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Pennsylvanian period

(Encyclopedia)Pennsylvanian period: see Carboniferous period. ...

Triassic period

(Encyclopedia)Triassic period trīăsˈĭk [key], first period of the Mesozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table) from 205 to 250 million years ago. Throughout the Triassi...

Quaternary period

(Encyclopedia)Quaternary period kwətûrˈnərē [key], younger of the two geologic periods of the Cenozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table) from 2 millon years ago to t...

Paleolithic period

(Encyclopedia)Paleolithic period pāˌlēəlĭthˈĭk, –lēō–, pălˌ– [key] or Old Stone Age, the earliest period of human development and the longest phase of mankind's history. It is approximately coexten...

Permian period

(Encyclopedia)Permian period pûrˈmēən [key] [from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale, tablegeologic timescale, table) from 250 to 290 million years ago. Many ma...

Ordovician period

(Encyclopedia)Ordovician period ôrdəvĭshˈən [key] [from the Ordovices, ancient tribe of N Wales], second period of the Paleozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table) fr...

Neolithic period

(Encyclopedia)Neolithic period or New Stone Age. The term neolithic is used, especially in archaeology and anthropology, to designate a stage of cultural evolution or technological development characterized by the ...

synodic period

(Encyclopedia)synodic period sĭnŏdˈĭk [key], in astronomy, length of time during which a body in the solar system makes one orbit of the sun relative to the earth, i.e., returns to the same elongation. Because ...

Tertiary period

(Encyclopedia)Tertiary period tûrˈshēĕrˌē [key], name for the major portion of the Cenozoic era, the most recent of the geologic eras (see Geologic Timescale, tablegeologic timescale, table) from around 26 to...

Cambrian period

(Encyclopedia)Cambrian period [Lat. Cambria=Wales], first period of the Paleozoic geologic era (see Geologic Timescale, tablegeologic timescale, table) extending from approximately 570 to 505 million years ago. It ...