<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="1384" name="actinide series elements" parent="1426"/><bt><term thcode="2" code="1426" name="chemical element groups" parent="1382" scope="Groups shown at &lt;http://periodic.lanl.gov/&gt;"/><term thcode="2" code="1382" name="elements" parent="1174" scope="Chemical elements and element groups"/><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><rt><term thcode="2" code="1385" name="actinium" parent="1427" scope="Rare earth (actinide series) element with symbol Ac and atomic number 89 &lt;http://periodic.lanl.gov/89.shtml&gt;"/><term thcode="2" code="1392" name="americium" parent="1427" scope="Rare earth (actinide series) element with symbol Am and atomic number 95 &lt;http://periodic.lanl.gov/95.shtml&gt;"/><term thcode="2" code="1405" name="berkelium" parent="1427" scope="Rare earth (actinide series) element with symbol Bk and atomic number 97 &lt;http://periodic.lanl.gov/97.shtml&gt;"/><term thcode="2" code="1419" name="californium" parent="1427" scope="Rare earth (actinide series) element with symbol Cf and atomic number 98 &lt;http://periodic.lanl.gov/98.shtml&gt;"/><term thcode="2" code="1438" name="curium" parent="1427" scope="Rare earth (actinide series) element with symbol Cm and atomic number 96 &lt;http://periodic.lanl.gov/96.shtml&gt;"/><term thcode="2" code="1445" name="einsteinium" parent="1427" scope="Rare earth (actinide series) element with symbol Es and atomic number 99 &lt;http://periodic.lanl.gov/99.shtml&gt;"/><term thcode="2" code="1453" name="fermium" parent="1427" scope="Rare earth (actinide series) element with symbol Fm and atomic number 100 &lt;http://periodic.lanl.gov/100.shtml&gt;"/><term thcode="2" code="1491" name="lawrencium" parent="1427" scope="Rare earth (actinide series) element with symbol Lr and atomic number 103 &lt;http://periodic.lanl.gov/103.shtml&gt;"/><term thcode="2" code="1502" name="mendelevium" parent="1427" scope="Rare earth (actinide series) element with symbol Md and atomic number 101 &lt;http://periodic.lanl.gov/101.shtml&gt;"/><term thcode="2" code="1518" name="neptunium" parent="1427" scope="Rare earth (actinide series) element with symbol Np and atomic number 93 &lt;http://periodic.lanl.gov/93.shtml&gt;"/><term thcode="2" code="1524" name="nobelium" parent="1427" scope="Rare earth (actinide series) element with symbol No and atomic number 102 &lt;http://periodic.lanl.gov/102.shtml&gt;"/><term thcode="2" code="1539" name="plutonium" parent="1427" scope="Rare earth (actinide series) element with symbol Pu and atomic number 94 &lt;http://periodic.lanl.gov/94.shtml&gt;"/><term thcode="2" code="1547" name="protactinium" parent="1427" scope="Rare earth (actinide series) element with symbol Pa and atomic number 91 &lt;http://periodic.lanl.gov/91.shtml&gt;"/><term thcode="2" code="1593" name="thorium" parent="1427" scope="Rare earth (actinide series) element with symbol Th and atomic number 90 &lt;http://periodic.lanl.gov/90.shtml&gt;"/><term thcode="2" code="1605" name="uranium" parent="1427" scope="Rare earth (actinide series) element with symbol U and atomic number 92 &lt;http://periodic.lanl.gov/92.shtml&gt;"/></rt></descriptor>