Time Scales

Rock Engineering

Radiometric Methods

Outline

The geologic time scale was originally a set of relative dates but the various eons, eras, periods and epochs have now been accurately dated with the aid of radiometric methods.

The important dates are:

4,600 My - the age of the Earth and Solar System
3,600 My - the earliest life
570 My - the first appearance of abundant and varied organic forms
200 My - the break-up of the super continent Pangea
66 My - the disappearance of the dinosaurs

The geologic time scale is usually presented in a distorted form - 87% of the total time span is represented by the Proterozoic and Archean eons of the Precambrian. Many geologists and engineers like to visualize the scale in a more familiar guise:

Rock Engineering

Radiometric Methods

Outline

(c) Department of Civil and Geological Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, Canada, S7N 5A9