The Slip Beneath Us: teacher key

Earthquakes, grade 9 edition, written for 9th grade. Rock under the ground builds up strain and then slips. The shaking runs out in waves. Scientists measure the size, the place and the odds, but they cannot name the day.

Read the book. Print this page for the key.

Questions and answers

1. What does magnitude measure?
   • How strong the shaking is where you stand
   • The size of the earthquake at its source (answer)
   • How deep the ocean is
2. Which waves usually do not shake hard?
   • P-waves (answer)
   • S-waves
   • Surface waves
3. Why did a magnitude 8.3 quake 636 km under Bolivia cause no major damage?
   • It was so deep (answer)
   • It was a small quake
   • It happened in the ocean
4. Which of these could give a real earthquake prediction, as the USGS defines one?
   • A cloud shape and an ache
   • A date and time, a location and a magnitude (answer)
   • A swarm of tiny quakes
5. In this passage, what does inertia explain?
   • Why a mass on a spring stays put when the ground shakes (answer)
   • Why plates are 70 kilometers thick
   • Why tsunamis move fast

Words

• seismograph: shaking recorder
• epicenter: spot above start
• magnitude: quake size
• subduction: plate sinking under
• liquefaction: ground turning soupy