Why Does The Earth Hum?

Posted Aug 11, 2009

The Earth hums.  Most people cannot hear it themselves, but in some parts of the world, it is noticeable.  Scientists became curious and started investigating.  Now the solution has been found about why the Earth hums.

The humming was first noticed in 1998 and scientists have learned that it is not caused by earthquakes or atmospheric turbulence.  The humming is caused by ocean waves that collide with the seafloor.  The humming primarily takes place along the Pacific coast of North America.  Some of the humming is also contributed by the ocean along the west coast of Europe.

Supposedly when two waves travelling in opposite directions collide with each other, they send a pressure wave with energy to the bottom of the ocean.  When the waves hit the sea floor, a constant vibration is generated with a frequency of 10 millihertz.  And then when you extrapolate this happening constantly with many waves, it causes a louder and more noticeable humming noise.

Scientists can detect the humming using seismometers.  An observatory called the USArray EarthScope discovered where the humming originated.  The data for the humming study was published this past Thursday in the Geophysical Research Letters.  The data for the study was gathered between November 2006 and June 2007.

[via Wired]