<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="281" name="drilling and coring" parent="379" scope="Cutting into the subsurface, for example into underground strata, ice, or a tree trunk, to remove material for examination. Intended for broad use wherever coring is done. The combination of this term with other terms will convey the context of the activity."/><uf><usefor name="core sampling"/><usefor name="coring"/><usefor name="ice core sampling"><usewith><term thcode="2" code="1072" name="snow and ice cover" parent="287" scope="Accumulation of snow or ice blanketing land surfaces."/></usewith></usefor></uf><bt><term thcode="2" code="379" name="field sampling" parent="376" scope="Collecting pieces or specimens or making measurements or observations at determined intervals or areas.  Results may be used as representative of the whole research area or population."/><term thcode="2" code="376" name="field methods" parent="734" scope="Research procedures and instrumental means to measure, collect data and samples, and observe in the natural areas where the materials, phenomena, structures, or species being studied occur."/><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="2063" name="augering" parent="281" scope="Use of a device with rotating blades and possibly helical flanges to dig holes in unconsolidated material for subsurface sampling."/><term thcode="2" code="2060" name="box coring" parent="281" scope="Use of a rectangular box pushed into soft sediment with a spade to facilitate lifting the sampled material, to isolate and extract relatively undisturbed underwater sediment."/><term thcode="2" code="2061" name="gravity coring" parent="281" scope="Use of a simple tube pushed into underwater sediments by an overhanging weight, to extract relatively undisturbed material for study."/><term thcode="2" code="2062" name="piston coring" parent="281" scope="Use of a piston mechanism and a weight with a triggering mechanism to drive a coring tube deep into underwater sediments for extraction and study."/><term thcode="2" code="2064" name="push coring" parent="281" scope="Use of a small, hand-held tube pressed into unconsolidated material for sampling."/><term thcode="2" code="2065" name="rotary drilling" parent="281" scope="Use of machinery to drive a rotating bit through earth materials in order to sample below the surface."/><term thcode="2" code="2066" name="vibracoring" parent="281" scope="Application of vibration to a coring device in order to achieve greater penetration for sampling unconsolidated material."/></nt><rt><term thcode="2" code="127" name="botany" parent="650" scope="The science of plants."/><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="464" name="geology" parent="291" scope="Study of the planet earth, its composition, structure, physical and chemical processes, and history since its origin."/><term thcode="2" code="484" name="glaciology" parent="291" scope="Science dealing with the features, origins, processes, and properties of snow, ice, glaciers, and ice sheets."/><term thcode="2" code="1325" name="well drilling" parent="775" scope="The process of artificial excavation for the purpose of withdrawing water, oil, or gas from underground."/></rt></descriptor>