Democratic Sentinel, Volume 7, Number 33, Rensselaer, Jasper County, 14 September 1883 — Geological Divisions of Time. [ARTICLE]

Geological Divisions of Time.

The divisions of time established by geologists are based upon the formations of strata and the advents of different forms of animal life. The history of the earth is divided into five “eras,” seven “ages,” twenty-two “periods,” and the last two periods are subdivided into seven epochs. These divisions, proceeding from the fifth downward to the first, are as follows: 5. Psychozoic era, age of man, human period and recent epoch. 4. Cenozoic era, age of mammals—embracing the quaternary period, which comprehends the terrace, Champlain and glacial epochs, and the tertiary periods, which comprehends the pliocene, miocene and eocene epochs. 3. Mesozoic, or middle era, the age of reptile, the cretaceous, jurassic and triassic periods. 2. Paleozoic era, the carboniferous age, or age pf acrogens and amphibians; the Devonian age, or age of fishes; the silurian age, or age of invertebrates, or mollusks — the names of the fourteen periods into which these ages are divided are not in common use. 1. Archaean, or eozoic era; the archaean age, and the Huronian and Laurentian periods. For an explanation of the terms used in this division consult Webster’s or Worcester’s Unabridged Dictionaries, and study the clear illustration accompanying the word “Geology” in the former work.