He is of opinion that in some geological era the whole place has been formed in a salt-water lake.

This summary statement will convey some idea of the extraordinary phase through which the earth passed in the early part of the present geological era.

We'll have to dump it when we dock, it's got a half-life longer than some geological eras now.

It altered and adapted over geological eras, slowly learning to utilize the two contrasting light sources as an additional energy supply.

Since nobody had ever bothered to study extinction in an organized way, there was little information about rates of extinction in other geological eras.