The Naked Scientists

The Naked Scientists Forum

Author Topic: Is lava magnetic? Can it record former magnetic pole shifts?  (Read 6480 times)

Offline Airthumbs

  • Hero Member
  • *****
  • Posts: 958
  • Personal Text
    • View Profile
I just watched a very interesting documentary called The Core, http://topdocumentaryfilms.com/the-core/

Within this documentary it highlights that molten lava as it cools keeps a record of the earths magnetic poles.  Does this mean that the lava is magnetic?

Following on from that, when the magnetic poles do switch would this mean that there would be a force applied to the cooled lava that is now in opposition to the magnetic poles thus causing movement of the earths crust?


[MOD EDIT - QUESTION RE-PHRASED FOR CLARITY]
« Last Edit: 24/10/2011 08:24:40 by chris »


 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
I'll take a shot, but won't be surprised if I get beaten up!

Basalt (the stuff that comes out of volcanoes) contains a bit of iron, and I think that's why it's brownish in color (if you want some, come get it - my "garden" is 80% basalt rubble.) Apparently, some basalt even has quite a bit of iron in it. I saw something recently that the basalt in some parts of Hawaii has so much iron in it, that those parts are literally rusting away.

I would assume that some of this iron retains some sort of magnetic alignment that was locked in when the basalt solidified, and that some very clever people have figured out a way to detect and measure that alignment. That would allow them to determine the direction of the Earth's magnetic field at the time when the basalt solidified.

The magnetic field produced by the basalt is probably very weak (I doubt if a normal magnetic compass would ever be able to detect it), so the opposition effect is probably negligible.
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8130
  • Thanked: 53 times
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #2 on: 24/10/2011 09:45:05 »
The magnetic field produced by the basalt is probably very weak (I doubt if a normal magnetic compass would ever be able to detect it)

Unless there is a lot of it ...
Quote
As early as the 18th century it was noticed that compass needles deviated near strongly magnetized outcrops.
http://en.wikipedia.org/wiki/Paleomagnetism#History
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #3 on: 24/10/2011 10:01:33 »
The magnetic field produced by the basalt is probably very weak (I doubt if a normal magnetic compass would ever be able to detect it)

Unless there is a lot of it ...
Quote
As early as the 18th century it was noticed that compass needles deviated near strongly magnetized outcrops.
http://en.wikipedia.org/wiki/Paleomagnetism#History

See? I told you I was going to get beaten up.
 

Offline Airthumbs

  • Hero Member
  • *****
  • Posts: 958
  • Personal Text
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #4 on: 24/10/2011 14:07:38 »
So would the crust move after the poles shift?   :P  BTW although my original question might not have been clear I already know the answer to the question it has been changed too and therefore would not have posted it..  :P
« Last Edit: 25/10/2011 00:03:38 by Airthumbs »
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #5 on: 25/10/2011 18:53:05 »
So would the crust move after the poles shift?

I think the magnetic fields can be measured in a variety of rocks including sedimentary soils and rock which can give you more of a continuous resolution than the lava which may only cover a few discrete events.

Continents do drift. 

Combining the information from several continents should help control for continental drift.
 

Offline Airthumbs

  • Hero Member
  • *****
  • Posts: 958
  • Personal Text
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #6 on: 25/10/2011 23:02:01 »
Could it be possible that if changes in the Earth's magnetic field influence the movements of the crust, you might expect more activity, such as earthquakes, volcanoes and adverse weather conditions.....  ???

What happens when you take a piece of iron that has been magnetised in one direction and apply an opposing magnetic force to it?  According to wiki Iron constitutes 6.7% of the crust.

There is evidence to suggest that magnetic poles are beginning the cycle of reversal, The South American Anomaly and the current trend of the magnetic poles accelerating each year at incremental rates.  I think the accepted theory is that this process takes thousands of years although how this conclusion is reached I don't know?

Of course the inner core of the Earth is solid iron essentially, that must be magnetic also.  Is there a connection? 





 

Offline Bass

  • Neilep Level Member
  • ******
  • Posts: 1340
  • Thanked: 5 times
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #7 on: 27/10/2011 21:21:35 »
There are magnetic minerals in crustal rocks (at least once they get below a certain "Curie" temperature).  The minerals align themselves with the magnetic poles at the time of deposition and/or cooling.  These paleomagnetic directions can be measured, which is one of the reasons that we know of magnetic reversals. 
To my knowledge, there is no correlation between magnetic reversals and changes in tectonic plate movements.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #8 on: 28/10/2011 03:12:34 »
To my knowledge, there is no correlation between magnetic reversals and changes in tectonic plate movements.

I thought the question is whether the movement of continents would contaminate the magnetic shift data. 

[Oh, I see, a second question got squeezed in.  With the shifting of the magnetic field, the very week fields from deposition of minerals also has shifted, so there wouldn't be a strong directional attraction with the continents]

 

I'm not seeing any of the continents flipping with the Pangaea theory.  However, there does appear to be some wobbling.  The wobbles would likely confound the results somewhat.  Do we truly have that much data with continent movements?

The measurements of the magnetic field covers both strength and direction.  Strength presumably is independent of the tectonic movement, unless it varies with proximity to the poles.
« Last Edit: 28/10/2011 03:25:08 by CliffordK »
 

Offline Airthumbs

  • Hero Member
  • *****
  • Posts: 958
  • Personal Text
    • View Profile
Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #9 on: 07/11/2011 20:50:14 »
The graphic you use CliffordK above is very interesting.  If you look at the graphic you can't help notice that the movement of the continents changes periodically into what seems like an opposite direction. What would cause this?  Could a change in the earths polarity cause the techtonic plates to alter the direction of movement?

Does this not seem obvious to anyone else or am I the only one who seems to find a correlation in this?

Look at the graphic and every time the continents change direction think flip and you will see what I mean....

It seems to me the reason for the lack of interest in this is because the old boys have it all tied up and woe betide anyone who messes with the apple cart.   Or they know it's going to happen and that is what the message of the ancients was by building all these earthquake resistant buildings all over the world. 

A final note on the movement of the plates, imagine how much energy is involved in changing the movement of one of the continental plates.  Something pretty massive must have occurred to make all the plates come to a stop and then reverse direction.  I am pretty self convinced on this and it's going to take a serious amount of scientific input to make me change my mind....   :o

Does anyone happen to have themselves a pyramid on very high ground I could borrow for a couple of years....  :P
 

The Naked Scientists Forum

Is lava magnetic? Can it record former magnetic pole shifts?
« Reply #9 on: 07/11/2011 20:50:14 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length