Has anyone seen the film where polar reversal within the time of humans is proved through an ancient campfire?

Question

This was something I saw twenty years ago in a geology class in college. I know all about the evidence shown through zebra striping in the basalt on the ocean floor, but am interested in any information about this particular experiment. They dug up an ancient campfire that supposedly had heated the rock so much that it allowed the ions to realligne.

Answer 1

There is now a whole subspecialty of paleomagnetism and archaeology called archaeomagnetism that utilizes the phenomenon you are talking about in the study of archaeological sites. Kilns and hearths have been especially useful in this field, as they were regularly heated to fairly high temperatures, which did allow for realignment of microscopic magnetic particles such as hematite and magnetite with lines of flux in the magnetic field of the earth. By recording the orientations of the particles in old kilns etc, which have been accurately dated by other methods, dating scales of magnetic orientations have been developed.(last 2 sentences paraphrased from last url on list bleow, which has a nice virtual tour of the application an archaeomagnetism study at an archaeological site.
I'm directing you to a few informative sites:
http://www.u.arizona.edu/~slengyel/amag2_new-sw_002.htm
http://www.mnsu.edu/emuseum/archaeology/dating/dat_mag.html
http://www.bradford.ac.uk/acad/archsci/depart/resgrp/archmag/menu.php?2
http://www.meteo.be/CPG/aarch.net/onlytxt/no.frame.html
http://farahsouth.cgu.edu/tour/archaeomagnetism/

Answer 2

I am not sure the example you're thinking of was necessarily a campfire. I recall an example in my geophysics class of a magnetometer survey done over the site of a former, burned down fort in Canada. The fire had burned so hot that it had realigned the magnetic material in the post holes and they were anomalous relative to the background rock that the posts were located in.

The example was fascinating and provided the exact location of the supports of the fort.

Hope that helps!

Answer 3

when a mineral is heated to the melting point, the ions will realign to the gravitational field of the earth, as time moves on, the gravitational field will shift so that any local change in the pattern is easily seen by analysis. So your campfire would have done this in a small area and could then be proved to be man-made

Answer 4

Nope but it looks like a very interesting movie.