<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="451" name="geologic processes" parent="101" scope="All types of processes involving geological structures."/><uf><usefor name="lithification"/></uf><bt><term thcode="2" code="101" name="biological and physical processes" parent="1174" scope="All continuing activities, functions, and phenomena associated with organisms and non-living matter."/><term thcode="2" code="1174" name="topics" parent="1" scope="Themes, subjects, and concerns for which USGS information resources are relevant."/><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="1699" name="deformation (geologic)" parent="451" scope="Change in form and structure of geologic materials in response to stress, typically heat and pressure."/><term thcode="2" code="248" name="diagenesis" parent="451" scope="Chemical, physical, and biological changes in sediment during and after its conversion to rock (lithification)."/><term thcode="2" code="1683" name="earth tides" parent="451" scope="Periodic changes in the earth surface topography caused by the gravitational attraction of the moon and sun, measured with tiltmeters.  Used in studies of volcanic activity."/><term thcode="2" code="304" name="earthquakes" parent="451" scope="Ground shaking caused by the sudden release of accumulated strain by an abrupt shift of rock along a fracture in the earth or by volcanic or magmatic activity, or other sudden stress changes in the earth."/><term thcode="2" code="353" name="erosion" parent="451" scope="The process whereby materials of the earth's crust are loosened, dissolved, or worn away and simultaneously moved from one place to another."/><term thcode="2" code="2282" name="fluid migration" parent="451" scope="Movement or migration of fluids, including petroleum and other chemicals through earth materials by natural or anthropogenic forces."/><term thcode="2" code="482" name="glaciation" parent="451" scope="The geologic processes involved in the formation, movement, changes, and effects of large ice masses (glaciers)."/><term thcode="2" code="534" name="heat flow (earth)" parent="451" scope="Energy transferred by a difference in temperature through the surface of the earth."/><term thcode="2" code="562" name="hydrothermal processes" parent="451" scope="Natural phenomena relating to heated water generated by igneous activity."/><term thcode="2" code="608" name="isostasy" parent="451" scope="Condition of equilibrium or buoyancy of the earth's crust above the mantle."/><term thcode="2" code="1721" name="magnetic storms" parent="451" scope="A period of time during which the earth's magnetic field varies rapidly.  During magnetic storms, satellite electronics can be damaged through the build up and subsequent discharge of static electric charges and astronauts and high-altitude pilots can be subjected to increased levels of radiation."/><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."/><term thcode="2" code="1034" name="sediment transport" parent="451" scope="Transport of solid particles of unconsolidated rock and mineral fragments, chemical precipitates, or biological materials."/><term thcode="2" code="1036" name="sedimentation" parent="451" scope="Process of deposition of sediments (loose, uncemented pieces of rock, mineral fragments, or biological materials).  The sediments settle out of water or air into layers on a surface."/><term thcode="2" code="1736" name="slope processes" parent="451" scope="The down slope movement of earth material under the influence of gravity."/><term thcode="2" code="1710" name="soil formation" parent="451" scope="Geological, geochemical, and ecological processes that work together to produce soils."/><term thcode="2" code="624" name="subsidence" parent="451" scope="Settling, compaction, or caving in of land caused by subsurface mining, ground-water withdrawal, or pumping of oil and gas."/><term thcode="2" code="1145" name="tectonic processes" parent="451" scope="The structural forces affecting the deformation, uplift, and movement of the earth's crust."/><term thcode="2" code="1751" name="uplift" parent="451" scope="Local or regional rise in the elevation of the land surface, usually due to tectonic or volcanic processes."/><term thcode="2" code="1286" name="volcanic activity" parent="451" scope="Episodes during which gases, ash, and lava (molten rock) escape from vents in the earth's crust, accompanied by minor tremors."/></nt><rt><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="560" name="hydrology" parent="291" scope="Branch of earth science that deals with water as it occurs in the atmosphere, on the surface of the ground, and underground."/><term thcode="2" code="1195" name="tsunamis" parent="822" scope="Sea waves generated by submarine earthquakes, volcanic eruptions, or landslides, which are generally imperceptible in deep water but may be very destructive when striking the shoreline."/></rt></descriptor>