When the Poles Swap: teacher key

Magnets, grade 10 edition, written for 10th grade. How magnets work from the inside, why Earth has a field, and what pole reversals do.

Read the book. Print this page for the key.

Questions and answers

What happens during a pole reversal?
- The Sun goes dark
- Earth's magnetic north and south poles swap locations (answer)
- Earth stops spinning
When did Earth's field last reverse?
- About 750,000 to 780,000 years ago (answer)
- Last year
- About 100 years ago
How long would it take a reversal to complete?
- A single day
- Several thousand years (answer)
- Ten minutes
What do the fossils from the last major reversal show?
- No big changes (answer)
- Mass extinction
- New seas
Which two facts together suggest a pole reversal would not be a sudden disaster?
- It would take several thousand years, and fossils from the last one show no big changes (answer)
- The field vanishes, and compasses stop
- Reversals are rare, and the Sun goes dark