Relative dating means deciding older and younger. First build the model’s rock layers from bottom to top. Then add a fault or a body of once-molten rock called an intrusion. A cutting feature must be younger than the material it cuts, even if its colour looks similar to an older layer.
Earth and geology · Discover & try
What happened first in these rock layers?
Reading level 2 of 5 · DevelopingChange
Word help
Superposition
In an upright undisturbed stack, lower sedimentary layers are older.
Intrusion
Rock formed when magma enters and solidifies within existing material.
Cross-cutting relationship
A feature is younger than the material it cuts.
Watch · Try · Explain
See how it works
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Original upright-layer reconstruction; no real outcrop dates, overturned beds or missing-time estimates are implied.
What to look for
- Build the bottom layer first.
- Check which layers a feature actually cuts.
- Keep event order separate from elapsed years.
Explain what you noticed
In another outcrop, a fault cuts beds M and N, but an undisturbed bed P covers the fault. Which sequence fits?
Keep this idea: Relative dating puts events in order without assigning ages in years.
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Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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