<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="1005" name="rocks and deposits" parent="287" scope="Solid masses that make up the earth's crust as well as accumulations of materials. Use for major rock types and unconsolidated deposits. For deposits of economic value, see related terms."/><uf><usefor name="crystals"/><usefor name="lithologic 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><usefor name="lithology"/><usefor name="rock composition"/></uf><bt><term thcode="2" code="287" name="earth characteristics" parent="1174" scope="The measurable, definable properties and features of the earth."/><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="414" name="fossils" parent="1005" scope="Recognizable remains such as bones, shells, leaves, burrows, impressions, or tracks of past life on the earth."/><term thcode="2" code="572" name="igneous rocks" parent="1005" scope="Rocks formed from melted rock that has cooled and solidified."/><term thcode="2" code="725" name="metamorphic rocks" parent="1005" scope="Sedimentary or igneous rocks which have undergone such intense changes in temperature, pressure, structural stress, or chemical environment that they are transformed into denser rocks."/><term thcode="2" code="2043" name="mineral deposits" parent="1005" scope="Deposits in which particular minerals are concentrated, typically noticed and studied if the minerals have economic value."/><term thcode="2" code="1370" name="permafrost" parent="1005" scope="Rocks and deposits in which the interstitial waters remain perennially frozen."/><term thcode="2" code="1804" name="petroleum" parent="1005" scope="Naturally occurring hydrocarbons, typically fluid or gas, often of economic use.  Includes oil, natural gas, and asphaltic compounds found in tar sands and oil shales."/><term thcode="2" code="1035" name="sedimentary rocks" parent="1005" scope="Rocks formed by the consolidation of loose, uncemented pieces of sediments."/><term thcode="2" code="1199" name="unconsolidated deposits" parent="1005" scope="Loosely bound sediments such as sand, gravel, and silt which tend to accumulate in low areas or valleys."/></nt><rt><term thcode="2" code="132" name="building stone resources" parent="798" scope="Deposits of rocks used in construction, including crushed stone and dimension stone. Dimension stone includes limestone and granite, quarried in large blocks, and shaped in cubes, panels and other forms."/><term thcode="2" code="667" name="lithosphere" parent="219" scope="The solid outer zone of the earth comprising the crust and the upper layer of the mantle."/><term thcode="2" code="730" name="meteorites" parent="900" scope="Masses of rock or metal from space that reach the earth's surface without burning up.  Use for 'meteors' or 'meteoroids' as well as 'meteorites'. USGS is more likely to have information about 'meteorites' since these are objects found on the earth."/><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="883" name="petrology" parent="464" scope="Branch of earth sciences concerned with the origin, structure, alteration, and composition of rocks."/></rt></descriptor>