{"thcode":2,"term":{"code":1340,"name":"volcanic rocks","parent":572,"scope":"A generally finely crystalline or glassy igneous rock resulting from volcanic action at or near the earth's surface, either ejected explosively or extruded as lava. The term includes near-surface intrusions that form a part of the volcanic structure."},"uf":[{"name":"lava","usewith":false},{"name":"pyroclastic","usewith":false},{"name":"tuff","usewith":false},{"name":"volcanic ash","usewith":false}],"bt":[{"code":572,"name":"igneous rocks","parent":1005,"scope":"Rocks formed from melted rock that has cooled and solidified."},{"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."},{"code":287,"name":"earth characteristics","parent":1174,"scope":"The measurable, definable properties and features of the earth."},{"code":1174,"name":"topics","parent":1,"scope":"Themes, subjects, and concerns for which USGS information resources are relevant."},{"code":1,"name":"Categories","parent":null,"scope":"Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."}],"nt":[],"rt":[]}