Lesson 7 of 8 · Earth Systems

Experiment⭐ 30 XP🌋 Rock Realm

Relative and Absolute Dating Together

Lab Brief #7

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

Today's mountain was yesterday's ocean floor.

What you'll learn · 1 of 2

Relative dating orders events without numbers: a layer is younger than the one beneath it, and an intrusion is younger than everything it cuts through. Absolute dating puts years on those events using radioactive decay — with a known half-life, the ratio of parent to daughter isotope in a mineral gives its age directly. Neither is sufficient alone: relative dating gives sequence without dates, absolute dating gives dates for igneous rock but not for the sedimentary layers around it.

What you'll learn · 2 of 2

Combining them is what turns a cliff face into a 4. 6-billion-year timeline.

Key words

relative dating
Placing rock layers and events in order without assigning them numerical ages.
half-life
The time taken for half the atoms of a radioactive isotope in a sample to decay.

Make a hypothesis first

Guess: where will the water go first?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

100 coins
tray
graph paper
calculator

⚠️ Safety first

Small coins are a choking hazard — keep them away from young children, and wash your hands afterwards.

Step 1 of 4 · Read

Think about what you just learned: say what "relative dating" and "half-life" mean in your own words before you start.

Step 2 of 4 · Do

Model decay by shaking 100 coins in a tray, removing every coin that lands heads, and recording the number left after each shake. Plot the count against shake number, read off your model's half-life, and explain what the coins stand for.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 3

An igneous intrusion cutting through three layers must be:

How sure are you?😐 maybe

Question 2 of 3

Absolute dating of a mineral uses the ratio of:

How sure are you?😐 maybe

Question 3 of 3

After two half-lives, the fraction of the original isotope remaining is:

How sure are you?😐 maybe

Mind = blown

🌋 There are 1,500 active volcanoes on Earth right now.

Nice work!

You got 0 of 3 right.

Next: Carbon Fluxes and the Small One-Way Addition All lessons

🎯

Next Smart Experiment

We'll pick an experiment that matches exactly how you're thinking right now.

✨ More to explore

🌍 Where you see this in real life: Today's weather, tomorrow's beach, next century's coastline — all this.

🏆 Stretch challenge (try it this week): Look at the sky for 5 minutes and try to predict tomorrow's weather.

👨‍👩‍👧 For the dinner table: “What's the slowest change you can think of?”

🌎Share card

Share this experiment

Send it to a parent who's looking for a 10-minute kitchen science win.

Relative and Absolute Dating Together

Next Smart Experiment

Share this experiment

Relative and Absolute Dating Together

Done with science? Try something else

Your Cart (0)