How are fossils formed?

For a plant or animal to become a fossil, a series of events must occur...

From dinosaur to fossil: stage 1

 © Australian Museum

The remains have to be buried before they completely decompose or are eaten. The conditions of burial must then be suitable for the remains to leave an impression or have their organic material replaced by minerals. Finally, the fossils must survive millions of years of pressure, uplift and erosion if they are to come back to the surface.

So what are the chances of any dead animal turning into a fossil? Many millions to one – so we certainly appreciate the fossils we find.

From dinosaur to fossil

Stage 1

A dinosaur dies and is buried before the remains are completely destroyed.

Stage 2

Over time, layers of sediment build up and press down on the buried remains.

Stage 3

Dissolved minerals, transported by ground-waters in the sediment, fill tiny spaces in the bones. The combination of pressure, chemical reactions and time eventually turns the sediments into rock and the bones into mineralised fossils.

Stage 4

The fossils remain within the rock until uncovered through erosion or excavation.


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Tags fossils, formation, sedimentation, fossilisation, fossilization, palaeontology,