SIC-Forming Fossils

Forming Fossils

DEAR SCIENCE WORLD,

Are the fossils real in your feature exhibition Fossils, Fins and Fangs: Dinosaurs and Other Ancient Life?

Fossilized

Dear Fossilized,

Yes, we’re proud to say that those are real fossils and they’re rarer than you think. Many museums make casts of fossils rather than displaying the real thing—real fossils are rare, heavy and breakable.

Museums all over the world have thousands of fossils, but billions of creatures have lived on Earth, making the percentage of creatures that end up as fossils pretty small.

So what does it take to make a fossil?

Let’s talk about death for a bit first. When animals or plants die, scavengers usually devour their remains. What the scavengers don’t get—like bones—bacteria and the weather usually take care of.

Sometimes though, an animal will die near or in water, protecting its remains from being eaten or destroyed. Bacteria still consume the soft parts of the body but leave behind the hard bones and teeth.

If palaeontologists are really lucky, the animal will be buried quickly after death, like in a mudslide, protecting it from the elements even more. This means no scavengers can get to it and the remains stay nice and cosy while surrounded by sediment, like a cocoon.

However, water with minerals can still work its way through the sediment. Though bones seem solid, there are actually thousands of little holes in them. The minerals will settle in the holes and stay there. As water creeps into the sediment, bits of bone and teeth start to dissolve, leaving minerals in their place. This is called permineralization.

At the same time, increasing sediment weight from above crushes the earth surrounding the remains, turning sediment into rock. When the remains eventually fully dissolve, the minerals have replaced the bone and glued together into rock, leaving a fossil behind.

With some fossils, called mould fossils, an animal gets buried and starts to erode and dissolve while the earth around it hardens. It’s kind of like when a balloon pops inside paper mâche.

Another kind of fossil works like a stamp. Plants and soft body parts of fish and reptiles decompose, leaving behind carbon residue. The carbon leaves a perfect impression of the plant or animal in the rock, like a stamped picture

If things don’t happen exactly right—a scavenger gets to the remains first or weather erodes everything away, a fossil doesn’t form.

So yes, the fossils in our exhibition are real and we’re excited to be able to share them with you. After all, it’s not every day that you can touch a real fossil that dates back millions of years.

Fossil Hunter, Sam Digg