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
   • Correct; drilling is the one way to know
   • Drill holes have reached the core
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; 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
   • Correct; P waves speed up 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?

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

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 9.5 km
   • About 2.5 km
   • About 1.7 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 180 km
   • About 30 km
   • About 252 km
7. 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 drill samples of the inner core
   • From how P and S waves behave passing through it
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.

   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
   • P is slower and stops at liquid
   • S arrives first and crosses liquid; P stops at liquid

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
    • Thick crust, thin mantle, solid outer core, liquid inner core
    • Thin crust, thick mantle, liquid outer core, solid inner core
    • Thin crust, liquid mantle, solid outer 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?

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