination of the intensity and direction of residual magnetism in rocks to study changes in the earth's magnetic field during past geologic time."/><term thcode="2" code="880" name="petrography" parent="619" scope="Use of optical microscopy for the description and classification of rocks."/><term thcode="2" code="907" name="plant and animal testing" parent="619" scope="Use of live or dead organisms for scientific study."/><term thcode="2" code="2082" name="subsampling" parent="619" scope="Preparation of study materials by dividing or slicing cores, samples, or other collected materials."/><term thcode="2" code="1160" name="therapeutic methods" parent="619" scope="Methods of  restoring health with remedial agents or treatments."/><term thcode="2" code="1188" name="tree ring analysis" parent="619" scope="Study of the variations in width and number of tree rings to date historical events and to study periods of climatic and hydrologic changes."/></nt></descriptor>