Measuring the Extremes: teacher key

The Arctic and Antarctica, grade 11 edition, written for 11th grade. How thick is sea ice, how cold is Antarctica and how do you study a seal that moves every year? See how polar scientists measure what is hard to reach.

Read the book. Print this page for the key.

Questions and answers

1. Why is sea ice thickness hard to measure?
   • Sea ice has no thickness
   • No current technology measures it directly and continuously over a broad area (answer)
   • It is always moving south
2. What does sonar measure when used on sea ice?
   • The distance to the ice above, from an echo's travel time (answer)
   • The temperature
   • The salt content
3. What is the lowest temperature recorded in Antarctica by satellite?
   • -20 degrees Celsius
   • -89.2 degrees Celsius
   • -93.2 degrees Celsius (answer)
4. Why does each seal tag last only until the molt?
   • Tags run out of power
   • Seals shed their fur each year (answer)
   • Seals swim too deep
5. What causes auroras?
   • The solar wind meeting Earth's magnetic field (answer)
   • Ice crystals
   • Volcanoes

Words

• altimeter: height gauge
• sonar: sound ranging
• aurora: sky lights
• magnetosphere: magnetic bubble