Re: What will happen if the earh's poles switch places?

We think this happens regularly, but not often, at least not since 
recorded history began.  Our best guess is it last happened about 11,000 
years ago, before written records and of course before magnetic media like 
computer disks.

See 

http://www.madsci.org/posts/archives/nov98/912372013.Es.r.html for 
more about the earth's magnetic field, and why it may change sometimes.

Since nobody has never recorded a magnetic pole switch, we dont know for 
sure how it happens.  How it affects our everyday lives depends greatly on 
how fast it happens.  The sun changes magnetic poles every 11 years, it 
happens slowly and we can watch the sunspots multiply and die away during 
each cycle.  

If this happened slowly on earth we might not notice much except our 
magnetic compasses would drift away from true north.  We already correct 
for "magnetic variation" or the difference between magnetic north (the 
magnetic pole) and true north (the axis of rotation).  And we watch this 
difference change year by year.

We are not sure if very sudden changes ever happen.  If a large difference 
in magnetic poles happened very quickly, say, in a few hours or days it 
could mean big trouble for electric power grids and radio communications.  
The sun often ejects bubbles of energy that change the magnetic field of the
earth, sometimes enough to cause troubles.  We dont see "storms" like tornadoes, 
but "magnetic storms" my be undetected by our human senses but still cause 
big problems with electricity and communications.

One problem is that big, slow electrical currents flow inside the earth.  
Our power grids use the earth as a "GROUND" so these currents get into the 
power grid and cause transformer cores to saturate, and circuit breakers 
to trip off.  Sometimes big electric power companies hire forecasters to 
help them wait for a calm between the storms to put new power plants on 
line.  These storms are a less than 1% of the total earth field, so you 
can imagine the power companies would have a trouble delivering their 
power if the whole earth field changed very suddenly.  So far we think the 
changes are slow enough to handle, but we could get a big surprise one 
day !

If a change happened suddenly enough, yes, there could be earthquakes.

The study of these phenomena and attempts to predict future changes are 
very important.