Seismic Waves & Earth's Interior · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Seismic Waves and Earth's Hidden Layers

Science · Volcanoes & Earthquakes · ages 11-13
Name ______________________   Date ____________

  1. Which wave type cannot pass through Earth's liquid outer core at all?

    • P-wave
    • S-wave
    • Neither wave is blocked

  2. Which kind of wave squeezes and stretches rock as it travels, like pushing and pulling a spring?

    • P-wave
    • S-wave
    • Both move the same way

  3. At a nearby station that receives both P-waves and S-waves from the same earthquake, P-waves arrive first.

    Circle one:   True   False

  4. Why is there a broad shadow with no direct S-waves on the far side of Earth from an earthquake?

    • The liquid outer core blocks S-waves
    • S-waves travel only through the air
    • The crust stops both types of wave

  5. Consider waves that keep their type along their path. At the opposite side of Earth from an earthquake, which can arrive through the core?

    • Direct S-waves, but no P-waves
    • Both direct S-waves and P-waves
    • P-waves, but no direct S-waves

  6. Scientists notice P-waves bend sharply as they cross from the mantle into the outer core. What does that bending tell them?

    • The P-waves are lost and never continue
    • The material changes at a layer boundary
    • The mantle and outer core are made of the exact same material

  7. In Earth's wave model, P-waves slow on entering the liquid outer core, then speed up at a deeper boundary. Which layer do they enter there?

    • Earth's solid inner core
    • The waves bounced back and reached the crust again
    • The earthquake itself grew stronger at that depth

  8. A classmate says, 'A P-wave crossed Earth's core, so the whole core must be solid.' Why does that conclusion not follow?

    • P-waves cannot travel through liquid
    • P-waves travel only through the crust
    • P-waves cross both solids and liquids
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Seismic Waves and Earth's Hidden Layers W1-mt__kFxuAgs6d-s1

  1. S-wave · S-waves need a solid to carry their shear motion. Earth's outer core is liquid metal.
  2. P-wave · P-waves compress and stretch rock as they travel, which is why they're called compression waves.
  3. True · P-waves travel faster than S-waves through the rock between the earthquake and this station.
  4. The liquid outer core blocks S-waves · S-waves can only move through solids, so the liquid outer core stops them from reaching the far side.
  5. P-waves, but no direct S-waves · P-waves can travel through the core. Direct S-waves cannot cross its liquid outer layer.
  6. The material changes at a layer boundary · A change in wave speed at a material boundary can bend the wave's path. This is refraction.
  7. Earth's solid inner core · The model places the solid inner core inside the liquid outer core. P-waves speed up at this boundary.
  8. P-waves cross both solids and liquids · A P-wave can cross a liquid as well as a solid. Its arrival alone cannot show that the whole core is solid.
Worksheet · LightMySky