How earthquake waves reveal Earth's interior
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
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
- S waves pass through the core and show it is solid
- Earthquake wave paths and speeds reveal the layers
- Correct; drilling is the one way to know
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 bounce off the Moho before they reach the core
- P waves cross the core but bend, missing 104° to 140°
- Correct; P waves cannot enter the core
- The shadow comes from S waves arriving first
Read this first
Model speeds
Wave Speed P 6 km/s S 3.5 km/s A station records a 30 s lag. Using the model speeds, about how far is the quake, by Milo's math?
- About 252 km
- About 30 km
- About 180 km
- About 105 km
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.
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 15 km
- About 90 km
- About 126 km
- About 294 km
How do scientists know the inner core is solid, by Pia's reading (USGS)?
- From drill samples of the inner core
- From how P and S waves behave passing through it
- S waves are stopped at the inner core's edge
- Its waves travel at one steady speed
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?
- Density has no link to the core
- The extra density comes from the oceans
- The core is lighter than surface rock, which lowers the average
- A dense, mostly iron core explains the high average density
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
- The Moho speed jump comes at a shallower depth under the ocean
- S waves vanish under the ocean
- Waves keep one speed under both
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
- P arrives first and crosses liquid; S is slower and stops at liquid
- Both cross liquid at the same speed
- P is slower and stops at liquid
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 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
- Thin crust, liquid mantle, solid outer core
- Thick crust, thin mantle, solid outer core, liquid inner core
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
- Check whether P waves are stopped there
- Measure the planet's surface heat by itself
- Check whether S waves cross it and whether P waves slow there
