Tuesday, November 29, 2005

Sand Dunes & Icebergs: Various Artists

Before I begin, I feel that I should apologise for the sparseness of my posting lately. The problem is that I am currently rushed of my feet trying to finish part of my MSc that cannot be done at home. Hopefully it will all be done and dusted by the weekend so I can prepare the next instalment of real men of genius for you to enjoy. Anyway until next time, here is a little something about singing sand dunes and icebergs.

Since the golden age of exploration, there have been many reports of mysterious ‘songs’ being emitted from certain sand dunes in various parts of the world. As sand avalanches down the side of the huge dunes they emit a vast array of noises ranging from loud booms to drum rolls, apparently some are even quite tuneful. This mysterious desert soundtrack can be as loud as low flying aircraft, and can last for up to 15 minutes at a time.

French scientist, Stéphane Douady found that the sands responsible for producing the sounds are smoothly coated with silicon, iron and manganese. Whilst he is unsure exactly why the coated grains produce the noise, he has found that grains with coating worn away do not produce any noise at all- explaining why only some dunes can ‘sing’. Douady’s also correctly predicted the notes of ‘singing’ dunes from all over the world, by measuring the grain size.

Scientists studying earthquakes in Antarctica recently discovered another natural ‘singing’ talent- Icebergs. Whilst monitoring seismic activity in the region, they noticed a pattern of vibrations that instead of tailing off (as those made by earthquakes do), they oscillated regularly giving a comb shaped pattern of regular peaks. Patterns like this had been seen previously from volcano tremors, but this offered no explanation as to why the signals source appeared to be moving around Antarctica. Whilst these sounds are not audible to humans, they can be heard if they are sped up- the sounds vary greatly from buzzing like bees, to a more melodic sound reminiscent of string orchestras.

In 2000, they managed to pinpoint the source of two 16-hour quakes to a 400 metre tall iceberg. It is believed the tremors are caused by water rushing through crevasses inside the icebergs at high pressure, causing the ice to vibrate at regular intervals. This occurs when icebergs bang against the seabed and slow down.

If you’re curious about what these iceberg ‘songs’ are like here’s the link:
http://www.newscientist.com/data/images/ns/av/dn8374.au

Whilst these geographic songbirds are unlikely to make it the top of the pop music charts, you never know they may someday make it onto CDs sold in new age gift shops- alongside Whale songs and sounds of the womb.

Take it easy

DWB

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