The atlas · Back through time
Geological time
How deep time is measured, named and dated.
3 written · 6 in outline · 3 sections
The timescale
- The timescale
The whole international chart of geological time, eons to epochs, with the age of every boundary.
- The Walk
The age of the Earth laid out as a walk, so you can feel how long deep time is.
- Where the names come from
Where each period’s name comes from, and the places they are named after.
Reading layers
- The rules of layers
The simple rules for reading layers of rock in order, and the tricks that fool them.
- Golden spikes
How each boundary on the chart is fixed to one spot in one rock face.
Dating
- How old is the Earth?
Atoms that fall apart at a steady rate are the clocks. Read them right and the answer is 4.54 billion years.
- How radioactive clocks work
How the steady decay of atoms is used to put an age in years on a rock.
- Dating rock by its fossils
How fossils that lived briefly but widely let geologists match the age of rocks across the world.
- Ways of dating rock
Each dating method, what it can date and how far back it reaches.