EARTH × TECHNOLOGY

Naming the Chapters

1815 to today

Phanerozoic · Cenozoic · Quaternary · Holocene · Meghalayan

Cambrian, Jurassic, Cretaceous: the names on the strip below this timeline were coined one at a time, from a Welsh tribe, a French mountain range and English chalk, by people who could put the layers in order long before they could put a number on any of them. What made the ordering possible was the discovery that each layer carries its own fossils, and always the same ones.

Why it matters

It is the shared vocabulary that lets a fossil dug up anywhere on Earth be placed in one story, and the coloured column on this page is made of it. The boundaries still move as dating improves, which is worth remembering: the chapters are a convention, agreed on and revised, laid over a record that has no chapters in it.

Dating & uncertainty

The first geological map of a whole country appeared in 1815, built on the discovery that each layer carries its own fossils. The periods were named across the nineteenth century, and their boundaries are still being moved as dating improves.

Sources

1. Wood (2019), Time's Urgency · Petrotemporality at Siccar Point: James Hutton's deep time narrative
2. Witze (2024), Nature · It's final: the Anthropocene is not an epoch, despite protest over vote

Earth history as one day

23:59:59.99604.0 ms before midnight

if Earth’s 4.54 billion years were compressed into a single day