|Manu||Date: Sunday, 06-September-2015, 10:09 PM | Message # 1|
|The planet's magnetic field is becoming less stable. In the distant past it reversed direction every 5 million years, but now it does so every 200,000 years |
By Nic Fleming
10 November 2014
The Earth's magnetic field, which protects us from potentially dangerous solar radiation, is gradually losing its stability. No need to move underground or build space colonies just yet, though: the changes are taking place over millions of years.
You might assume that compasses will always point north, but in fact the magnetic poles have swapped places many times in the Earth's history. Earth scientists have long suspected that these flips are becoming more frequent, and that the magnetic field was less prone to pole reversals in the distant past.
Now the most detailed analysis of the geological evidence to date suggests that the field really is slowly destabilising. Whereas in the distant past it reversed direction every 5 million years, it now does so every 200,000 years.
Earth's magnetic field is powered by the heart of the planet. At its centre is a solid inner core surrounded by a fluid outer core, which is hotter at the bottom. Hot iron rises within the outer core, then cools and sinks. These convection currents, combined with the rotation of the Earth, are thought to generate a "geodynamo" that powers the magnetic field.
Because of changing temperatures and fluid flows, the strength of the magnetic field varies, and the positions of the north and south magnetic poles shift.
Read more/full article/source - http://www.bbc.com/earth....s-more?