How earthquake waves reveal Earth's interior

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   A classmate says no one knows what is inside Earth because no one has drilled there. Which reply fits USGS, by Esme's reading?

   • Drill holes have reached the core
   • Earthquake wave paths and speeds reveal the layers
   • Correct; drilling is the one way to know
   • S waves pass through the core and show it is solid
2. 2.

   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
3. 3.

   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?

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

4. Read this first

   Model speeds

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

5. 4.

   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

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

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

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

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

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

    • Both cross liquid at the same speed
    • P arrives first and crosses liquid; S is slower and stops at liquid
    • S arrives first and crosses liquid; P stops at liquid
    • P 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, liquid mantle, solid outer core
    • Solid core throughout, since S waves cross it
    • Thin crust, thick mantle, liquid outer core, solid inner core
    • Thick crust, thin mantle, solid outer core, liquid inner 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
    • Count how many quakes happen
    • Check whether P waves are stopped there