Year 8 Science · Unit 3 · Lesson 20
Apply Worksheet
Learning Goals
Order the steps
Number the events from 1 to 6 to show the correct order. Event 1 = what happens first.
| Order | Event |
|---|---|
| Seismographs on the opposite side of Earth detect P-waves arriving, but no S-waves, a "shadow zone" is identified. | |
| Scientists infer that the outer core must be liquid, because S-waves cannot travel through liquid material. | |
| A major earthquake occurs, releasing energy from a focus deep underground. | |
| S-waves (shear waves) are also generated and travel outward through solid rock. | |
| P-waves (compression waves) travel outward and pass through every layer of Earth, including the outer core. | |
| S-waves reach the outer core and are blocked, they cannot continue because liquid does not transmit shear waves. |
Real-world context
Imagine you could drill a hole from Sydney straight down through the centre of Earth and out the other side. The Kola Superdeep Borehole in Russia, the deepest ever drilled, reached only 12.3 km before heat and pressure made drilling impossible. Earth's radius is 6,371 km. Describe your imaginary journey through each layer.
(a) Crust, What material would you encounter, and what is the approximate depth of this layer? What challenge would drilling present here?
(b) Mantle, Describe the material, approximate temperature range, and the main challenge of drilling through this layer.
(c) Outer core, What state is it in, what is it made of, and why would a drill be destroyed almost immediately?
(d) Inner core, What is surprising about its state of matter? Explain why it behaves this way despite its temperature of ~5000°C.
1. A seismograph station records P-waves but no S-waves from an earthquake. What does this tell scientists about what lies between the earthquake's source and that station?
2. How are the oceanic and continental crust different? Include at least two differences in your answer.
Wrap Up
In one sentence, what was the main idea of this lesson?