Year 8 Science · Unit 3 · Lesson 22
Challenge Worksheet
Learning Goals
Read the graph
The bar chart below shows the approximate energy released by earthquakes of different magnitudes. Study it carefully, then answer the questions. Note: the vertical axis uses rounded scientific notation values.
Data: USGS Earthquake Hazards Program; values rounded for clarity.
(a) By how many times does the energy released increase between M5 and M6? Show your calculation using the values from the chart.
(b) How many times more energy does a magnitude 7 release compared to a magnitude 5? Use the graph values and show your working.
(c) The Richter scale is logarithmic, not linear. Explain why this matters for emergency planners and government agencies deciding how to allocate rescue resources between a magnitude 6 and a magnitude 8 earthquake.
Design a mini-experiment
A scientist wants to test: "Can a simple classroom model demonstrate how a seismograph detects different types of seismic waves (P-waves vs surface waves)?" Plan the investigation below.
| What I will change (independent variable) | |
| What I will keep the same (controlled variables, list 3) | |
| What I will measure or observe (dependent variable) | |
| Materials I would use to build the model seismograph | |
| How my model simulates P-waves (push-pull motion) | |
| How my model simulates surface waves (rolling/shaking motion) | |
| One limitation of my model compared to a real seismograph |
1. An underwater earthquake off the coast of northern Australia lifts a section of the ocean floor. What secondary hazard does this trigger, and how does the energy transfer from the earthquake to this hazard?
2. The 2011 Tōhoku earthquake off Japan measured magnitude 9.1 and caused a devastating tsunami. Using the magnitude scale, calculate approximately how many times more energy the Tōhoku earthquake released compared to the 1989 Newcastle earthquake (magnitude 5.6). Then explain what this means for the scale of emergency response required.
Wrap Up
In one sentence, what was the main idea of this lesson?