Earth Geology Geologic History Relative Time Scale

This geological time scale is based upon Harland et al., 1990. The time scale is depicted in its traditional form with oldest at the bottom and youngest at the top -- the present day is at the zero mark. Because of the vast difference in scale, the younger intervals have been successively expanded to the right to show some of these finer subdivisions. 

Source: Harland, W.B.; Armstrong, R.L.; Cox, A.V.; Craig, L.E.; Smith, A.G.; and Smith, D.G., 1990. A geologic time scale, 1989 edition. Cambridge University Press: Cambridge, p.1-263. ISBN 0-521-38765-5 [One of the more recent compilations of the entire geologic time scale.] This image is provided by Andrew MacRae at The University of Calgary, Dept. of Geology and Geophysics.