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The Geological Timescale

Geoscientists use a timescale to study the history of the Earth and its life.

Download this wall chart of the Geological Timescale: Timescale_Card_2015_poster.pdf (50.75 kB)

Slow processes, such as the erosion of mountains, movements of tectonic plates and the evolution of life on Earth can only be fully appreciated against the vastness of geological time. This is a difficult concept to envisage, even for geoscientists! To find out how scientists measure geological time click here.

The timescale has three main subdivisions called ‘Eons’ going back to the earliest of known rocks: The ‘Age’ column shows “millions of years” before present: It is shown with the youngest rocks at the top and the oldest at the bottom, just like rock sequences are usually found in the field (see Superposition).

Geological timescale 1

Phanerozoic means “visible’ or “revealed life” This Eon extends back to 542 million years when many large life forms such as molluscs and trilobites first appeared in the fossil record. There are no known rocks of Archean or Proterozoic age within Zealandia (the New Zealand continent), but rocks of these ages are known in neighbouring Australia and Antarctica.

The main units of the Phanerozoic are shown in this table, which covers the age span of New Zealand geology:

Geological timescale 2

For more on the Geological Timescale click here