• Quick retrieval from earlier learning (Plate tectonics, earthquakes and volcanoes). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. What evidence suggests the continents were once joined? (all continents are the same size / the same weather on every continent / matching fossils and rock layers on continents far apart / the oceans are salty) → matching fossils and rock layers on continents far apartPrompt: The same land reptile fossils are found in Africa and South America.
2. Two plates move apart at about 5 cm per year. How far apart will they move in 1 000 years, in kilometres? (1 km = 100 000 cm) → 0.05 kmPrompt: First find the distance in cm.
3. Plate tectonics: which statement is NOT true? (The continents have always been where they are now. / Mountains such as the Himalayas formed where plates collided. / The Earth's crust is broken into large pieces called tectonic plates. / Plates move a few centimetres each year.) → The continents have always been where they are now.Prompt: How fast do your fingernails grow? Plates move at about that speed.

• Pass round different rocks and ask how each one might have formed.
• Share the objective: Measure earthquakes and reduce their risks. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: On the magnitude scale, each whole number up means the ground shaking (wave amplitude) is 10 times larger. How many times larger is the shaking in a magnitude 8 earthquake than in a magnitude 6?
• Step 1: 8 − 6 = 2
• Step 2: 10^2 = 100
• Step 3: So the answer is: 100
• Answer: 100
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. On the magnitude scale, each whole number up means the ground shaking (wave amplitude) is 10 times larger. How many times larger is the shaking in a magnitude 5 earthquake than in a magnitude 4? → 10Prompt: How many steps up the scale is it?
2. Some countries send phone alerts seconds before strong shaking arrives. How is this possible? (Phones feel the earthquake first / They predict quakes days ahead / Sensors detect the faster, weaker first waves and send warnings before slower damaging waves arrive / Radio waves are slower than seismic waves) → Sensors detect the faster, weaker first waves and send warnings before slower damaging waves arrivePrompt: Electronic signals travel far faster than seismic waves.

• 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.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. Earthquakes: which statement is NOT true? (Undersea earthquakes can cause tsunamis. / The focus of an earthquake is always on the surface. / The point on the surface above an earthquake's origin is the epicentre. / Most earthquakes happen near plate boundaries.) → The focus of an earthquake is always on the surface.Prompt: Is the magnitude scale linear?
2. Which design feature helps a tall building survive an earthquake? (building on loose wet sand / flexible base isolators that let the ground move under the building / large glass panels with no frames / heavy concrete on the top floors) → flexible base isolators that let the ground move under the buildingPrompt: Rigid, top-heavy buildings shake apart.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-7.