Most of Earth's earthquakes and volcanic eruptions occur at the boundaries of the tectonic plates. This dataset shows all earthquakes of magnitude 5.0 or greater from 1960 through 2010. The earthquakes are illustrated with a large white dot at the time of the event. The size of the dot is proportional to the magnitude of the earthquake. A musical tone is generated for the larger events. The larger the earthquake, the lower the tone. The white dots eventually turn gray and slowly shrink to single-pixel dots.
Likewise, volcanic eruptions are shown as red triangles as they occur. Like earthquakes, volcanic eruptions are assigned a magnitude called the Volcanic Explosivity Index (VEI) based on the volume of material ejected during the eruption. These magnitudes run from one to eight, with none greater than five in this dataset. A given eruption might go through several changes of size during the eruption. The sound generated when a volcano erupts is made by percussion instruments, with the largest—a magnitude five-accompanied by the sound of a crashing cymbal. For example, the eruption of Mount Pinatubo in the Philippines in 1991 is accompanied by the sound of a crashing cymbal. Unlike earthquakes that last (at most) a few minutes, an eruption can go on for years. As long as it is erupting, it is shown as a red triangle. When the eruption is done, the triangle disappears. Dates are displayed along with the number of earthquakes and volcanic eruptions that have occurred since 1960.