{"thcode":4,"term":{"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."},"uf":[],"bt":[{"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","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."},{"code":"3.4","name":"Felsic volcanic rock","parent":"3","scope":"A light-colored, fine-grained or aphanitic extrusive or hypabyssal rock, with or without phenocrysts and composed chiefly of quartz and feldspar."},{"code":"3.1","name":"Glassy volcanic rock","parent":"3","scope":"Extrusive rock having a texture which is similar to that of glass or quartz and developed as a result of rapid cooling of the lava without distinct crystallization."},{"code":"3.5","name":"Intermediate volcanic rock","parent":"3","scope":"A solidified body of volcanic rock having approximately equal light- and dark-colored minerals in its mode"},{"code":"3.3","name":"Lava flow","parent":"3","scope":"A solidified body of rock that is formed by the lateral, surficial outpouring of molten lava from a vent or a fissure."},{"code":"3.6","name":"Mafic volcanic rock","parent":"3","scope":"A solidified body of volcanic rock having abundant dark-colored minerals in its mode "},{"code":"3.2","name":"Pyroclastic rock","parent":"3","scope":"...clastic rock material formed by volcanic explosion or aerial expulsion from a volcanic vent."},{"code":"3.8","name":"Ultramafitite","parent":"3","scope":"A volcanic rock with color index (M) greater than or equal to 90"},{"code":"3.9","name":"Volcanic carbonatite","parent":"3","scope":"A rock of apparent volcanic origin composed of at least 50% carbonate minerals"}],"rt":[]}