How earthquake waves reveal Earth's interior

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   A student says the outer core must be solid because it is under great pressure. Which reply fits USGS, by Jun's reading?

   • Correct; P waves speed up there
   • Correct; S waves cross it easily, so it behaves like a solid rock
   • S waves do not cross it and P waves slow there, so it is liquid
   • It is gas, since waves vanish there
2. 2.

   Earth cutaway with a shaded band. A student says the P shadow zone shows the core blocks P waves. Which reply fits USGS, by Kira's reading?

   • P waves cross the core but bend, missing 104° to 140°
   • Correct; P waves cannot enter the core
   • Correct; P waves bounce off the Moho before they reach the core
   • The shadow comes from S waves arriving first

3. Read this first

   Model speeds

   Wave	Speed
   P	6 km/s
   S	3.5 km/s

4. 3.

   With model speeds P 6 km/s and S 3.5 km/s, the lag grows by 1 second for about every how many km, by Luz's math?

   • About 8.4 km
   • About 1.7 km
   • About 2.5 km
   • About 9.5 km
5. 4.

   A station records a 30 s lag. Using the model speeds, about how far is the quake, by Milo's math?

   • About 180 km
   • About 105 km
   • About 252 km
   • About 30 km

6. Table, Model lag table, with columns Lag, Distance

   10 s, 84 km; 25 s, 210 km; 50 s, 420 km. Note: model speeds P 6 km/s, S 3.5 km/s.

7. 5.

   Two stations record lags of 10 s and 25 s from one quake. Using the model lag table, how much farther is the second, by Noah's math?

   • About 126 km
   • About 294 km
   • About 90 km
   • About 15 km
8. 6.

   How do scientists know the inner core is solid, by Pia's reading (USGS)?

   • S waves are stopped at the inner core's edge
   • From drill samples of the inner core
   • Its waves travel at one steady speed
   • From how P and S waves behave passing through it
9. 7.

   USGS: oceanic crust at Hawaii is about 5 km thick; continental crust in eastern California is 25 to 60 km. Which wave data would show this, by Tala's reading?

   • Waves keep one speed under both
   • The Moho speed jump comes at a shallower depth under the ocean
   • S waves vanish under the ocean
   • The Moho speed jump comes deeper under the ocean
10. 8.

    a first wave, then a second. Which summary of P and S waves fits USGS, by Zee's reading?

    • S arrives first and crosses liquid; P stops at liquid
    • Both cross liquid at the same speed
    • P is slower and stops at liquid
    • P arrives first and crosses liquid; S is slower and stops at liquid

11. Data on the Earth's interior (USGS)

    Layer	Thickness
    crust	30 km
    upper mantle	720 km
    lower mantle	2,171 km
    outer core	2,259 km
    inner core	1,221 km

12. 9.

    Which summary of Earth's interior from wave data fits USGS, by Ari's reading?

    • Thin crust, thick mantle, liquid outer core, solid inner core
    • Solid core throughout, since S waves cross it
    • Thick crust, thin mantle, solid outer core, liquid inner core
    • Thin crust, liquid mantle, solid outer core
13. 10.

    Four plan cards, labeled A to D. Which plan best tests whether a layer deep inside a model planet is liquid, by Bo's reading?

    • Measure the planet's surface heat by itself
    • Check whether S waves cross it and whether P waves slow there
    • Check whether P waves are stopped there
    • Count how many quakes happen