Nature · Earth Science
Reading the deep history of life in stone
Fossils are the preserved remains or traces of ancient life, sealed in rock and revealed by erosion or excavation. Stacked layer by layer, they let geologists read the vast story of life and time — the geologic timescale — stretching back billions of years and marked by great bursts of life and mass extinctions.
Fossilisation is rare and demands quick burial. When an organism is covered by sediment before it decays, minerals gradually replace its tissues or fill its mould, turning it to stone. Younger fossils lie in higher layers, so the sequence of strata becomes a calendar of Earth’s past.
Sediment buries remains layer upon layer — the deeper the rock, the older the fossils and the era they record.
The remains turned to stone
Body fossils are mineralised remains of the organism itself — bones, shells, teeth or petrified wood. Slow mineral replacement can preserve astonishing anatomical detail.
Frozen evidence of behaviour
Trace fossils capture behaviour rather than bodies — a dinosaur’s footprints, a worm’s burrow, a nest. They reveal how extinct creatures moved, hunted and lived.
Nature’s timestamps
Some species lived briefly but spread worldwide, so their fossils pin a rock layer to a precise slice of time. Ammonites and trilobites are prized index fossils for dating strata.
Life captured almost intact
Rarely, an organism is preserved almost whole — an insect sealed in amber, a mammoth frozen in permafrost, animals trapped in tar. These give us the closest look at vanished life.