{"thcode":4,"term":{"code":"3.2","name":"Pyroclastic rock","parent":"3","scope":"...clastic rock material formed by volcanic explosion or aerial expulsion from a volcanic vent."},"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":"3.2.2","name":"Ignimbrite","parent":"3.2","scope":"The deposit of a pyroclastic flow."},{"code":"3.2.1","name":"Tuff","parent":"3.2","scope":"Consolidated or cemented volcanic ash."},{"code":"3.2.3","name":"Volcanic breccia","parent":"3.2","scope":"A pyroclastic rock that consists of angular volcanic fragments that are larger than 64 mm in diameter and that may or may not have a matrix."}],"rt":[]}