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Science lesson plan · 10th grade (Year 11 in England) · 45 minutes

Seismic waves as evidence for Earth's layers

Earth and rocks

CCSS NGSS.HS-ESS2-3CCSS NGSS.SEP 7England: GCSE Physics: Waves (seismic waves, Physics only)

Objective and success criteria

Students will: Seismic waves as evidence for Earth's layers.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: The structure of the Earth; Transverse and longitudinal waves

Leads to: the next skill in this area.

Materials: Rock samples, Hand lenses, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (The structure of the Earth; Transverse and longitudinal waves). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Is this a transverse or a longitudinal wave: a slinky pushed and pulled along its length? (transverse / longitudinal) → longitudinalPrompt: Compare the direction of vibration with the direction the wave travels.
  2. What is the Earth's core mainly made of? (rock and soil / gold / iron and nickel / water) → iron and nickelPrompt: It is metallic and very dense.
  3. Is this a transverse or a longitudinal wave: sound? (transverse / longitudinal) → longitudinalPrompt: Compare the direction of vibration with the direction the wave travels.

Hook · 5 min

  • Pass round different rocks and ask how each one might have formed.
  • Share the objective: Seismic waves as evidence for Earth's layers. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: At a seismometer, the S waves arrive 15 s after the P waves. Assume P waves travel at 8 km/s and S waves at 4 km/s. How far away was the earthquake, in km?
  • Step 1: 1/4 − 1/8 = 1/8 s per km
  • Step 2: 15 ÷ (1/8) = 120
  • Step 3: So the answer is: 120 km
  • Answer: 120 km
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. At a seismometer, the S waves arrive 20 s after the P waves. Assume P waves travel at 8 km/s and S waves at 4 km/s. How far away was the earthquake, in km? → 160 kmPrompt: Each kilometre takes 1/4 s for S waves and 1/8 s for P waves.
  2. Why do seismic waves travel in curved paths through the mantle? (Earth's gravity bends them / Their speed changes gradually with depth, so they refract / They bounce off the surface / The Moon pulls them) → Their speed changes gradually with depth, so they refractPrompt: Waves change direction when their speed changes.

You do: independent practice · 10 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. At a seismometer, the S waves arrive 60 s after the P waves. Assume P waves travel at 8 km/s and S waves at 4 km/s. How far away was the earthquake, in km? → 480 kmPrompt: Each kilometre takes 1/4 s for S waves and 1/8 s for P waves.
  2. Why do seismic waves travel in curved paths through the mantle? (They bounce off the surface / Their speed changes gradually with depth, so they refract / Earth's gravity bends them / The Moon pulls them) → Their speed changes gradually with depth, so they refractPrompt: Waves change direction when their speed changes.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: The structure of the Earth.
  • Use concrete materials: rock samples.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-10.

Free lesson plan from eurekami.com/lesson-plan-builder

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Seismic waves as evidence for Earth's layers

Name

Date

Score/ 8

  1. Question 1

    Inside the Earth: which statement is NOT true?

    • A. Earth's inner core is solid and the outer core is liquid.
    • B. Studying seismic waves lets scientists "see" inside Earth.
    • C. The mantle is mostly liquid magma.
    • D. P waves can travel through solids and liquids.

  2. Question 2

    Why do seismic waves travel in curved paths through the mantle?

    • A. Their speed changes gradually with depth, so they refract
    • B. The Moon pulls them
    • C. Earth's gravity bends them
    • D. They bounce off the surface

  3. Question 3

    At a seismometer, the S waves arrive 45 s after the P waves. Assume P waves travel at 8 km/s and S waves at 4 km/s. How far away was the earthquake, in km?

    Answerkm

  4. Question 4

    How do seismic waves show that the inner core is solid?

    • A. P waves speed up when they enter the inner core
    • B. Waves get louder in the inner core
    • C. No waves ever reach the inner core
    • D. S waves stop at the crust

  5. Question 5

    At a seismometer, the S waves arrive 10 s after the P waves. Assume P waves travel at 8 km/s and S waves at 4 km/s. How far away was the earthquake, in km?

    Answerkm

  6. Question 6

    Which seismic waves arrive first at a seismometer?

    • A. S waves (secondary, transverse)
    • B. P waves (primary, longitudinal)
    • C. all arrive together
    • D. surface waves

  7. Question 7

    At a seismometer, the S waves arrive 30 s after the P waves. Assume P waves travel at 8 km/s and S waves at 4 km/s. How far away was the earthquake, in km?

    Answerkm

  8. Question 8

    S waves are not detected on the opposite side of Earth from an earthquake. What does this show?

    • A. S waves are faster than P waves
    • B. The crust is liquid
    • C. The core is hollow
    • D. Part of the core is liquid, because S waves cannot travel through liquids

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Answer key: Seismic waves as evidence for Earth's layers

  1. 1. C. The mantle is mostly liquid magma.

  2. 2. A. Their speed changes gradually with depth, so they refract

  3. 3. 360 km

  4. 4. A. P waves speed up when they enter the inner core

  5. 5. 80 km

  6. 6. B. P waves (primary, longitudinal)

  7. 7. 240 km

  8. 8. D. Part of the core is liquid, because S waves cannot travel through liquids