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?

   • Earthquake wave paths and speeds reveal the layers
   • S waves pass through the core and show it is solid
   • Drill holes have reached the core
   • Correct; drilling is the one way to know
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
   • It is gas, since waves vanish there
   • S waves do not cross it and P waves slow there, so it is liquid
   • Correct; S waves cross it easily, so it behaves like a solid rock
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?

   • P waves cross the core but bend, missing 104° to 140°
   • The shadow comes from S waves arriving first
   • Correct; P waves cannot enter the core
   • 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. 5.

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

   • About 105 km
   • About 30 km
   • About 180 km
   • About 252 km
7. 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
   • From how P and S waves behave passing through it
   • Its waves travel at one steady speed
8. 7.

   Newton found Earth's average density is twice that of surface rocks (USGS). How did the core's discovery fit this, by Ren's reading?

   • The core is lighter than surface rock, which lowers the average
   • The extra density comes from the oceans
   • A dense, mostly iron core explains the high average density
   • Density has no link to the core
9. 8.

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

10. 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

11. 9.

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

    • Solid core throughout, since S waves cross it
    • Thin crust, thick mantle, liquid outer core, solid inner core
    • Thin crust, liquid mantle, solid outer core
    • Thick crust, thin mantle, solid outer core, liquid inner core
12. 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?

    • Count how many quakes happen
    • 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