Geologic Timescale of Rathnir and Eldham

The Geologic Timescale is a chart used by geologists and paleontologists to classify the ages of rock formations. As such, its use has been extended to act as a summary of events in deep time, as each period and era has its own specific events and biota unique to it.

For a list of fossil organisms known from each period, refer to the Fossil Taxa list page.

The following chart lists all eras and periods, descending with age. Older strata are generally overlain by younger ones, after all- see the law of superposition.