Fossil Formation Lab: From Seabed to Stone
See that a fossil needs quick burial in quiet, low-oxygen water, that hard parts survive and soft parts rarely do, and that layers stack up in order so depth tells age.
Before you try
What if every animal that ever died became a fossil? How thick would the layer of bones be?
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What happened?
Move a control to see what changes and why.
Burial and decay rates are relative and time is hugely accelerated; real fossilisation takes at least ten thousand years.
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Try these ideas
- Compare the Quiet muddy bay and Lively shallow reef presets with the same fish.
- Try to fossilise a jellyfish. What settings give you anything at all?
- Watch the layers stack up and work out which is oldest.
Why it works
When an animal dies on a seabed, scavengers and rot usually destroy it within weeks. It only has a chance of becoming a fossil if sediment covers it quickly and the water holds little oxygen, so nothing can eat it. Shells and bones survive best; jellyfish and other soft creatures almost never do. Once sealed in, mineral-rich water slowly replaces the bone with stone while the weight of new layers presses the mud into rock.
Because sediment settles layer on layer, a fossil buried deeper is older than one above it. That rule lets geologists read the history of life in cliffs and quarries, from trilobites to dinosaurs. In this lab you choose the creature, the rate at which sediment arrives and the oxygen in the water, then let thousands of years pass and see how much of the animal is preserved.
Check your understanding
Question 1 of 4
Which is most likely to become a fossil?
Why are fossils rare?
In undisturbed layers of rock, the deepest fossil is
A fossil bone is usually
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Press a shell into clay and let it dry: a mould fossil.
- Ask: why do we find sea fossils high in the Himalaya?
- Discuss what a fossil can and cannot tell us about the animal’s colour and behaviour.