One Number, Many Effects: teacher key

Natural Disasters, grade 8 edition, written for 8th grade. A single number can describe an earthquake, a hurricane or a tornado, but it never tells the whole story. See what the numbers measure and what they leave out.

Read the book. Print this page for the key.

Questions and answers

1. About how much more energy does each whole number up in magnitude release?
   • About 32 times (answer)
   • About 2 times
   • About 100 times
2. Why can one earthquake shake two places differently?
   • Shaking varies with distance and type of surface material (answer)
   • It has two magnitudes
   • Seismometers change it
3. What share of tornadoes are weak, rated EF0 or EF1?
   • Under one-tenth
   • About half
   • Over two-thirds (answer)
4. Does opening windows help in a tornado?
   • No, the tornado will blast open the windows anyway (answer)
   • Yes, it equalizes pressure
   • Yes, if done quickly
5. In which direction do hurricanes rotate in the Northern Hemisphere?
   • Clockwise
   • Counterclockwise (answer)
   • Straight
6. What chiefly causes storm surge?
   • Strong onshore winds of a hurricane or tropical storm (answer)
   • The Moon
   • Earthquakes

Words

• magnitude: earthquake size
• supercell: rotating thunderstorm
• Coriolis: spin effect
• surge: pushed water
• aftershocks: later small quakes
• evacuate: leave for safety