The Geodynamo and Magnetic Reversals

Lab Brief #6

🎯 Your mission

Learn the rule. Then catch nature using it.

⚡ The twist

Weather isn't random — it's just complicated.

What you'll learn

Earth's magnetic field is not produced by a permanent magnet — iron loses its magnetism far below core temperatures. It is generated by convecting liquid iron in the outer core, a self-sustaining geodynamo. The field has reversed hundreds of times, and because basalt erupting at a mid-ocean ridge locks in the field direction of the day it cooled, the sea floor carries symmetrical magnetic stripes. Those stripes both date the crust and independently prove it is spreading.

Key words

geodynamo
The process by which convecting liquid iron in the outer core generates Earth's magnetic field.
magnetic reversal
A flip of Earth's magnetic poles, recorded as a stripe of oppositely magnetised rock in the sea floor.

Make a hypothesis first

Before you observe: what shape will it leave?

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

Step 1 of 4 · Read

Think about what you just learned: say what "geodynamo" and "magnetic reversal" mean in your own words before you start.

Step 2 of 4 · Do

Map the magnetic stripe pattern from a survey printout either side of a ridge, colouring normal and reversed bands. Measure the width of each band, and use the known reversal dates to work out the spreading rate.

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

Earth's magnetic field is generated by:

How sure are you?😐 maybe

Question 2 of 3

Magnetic stripes on the sea floor record:

How sure are you?😐 maybe

Question 3 of 3

A permanent magnet could not produce Earth's field because iron at core temperatures:

How sure are you?😐 maybe

Mind = blown

🌊 The deepest part of the ocean is deeper than Mount Everest is tall.

Nice work!

You got 0 of 3 right.

Next: Relative and Absolute Dating Together 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: This is shaping the ground you walk on, slowly, every single day.

🏆 Stretch challenge (try it this week): Find a rock outside and try to guess how old it is.

👨‍👩‍👧 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.

The Geodynamo and Magnetic Reversals

Next Smart Experiment

Share this experiment

The Geodynamo and Magnetic Reversals

Done with science? Try something else

Your Cart (0)