Fossil Formation & Geological Time Simulator
Bury an organism and control burial depth, oxygen exposure and time to see it fossilize through compaction and mineral replacement, then read the sediment layers using relative dating.
How to use: set burial depth, sedimentation rate, oxygen exposure, pressure and temperature, then move the geological time slider forward to watch the organism pass through burial, compaction and mineral replacement. Check the Relative dating and Challenge tabs.
Relative dating & index fossils
The Law of Superposition says older layers lie below younger ones (unless disturbed). Your fossil sits in the layer that formed when it was buried, so every layer above it is younger and every layer below it is older. A widespread, short-lived species (an index fossil) found in the same layer at different sites lets geologists match the age of rocks far apart.
Challenge 1: maximize preservation
Tune the controls (low oxygen, fast/deep burial) to get the preservation chance to 90% or higher.
Challenge 2: reach the mineral-replacement stage
Move the geological time slider so the fossil reaches stage 4, Mineral replacement (15–30 Myr), without going all the way to a complete fossil.
About the Fossil Formation & Geological Time Simulator
Free fossil formation & geological time simulator. Bury an organism and control burial depth, oxygen exposure and time to see it fossilize through compaction and mineral replacement, then read the sediment layers using relative dating. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for geology, the fossil formation & geological time simulator runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Bury an organism and control burial depth, oxygen exposure and time to see it fossilize through compaction and mineral replacement, then read the sediment layers using relative dating. Use it to explore geology ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Fossil Formation & Geological Time Simulator
- Use the controls to change Burial depth, Sedimentation rate, Oxygen exposure, Pressure, Temperature, and more. The simulation reacts instantly.
- Press "Bury a new organism", "Reset to defaults", "📄 Lab Report" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Set oxygen exposure low and burial depth high, then advance time to watch the preservation chance rise.
- Advance geological time and watch new sediment layers stack up above the fossil layer.
- Compare a slow, oxygen-rich burial to a fast, low-oxygen one.
- Open the relative dating panel and read off which layers are older and younger than the fossil.
Key ideas you can learn
- Low oxygen slows decay, which is why anoxic mud, tar and amber preserve fossils so well.
- Fast, deep burial protects remains from scavengers and weathering before fossilization can begin.
- Permineralization replaces original material with minerals from groundwater, molecule by molecule.
- The Law of Superposition says older sediment layers lie below younger ones, letting geologists read relative age directly from the rock.
Where this is used in the real world
Paleontologists use these same burial and preservation principles, plus superposition, to build the geological time scale and reconstruct ancient environments.
Who is this simulation for?
Students, teachers and curious learners of all ages.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is an index fossil?
A fossil species that lived briefly but spread widely, so finding it in rock layers at different locations lets geologists match those layers to the same age.
Why do some organisms fossilize and others don't?
Fossilization needs quick burial and low decay conditions; most organisms simply decompose completely before any of this can happen.
Is the Fossil Formation & Geological Time Simulator free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Fossil Formation & Geological Time Simulator work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.