The geological periods · the Earth has lived 4.6 billion years
What was the Earth like in the Cambrian? And in the Jurassic?
Tap a period. It takes you to the Earth of that time
Where do these periods sit within 4.6 billion years?
The periods above cover only that sliver at the right-hand end. The 88% on the left has hardly any names, because it left no fossils.
- The Earth then
- Life then
The five mass extinctions
Tapping these does not change the map, because they are events the arrangement of the continents does not explain — the end-Permian above all. The maps before and after are almost the same.
The words on this map
Sometimes how a period was worked out is more interesting than memorising its name. How to read rock layers, and where the idea that continents move came from, are in the glossary.
Where this material comes from
- The memory sentence — Lee Jeong-mo, former director of the Gwacheon National Science Museum. He made a Korean sentence whose syllables give the order of the periods, and it became widely known through his talks and broadcasts. The Korean original of this page borrows that sentence as the frame of the map; in this English version the period names stand in its place.
- Arrangement of the continents — Merdith, A.S. et al. (2021) Extending full-plate tectonic models into deep time, Earth-Science Reviews 214, 103477. The plate rotations were computed directly with pyGPlates, and only simplified outlines of the result are shown on this page.
- Boundary ages — the International Chronostratigraphic Chart of the International Commission on Stratigraphy (ICS).
Do not trust the longitudes. This reconstruction rests on palaeomagnetism, the direction of the magnetic field preserved in old rocks. The Earth's field is symmetrical about the axis of rotation, so latitude is recorded but longitude is not. There is evidence, in other words, for 'near the equator or near the pole', and none for 'how many degrees east'. Where the continents sit east to west on this map is a value chosen to look well. Please read only the north-south positions and the gathering and scattering.
Percentage figures for the scale of the extinctions vary widely between sources. That is why this page does not pin them to a single number.
This page turns a list of names into a map. Memorising an order and knowing what that order was about are different things, so here is something to look at once the names are learned.