Magnetic North and History

Hello out there, has anyone got a web link or any details of how a person could determine Magnetic North co ordinates for any year in history, ?

Deirdre Kelleghan
www.irishastrosoc.org

The motions of the magnetic poles cannot be calculated or predicted be cause they are caused by unknown magma motions deep within the earth.
You can see where they are "going" at a given time but thats about it.
You can get recorded historical data of where they "were" of course.

Where can you get the data?

Deirdre Kelleghan

Admiralty charts have had this information on them since 1700,thanks to Edmund Halley,of comet fame.

I dont know of a database which gives a yearly listing, but there must be one somewhere.

There is a good tutorial on the subject at:

gsc.nrcan.gc.ca/geomag/field/magdec_e.php

This site shows Halleys original map as well.

I once saw an animation of the changes in magnetic intensity around the globe over the last century.Like watching a ghostly silhouette of the movements of churning lava deep down. Creepy.

Every several thousand years North and South flip over,leaving a magnetic record on the spreading seafloor rocks like a bar code !

On geological time scales the changes are very rapid.

According to my yacht chart twenty four Km south of Roches Point in 2004 the "secular variation" was:
" 5 degrees 55' W and Decreasing about 10' annually"

Dierdre,

I know that Met Éireann have recorded the magnetic variation for many years. I cannot find any link to the historical data but it does exist. See www.met.ie/about/valentiaobservatory/geomagnetism.asp

Data are put into the correct format for forwarding to the World Data Centres, for catering for special requests and for Magnetic Yearbook publication.

Maybe a direct contact with them might bare fruit???

Incidentally, on the "Secular Variation" page of the website I pointed you to they show,in a graph, the variation as seen from London from the early fifteen hundreds to the present day, almost five hundred years of data!:

gsc.nrcan.gc.ca/geomag/field/sec_e.php