<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="464" name="geology" parent="291" scope="Study of the planet earth, its composition, structure, physical and chemical processes, and history since its origin."/><uf><usefor name="subsurface maps"><usewith><term thcode="2" code="700" name="maps and atlases" parent="808" scope="Representation, usually on a flat surface, of a part or whole of the Earth or other parts of the universe.  Collections of maps linked digitally or bound together in a book are called atlases."/></usewith></usefor></uf><bt><term thcode="2" code="291" name="earth sciences" parent="1019" scope="Broad term for all science related to the study of the earth."/><term thcode="2" code="1019" name="sciences" parent="1" scope="Major educational fields, fields of study, and professional groupings within 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="312" name="economic geology" parent="464" scope="Scientific study of the formation, location, and use of marketable geologic materials including fuels, metals, minerals, and water."/><term thcode="2" code="438" name="geochronology" parent="464" scope="Study of the age of the earth by dating geological formations, rocks, and fossils."/><term thcode="2" code="468" name="geomorphology" parent="464" scope="Branch of geology dealing with surface land features and the processes that create and change them."/><term thcode="2" code="554" name="hydrogeology" parent="464" scope="Study of subsurface waters and geologic aspects of surface waters."/><term thcode="2" code="706" name="marine geology" parent="464" scope="Branch of geology concerned with the composition, geologic history, and earth processes of the ocean floor and the continental margin."/><term thcode="2" code="747" name="mineralogy" parent="464" scope="Branch of earth sciences concerned with the study of naturally occurring inorganic elements or compounds."/><term thcode="2" code="883" name="petrology" parent="464" scope="Branch of earth sciences concerned with the origin, structure, alteration, and composition of rocks."/><term thcode="2" code="1037" name="sedimentology" parent="464" scope="Branch of earth sciences concerned with the study of the origin, composition, transport, and changes of materials deposited by water, wind, or ice."/><term thcode="2" code="1104" name="stratigraphy" parent="464" scope="Branch of geology concerned with the study of the formation, composition, ordering in time, and arrangement in space of stratified rocks."/><term thcode="2" code="1117" name="structural geology" parent="464" scope="Branch of geology concerned with the distribution, position, shape, and internal structure of rocks."/><term thcode="2" code="1289" name="volcanology" parent="464" scope="The branch of geology that deals with volcanism and the processes involved in magma flow and eruption through a vent in the earth's surface."/></nt><rt><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."/><term thcode="2" code="288" name="earth history" parent="455" scope="The structural and compositional changes that the earth has undergone from its formation. Use for discussions of the whole earth (or large sections of it) instead of regional studies."/><term thcode="2" code="337" name="engineering geology" parent="339" scope="Branch of geology involved in the application of soil and rock mechanics, natural hazards, and other geological studies to the practice of engineering and construction."/><term thcode="2" code="455" name="geologic history" parent="287" scope="Record (and inferred reconstruction) of the origin and development of the earth since its formation."/><term thcode="2" code="1748" name="geologic maps" parent="700" scope="Maps depicting geological characteristics of the earth's surface, including lithology, geologic structure, age, and the results of crustal processes. Used where the product includes a depiction of the map as a whole, not for data sets that could be used to create a map."/><term thcode="2" code="451" name="geologic processes" parent="101" scope="All types of processes involving geological structures."/><term thcode="2" 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."/></rt></descriptor>