GeologyRocks

The magnetic poles do reverse every so often. That means, our compass will point south, not north sooner or later.The magnetic field is currently declining at a rate which will make it zero in around 2000 years (so no worries for a while, yet). The evidence for this reversal is recorded in the rocks, see the Plate Tectonics Tutorial 2 in our tutorial section for more info.

I doubt the reversal will have a major effect on life - there have been a few hundred recorded in the last 200Myr or so with no ill effect, but we may have trouble with radio communications etc due to an increase in solar radiation. You can find out more about this effect by looking in the the Aurora (the northern lights).

If you have any more questions, let us know!

Jon

As regards pole reversal and its effect on life, there is a recent theory that suggests pole reverals aid evolution.

There is some debate as to how long the Earth would be without a substantial magnetic field, some say a few years whereas other say the reversal would be instantaneous. During the time of weakened magnetic field, the EarthÂ’s atmosphere would be less attracted to the planet and so our protection from cosmic nasties would be reduced. ItÂ’d be like having a huge hole in the ozone layer. So I guess the bad news is that humans as we know them would be frazzled to a certain extent, even if the resulting genetic mutations may create a super-human race.

As I say this is only one school of thought, but if my memory serves me correctly there is definitely at least one study which shows a correlation between magnetic field reversals and increasing numbers of species in terrestrial creatures (as marine organisms would be less affected by solar radiation).

One thingÂ’s for sure, I wouldnÂ’t want to be here when it happens.
happy days!

I'd like to be there when it happens, just as long as my boss is as well.

Gus

interestingly enough, i was just shown a graph today in my history of the earth class that had the estimates of when pole switching has occurred in earth's history, and it's happened a lot of times they say. So it wouldn't appear to be a huge deal since it happens somewhat often (relatively speaking).

We had a discussion on magnetic reversals elsewhere - but I can't find the thread again. I said I believed it took 10,000 years, and someone else ( was it Katie or Jenny ) said 30-50 years.
I asked the BGS and their answer is copied and pasted below. We were both wrong! :oops:

Dear John

The short, and scientific consensus, answer is that a reversal probably takes about 3000-5000 years to complete. This is in contrast to the time spent in any one polarity, which, in the recent geological past has averaged about 250,000 years. It's now about 780,000 years since the last reversal.

(However, as you may understand, information on reversals comes from recording of ancient magnetic fields in rocks. A few thousand years is very short on geological scales and the time resolution of the recordings is quite coarse. So, you might find estimates of the time to reverse quoted in a wider range - 1000-10,000 years, for example.)

There's more information on reversals at our web site:

http://www.geomag.bgs.ac.uk/reversals.html

I hope this helps

Best wishes

David Kerridge
Manager, Seismology and Geomagnetism Programme

British Geological Survey
Murchison House
West Mains Road
Edinburgh
EH9 3LA

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Sent: 22 October 2005 00:31
To: *************
Subject: Ask-about-Geology question

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Ask-about-Geology question - Details:
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Name: John Willmouth

Email address: *************

Stage in education: o

Other: amateur

Question: Can you tell me how long it is thought that a magnetic reversal ( flip) actually takes please?

John

Edited your post, John, to remove email addresses - no point in giving out addresses that spammers can abuse Good to see you back too.

It probably wouldn't have been a big deal, but now it may be now. Not because we're more fagile or anything, but we use EM radiation (radio, microwaves, TV, etc) as a form of communication. The magnetic field of the Earth protects us from the worst of the solar radiation. If there's a solar flare some communications and other electrical infrastructure is damaged. One solar flare managed to knock out the power grid in a region of Canada in the 80's (At least, I think it was the 80's). Most flares have some effect on communications, even if it's a slight snow on your TV picture. The problem during the pole switch is that the Earth's magnetic field is weak, hence less solar radiation is deflacted by it, hence more trouble getting commuincations to work.

Obviously this is only a problem if we're still using EM based communications in 2000 years time - I doubt we will be

Jon

Hey Jon,
Does that mean mobile phones won't ring? Yippeeeeee! Out in Spain you rarely hear one, but as we approached Plymouth there were so many ring tones going we couldn't hear announcements! So many people wittering about nothing. Seems to me that where phones were once a tool to communicate quickly, they have now become a social event.

Sorry - reckon thgis is in the wrong place, but it does get to me!!!

John

I heard that Woodpigeons use the Earths magnetic field to navigate, I wonder where they will fly when the field is flipping?