Last week we looked at the timeline of Earth’s history, this week we’re back on the 'educational' track to answer an important question: how does something actually turn into a fossil?
(I’ll be alternating these educational posts with more creature-specific “Fossils in Focus” posts, so next week I'll go back to focusing on an ancient superstar!)
Not every bone, shell, or leaf gets preserved — in fact, fossilisation is really rare, but when it does happen, the most well know type is a body fossil — the remains of the actual organism itself. So let's just go over how this transformation happens.
1 - Death & Burial – The animal dies, and instead of being scavenged or weathered away, its remains get quickly buried by sediment — mud, sand, or silt. This protects it from decay.
2 - Sediment Build-Up – More layers of sediment pile on top, pressing down and helping preserve the shape of the bones or shell.
3 - Mineral Replacement – Over time, groundwater carrying minerals seeps into the buried remains. The organic material slowly dissolves and is replaced by stone, keeping the fine details intact. This is called Petrification.
4 - Rock Solid – Millions of years later, you’re left with a fossil: the original creature l(or wood), now preserved as stone. Eventually erosion like the cliffs along the Jurassic coast, or excavation, brings it back to the surface.
5 - Discovery – The newly discovered fossil is the ready to be studied, or simply admired in a collection.
This week’s sketch shows that process step by step, so you can see how a once-living creature ends up as a fossil locked in stone.
Fun fact: Different minerals can replace the original material during fossilisation, which is why fossils can take on different colours and appearance, from jet-black to sandy brown to even Opalised (yup, rare but awesome!)
