#geological_time__geologic_time__geologictime  the time of the physical formation and development of the earth (especially prior to human history)
  supertype:  time  the continuum of experience in which events pass from the future through the present to the past
  subtype:  aeon__eon  the longest division of geological time; two or more eras
  subtype:  geological_period__period  a unit of geological time during which a system of rocks formed; "ganoid fishes swarmed during the earlier geological periods"
     subtype:  ice_age__iceage__glacial_period__glacialperiod__glacial_epoch  any period of time during which glaciers covered a large part of the earth's surface
     instance:  Quaternary_period__Quaternary__Age_of_Man  Tertiary_period__Tertiary  Cretaceous_period__Cretaceous  Jurassic_period__Jurassic  Triassic_period__Triassic  Permian_period__Permian  Carboniferous_period__Carboniferous  Pennsylvanian_period__Pennsylvanian__Upper_Carboniferous__Upper_Carboniferous_period  Missippian_period__Mississippian__Lower_Carboniferous__Lower_Carboniferous_period  Devonian_period__Devonian__Age_of_Fishes  Silurian_period__Silurian  Ordovician_period__Ordovician  Cambrian_period__Cambrian
  subtype:  geological_era__era  a major division of geological time; an era is usually divided into two or more periods
     instance:  Cenozoic_era__Cenozoic__Age_of_Mammals  Mesozoic_era__Mesozoic__Age_of_Reptiles  Paleozoic_era__Paleozoic  Precambrian_period__Precambrian  Proterozoic__Preoterozoic_era  Archean_era__Archean__Archeozoic__Archaeozoic__Archeozoic_era__Archaeozoic_era
  subtype:  epoch  a unit of geological time
     instance:  Holocene_epoch__Holocene__Recent_epoch  Pleistocene_epoch__Pleistocene__Glacial_epoch  Pliocene_epoch__Pliocene  Miocene_epoch__Miocene  Oligocene_epoch__Oligocene  Eocene_epoch__Eocene  Paleocene_epoch__Paleocene

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