{"thcode":4,"term":{"code":"3.7","name":"Alkalic volcanic rock","parent":"3","scope":"A volcanic rock that contains more sodium and\/or potassium than is required to form feldspar with the available silica."},"uf":[],"bt":[{"code":"3","name":"Volcanic rock","parent":"0","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 a lava.  The term includes near-surface intrusions that form a part of the volcanic structure."},{"code":"0","name":"Earth material","parent":null,"scope":"Geologic map unit classification (Bruce R. Johnson) version 6.2: A hierarchical classification of earth materials for digital geologic maps."}],"nt":[{"code":"3.7.1","name":"Phonolite","parent":"3.7","scope":"A volcanic rock defined in the QAPF diagram as having F\/(F+A+P) between 10 and 60%, and P\/(P+A) < 10%..."},{"code":"3.7.2","name":"Tephrite","parent":"3.7","scope":"A volcanic rock defined in the QAPF diagram as having F\/(F+A+P) between 10 and 60%, and P\/(P+A) > 90%..."}],"rt":[]}