Tracing earthquakes: seismology in the classroom
Submitted by sis on 04 August 2006
Wave diffraction and energy transport are standard components of physics courses for 16- to 19-year-olds across Europe. Usually, students have to prove their knowledge in examinations which concentrate on the exploration of springs, Slinkies® or other classical mechanical devices.
Recent didactical research, however, stresses the importance of integrating scientific theories and models into contexts to which the students can relate. No one will have been left unaffected by the destruction caused by Hurricane Katrina in the USA or the recent earthquakes in Iran, for example.
Simplifying and explaining a concept to younger pupils is a powerful way for older students to make sure that they have thoroughly understood the topic. Developing effective demonstrations, as well as actually teaching younger pupils, fosters the multiple intelligences which proponent Howard Gardner describes as inherent to all groups of students.
The basics of seismology can be integrated into normal coursework. The experiments we describe, however, are also well suited for presenting natural sciences and their importance to a wider public - for example at school open days. And of course, the presentation skills developed by the students can be important later in life.
So much for our reasoning, as we planned a physics course with our older students. At this point, however, the creativity and enthusiasm of the students took over.
The students used web resources, newspaper reports and their textbook, but above all, they soon started to develop their own ideas of what is central and essential to seismology. They began to create model experiments, starting with coupled pendulums and culminating in an attempt to model a tsunami. Three topics proved particularly rewarding: an ancient Chinese seismograph, a simple wave machine and an investigation of earthquake-proof buildings.
Reconstructing an ancient Chinese seismograph
The main purpose of the model had been to offer a possible explanation of how the ancient Chinese seismograph worked, but the results exceeded all our expectations. Not only did even light blows to the side of the table on which the seismograph was placed cause the dragons to release their marbles, but the direction of the blow was reflected in which dragon dropped its marble. Improvements, such as using a larger mass, preventing lateral movement of the dragon heads, and constructing stiff connections between the pendulum and the dragon heads, should increase the accuracy even further.
A simple wave machine
Most wave machines are made from wood and metal spikes, but they tend to be fragile or too small for classroom display. Instead, some of our students came up with the idea of using wide bands of rubber, used in the waistbands of skirts or trousers and cheaply available. Four old bicycle wheels were donated by a local bike shop and the spokes served perfectly as arms to indicate the wave movements. The spokes were pushed through the rubber band several times and fixed with hot glue. In total, the homemade wave machine was about four metres long.
Investigating earthquake-proof buildings
Though it took some time to develop and produce the demonstrations, the motivational potential of this approach cannot be exaggerated. The students spent hours after school improving their models and testing yet further variations. All members of the course were able to contribute to the success of the project, irrespective of their abilities. This alone made the effort worthwhile, as the experience of a successful project not only helped to strengthen the group, but also enhanced their motivation and interest in other aspects of physics. And of course, the students' understanding of waves and the underlying physics improved enormously.
Physics on Stage was the forerunner of Science on Stage, an international teaching festival organised by the EIROforum. See 'Space balloons, mousetraps and earthquakes: it's Science on Stage!' and 'Science teachers take centre stage' in this issue of Science in School.
A useful web resource on wave propagation, Seismic Waves, can be downloaded free of charge here.
Tobias Kirschbaum teaches at the Städtisches Gymnasium Kamen and the Teacher Training Centre Arnsberg, Germany, while Ulrich Janzen teaches at the Franz-Stock-Gymnasium Arnsberg, Germany.