RenoVous

  Iceland is no stranger to volcanic and seismic activity, but recently a crack started to spread through the town of Grindavik.  It sits on the Reykjanes Peninsula, where the Fagradalsfjalls volcano is gearing up for an eruption. The cracking was caused by what's called a dike, a vertical sheet of magma within the crust.  Vincent Drouin, with the Icelandic Meteorological Office, says the dike has stopped propagating, but at the time was moving more than 2km an hour. As the magma cracks through and advances under the surface, it creates earthquakes.  Scientists had some idea of what would happen as they noticed some deformations and then a cluster of seismic activity in a repeated pattern. Researchers at the Global Seismographic Network (BORG) in Reykjavik have transformed seismic frequencies into audible pitches.  These recordings are from early November.

  Earlier this year we touched on cymatics - the science of visible sound. Then it was Chladni plates, and now it's Ruben's tube. While the plates were a study in acoustics and vibrations, the tube shows the relationship between sound waves and sound pressure. Heinrich Rubens was a German physicist born in 1865.  He worked with Max Planck on some of the ground work for quantum physics, but he is best known for his flame tube, first demonstrated in 1905. I like the trumpet. When sound is applied from one end of the tube, it changes the internal pressure. The tallest flames occur at pressure nodes, and the lowest at antinodes.  The antinodes correspond to the locations with the highest amount of compression and rarefaction.

  Cymatics is the science of visible sound, discovered by Robert Hooke in 1680.  The term wasn't coined until 1967 though, by Hans Jenny in his book Cymatics: The Study of Wave Phenomena. But it is Ernst Chladni who is credited as the father of acoustics.  He invented the technique to study the motions of vibrating plates in 1787.  Starting with a metal plate, you sprinkle some sand, and then strike a violin bow.  This would produce characteristic patterns, and Chladni was able to produce a formula that successfully predicted the patterns found on the plate. Experiments now include other means of tone making. Chladni's patterns have long been used by violin makers to test the resonance.