File:Geological time spiral.png

This image was selected as picture of the day on Wikimedia Commons for 11 June 2009. It was captioned as follows: English: A diagram of the geological time scale Other languages:  Česky: Schématické znázornění geologické časové škály Dansk: Diagram over Jordens geologiske tidsperioder Deutsch: Visuelle Darstellung der Erdzeitalter als Zeitspirale mit englischer Beschriftung (eine deutsche Version der Grafik ist derzeit nicht vorhanden) English: A diagram of the geological time scale Español: Diagrama de la escala de tiempo geológica Français : Diagramme de l' échelle des temps géologiques. עברית: דיאגרמה של סקאלת זמן גיאולוגי Magyar: A geológiai időskála szemléltetése Bahasa Indonesia: Diagram skala waktu geologi yang berbentuk spiral Italiano: Diagramma della scala dei tempi geologici. 日本語: ら旋状の 地質学年表 한국어: 지질학적 연대표. Македонски: Приказ на геолошките периоди Nederlands: Engelstalige visuele presentatie van de geologische tijdschaal in de vorm van een spiraal Polski: Diagram przedstawiający skalę czasu geologicznego. Português: Um diagrama ( em inglês) da escala de tempo geológico. Română: Diagramă a istoriei geologice a Pământului Русский: Геохронологическая шкала, изображённая в виде спирали Slovenščina: Diagram geoloških dob (napisi v angleščini) Українська: Геохронологічна шкала, зображена у вигляді спіралі 中文（简体）‎: 地质学时标图 中文（繁體）‎: 地質學時標圖

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Summary

Caption

Original source: http://pubs.usgs.gov/gip/2008/58/geotimespiral_text.pdf

The Earth is very old—4.5 billion years or more according to scientific estimates. Most of the evidence for an ancient Earth is contained in the rocks that form the Earth's crust. The rock layers themselves—like pages in a long and complicated history—record the events of the past, and buried within them are the remains of life—the plants and animals that evolved from organic structures that existed 3 billion years ago.

Also contained in rocks once molten are radioactive elements whose isotopes provide Earth with an atomic clock. Within these rocks, "parent" isotopes decay at a predictable rate to form "daughter" isotopes. By determining the relative amounts of parent and daughter isotopes, the age of these rocks can be calculated. Thus, the scientific evidence from rock layers, from fossils, and from the ages of rocks as measured by atomic clocks attests to a very old Earth.

See USGS Fact Sheet 2007-3015 at http://pubs.usgs.gov/fs/2007/3015/ for ages of geologic time periods. Ages in the spiral have been rounded from the age estimates in the Fact Sheet. B.Y., billion years; M.Y., million years. For more information, see the booklet on Geologic Time at http://pubs.usgs.gov/gip/geotime/.

Licensing

This image is in the public domain because it contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior. For more information, see the official USGS copyright policy. български | català | Deutsch | English | español | eesti | suomi | français | galego | italiano | 한국어 | македонски | മലയാളം | Nederlands | polski | português | русский | Türkçe | 中文 | 中文（简体）‎ | +/−

The following pages on Schools Wikipedia link to this image (list may be incomplete):

• Geologic time scale
• Givetian