LOSTBONE JUNGLE · DINOLING
Rock Layers & Relative Time
Tar Pit Terrace
Learn with Dinoling, then use your clues in the adventure. Pause whenever you need time to read or think.
Speech bubbles tell the story. Music and sound effects are optional; use the player’s volume control.
Your Tar Pit Terrace adventure
Train more: lesson transcript and free resources
Dinoling — Rock Layers & Relative Time Tar Pit Terrace
Dinoling here. Welcome to our imaginary Tar Pit Terrace station.
The Grumblies scrambled our layer labels. Let's study our model.
Our lesson uses sedimentary layers, not a tar-deposit timing rule.
Sediment can collect in layers, with new material above older material.
Our model shows a simple stack that hasn't been overturned.
In this model, the bottom layer was deposited first.
The next layer collected above that earlier layer.
The top layer collected last in our three-layer example.
We can compare which layers are older and younger.
This comparison is called relative age.
It doesn't give an exact number of years by itself.
Think of knowing which sibling is older without knowing birthdays.
That comparison gives an order, but not an exact age.
Our model labels the bottom layer A.
The middle layer is B, above A and below C.
The top layer is C.
A is oldest. B came next. C is youngest here.
Fossils found in layers add evidence about past life.
Recording the layer helps preserve context for each discovery.
That's why I never leave the layer label out of notes.
Real rock layers may be tilted, folded, broken, or overturned.
Erosion can also remove parts of an earlier record.
Scientists investigate these changes before interpreting the order.
Our simple model works because we know its layers are undisturbed.
The Grumblies want us to ignore that condition. We won't!
In our undisturbed model, which layer is oldest: A or C?
A sits below B and C. Think about what arrived first.
A! It was deposited before the layers above it.
Good observing. You used the model's stated conditions.
Does 'A is older than C' tell us A's exact age?
No. It gives relative age, not an exact number of years.
In a simple undisturbed stack, lower layers are older.
Relative age means older or younger, not exact years.
Real records may have missing or disturbed layers.
Our model labels are restored. My notebook has the conditions, too.
Keep those details with you as we investigate the adventure.
Train more, start this adventure, or choose another map destination.
Free Rock Layers & Relative Time teacher guide and practice (PDF)
Explore any of the six lessons
Every destination is open. No account, purchase, previous lesson, or completed video is required.