geologic time

Definitions of geologic time
  1. noun
    the time of the physical formation and development of the earth (especially prior to human history)
    synonyms: geological time
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    Phanerozoic aeon
    the period from about 5,400 million years ago until the present
    Age of Mammals
    approximately the last 63 million years
    Quaternary period
    last 2 million years
    Holocene epoch
    approximately the last 10,000 years
    Pleistocene epoch
    from two million to 11 thousand years ago; extensive glaciation of the northern hemisphere; the time of human evolution
    Tertiary period
    from 63 million to 2 million years ago
    Pliocene epoch
    from 13 million to 2 million years ago; growth of mountains; cooling of climate; more and larger mammals
    Miocene epoch
    from 25 million to 13 million years ago; appearance of grazing mammals
    Oligocene epoch
    from 40 million to 25 million years ago; appearance of sabertoothed cats
    Eocene epoch
    from 58 million to 40 million years ago; presence of modern mammals
    Paleocene epoch
    from 63 million to 58 million years ago; appearance of birds and earliest mammals
    Age of Reptiles
    from 230 million to 63 million years ago
    Cretaceous period
    from 135 million to 63 million years ago; end of the age of reptiles; appearance of modern insects and flowering plants
    Jurassic period
    from 190 million to 135 million years ago; dinosaurs; conifers
    Triassic period
    from 230 million to 190 million years ago; dinosaurs, marine reptiles; volcanic activity
    Paleozoic era
    from 544 million to about 230 million years ago
    Permian period
    from 280 million to 230 million years ago; reptiles
    Carboniferous period
    from 345 million to 280 million years ago
    Upper Carboniferous period
    from 310 million to 280 million years ago; warm climate; swampy land
    Lower Carboniferous period
    from 345 million to 310 million years ago; increase of land areas; primitive ammonites; winged insects
    Devonian period
    from 405 million to 345 million years ago; preponderance of fishes and appearance of amphibians and ammonites
    Silurian period
    from 425 million to 405 million years ago; first air-breathing animals
    Ordovician period
    from 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds
    Cambrian period
    from 544 million to about 500 million years ago; marine invertebrates
    Precambrian period
    the eon following the Hadean time and preceding the Phanerozoic eon; from about 3,800 million years ago until 544 million years ago
    Proterozoic aeon
    from 2,500 to 544 million years ago; bacteria and fungi; primitive multicellular organisms
    Archaeozoic aeon
    the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life
    Priscoan aeon
    the earliest eon in the history of the Earth from the first accretion of planetary material (around 4,600 million years ago) until the date of the oldest known rocks (about 3,800 million years ago); no evidence of life
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    aeon, eon
    the longest division of geological time
    geological period, period
    a unit of geological time during which a system of rocks formed
    era, geological era
    a major division of geological time; an era is usually divided into two or more periods
    a unit of geological time that is a subdivision of a period and is itself divided into ages
    glacial epoch, glacial period, ice age
    any period of time during which glaciers covered a large part of the earth's surface
    type of:
    the continuum of experience in which events pass from the future through the present to the past
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