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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: ripples on a pond? (transverse / longitudinal) → transversePrompt: Compare the direction of vibration with the direction the wave travels.
  2. How do scientists know about the inside of the Earth? (By looking at the Moon / By visiting the core / By drilling to the centre / By studying how earthquake waves travel through it) → By studying how earthquake waves travel through itPrompt: The deepest hole ever drilled is only about 12 km deep.
  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 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? → 120 kmPrompt: Each kilometre takes 1/4 s for S waves and 1/8 s for P waves.
  2. How do seismic waves show that the inner core is solid? (P waves speed up when they enter the inner core / Waves get louder in the inner core / No waves ever reach the inner core / S waves stop at the crust) → P waves speed up when they enter the inner corePrompt: Waves travel faster through solids than liquids.

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. How do seismic waves show that the inner core is solid? (S waves stop at the crust / Waves get louder in the inner core / No waves ever reach the inner core / P waves speed up when they enter the inner core) → P waves speed up when they enter the inner corePrompt: Waves travel faster through solids than liquids.
  2. Inside the Earth: which statement is NOT true? (Studying seismic waves lets scientists "see" inside Earth. / S waves are longitudinal. / Earth's inner core is solid and the outer core is liquid. / P waves can travel through solids and liquids.) → S waves are longitudinal.Prompt: How deep is the deepest hole ever drilled?

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

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

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

  2. Question 2

    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

  3. Question 3

    Inside the Earth: which statement is NOT true?

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

  4. Question 4

    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?

    Answerkm

  5. Question 5

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

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

  6. Question 6

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

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

  7. Question 7

    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?

    Answerkm

  8. Question 8

    Which seismic waves arrive first at a seismometer?

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

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

  1. 1. C. P waves speed up when they enter the inner core

  2. 2. 360 km

  3. 3. D. S waves are longitudinal.

  4. 4. 120 km

  5. 5. B. Their speed changes gradually with depth, so they refract

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

  7. 7. 160 km

  8. 8. A. P waves (primary, longitudinal)