This unique addition to reference literature provides an introduction to the major concepts and contemporary issues that are essential for students of environmental science and environmental studies to know. With over 200 entries authored by world-class names like Anthony Brazel, John Day and Edward Keller, this text is divided into six sections: Environmental Science, Environments, Paradigms & Concepts, Processes & Dynamics, Scales & Techniques, and Environmental Issues.  

Timescales, Geologic

Timescales, geologic

Geologic time is determined in two senses: absolute and relative. In human terms, absolute time is akin to saying an event happened in the third week of June 2007, plus or minus 2–3 days. Because geologic time is so much vaster than human time, however, radiometric age dating is used to give the absolute age of a rock as, say 175 million years (my) plus or minus 15 my. Relative age, in human terms, is like saying something happened in the latter half of the Ming dynasty. A rock might be said to be Jurassic in age.

Relative Time

The standard geologic timescale The geologic timescale is subdivided into Eras, Periods, Epochs, and Stages, each corresponding to when specific sequences of sedimentary rocks were deposited. ...

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