How strong is the memory of the geomagnetic field? A critical appraisal of reversal asymmetry in precambrian rocks of Scotland

Lead Research Organisation: University of Liverpool
Department Name: Earth Surface Dynamics

Abstract

The Earth's magnetic field reverses its polarity such that after a reversal magnetic compasses point in the opposite geographical direction. This has occurred repeatedly throughout geological time. In general, reversals of the field are anti-parallel and the directions of magnetisation before and after a reversal lie at 180 degrees to each other. However, there are now several cases where the directions of magnetisation recorded in rocks indicate that a series of reversal may not have been anti-parallel. These observations might be the products of several magnetisation events and in these circumstances the directions reflect different parts of the geological history of the sampling site and not unusual behaviour of the field. This project is designed to test if ancient magnetisations have recorded such unusual behaviour. As with many other natural systems atypical behaviour (e.g. illness) can be as informative as the normal state. Thus, these results may lead to a greater understanding of how the Earth's field behaves and has evolved.

Publications


10 25 50
 
Description There is very strong evidence that over the last 2000 million years the Earth's magnetic field has frequently reversed it's polarity such that the north magnetic pole switched geographical position with the southern magnetic pole. This research has shown that over an interval of say 30 million years (approximately 1000 million years ago) the Earth's magnetic field reversed its polarity several tens of times but instead of the poles occupying positions 180 degrees apart they lay at 140 degrees apart; a phenomenon described as an asymmetrical reversal. Asymmetrical reversals are not restricted to this time interval and they provide information on the behaviour of the magnetic from which the source and stability of the Earth's magnetic field may be understood. During asymmetric reversals the Earth's magnetic field is acting an unusual or atypical way and this can provide information on its origins just as some diseases and occupational illnesses allowed physicians in the 19th century to determine the functions of many organs.
Exploitation Route The data an observations can be used to test and constrain mathematical models of the behaviour of the Earth's magnetic field
Sectors Education
 
Description The findings have been reported at several discipline related research meetings. The Search for Latent Components of Magnetisation in Late Precambrian Sediments of Northwest Scotland. Abstract, Magnetic Relaxation Research Meeting, Liverpool, 2012. Joint paper with Professor R.T. Holme, University of Liverpool. Are All Reversals Symmetric? The Search for Latent Components of Magnetisation in Late Precambrian (Torridonian) Sediments of Northwest Scotland. Abstract, European Geoscience Union, Vienna, 2012. Joint paper with Professor R.T. Holme, University of Liverpool Are All Reversals Symmetric? Non-anti-parallel reversals from the late Precambrian. Abstract, Symposium on the Study of the Earth's Deep Interior, Leeds 2012. Joint paper with Professor R.T. Holme, University of Liverpool. As defined in the notes this research has had no impact beyond academia though, it has been included in Engagement Activities
First Year Of Impact 2012
Sector Education
 
Description Liverpool Geological Society Monthly Meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Lively and thoughtful discussions followed

None
Year(s) Of Engagement Activity 2014
 
Description Scibar talk (Knutsford) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Lively and thoughtful discussions

None
Year(s) Of Engagement Activity 2011
 
Description U3A Group of the Royal Astronomical Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Lively and thoughtful discussions followed

None
Year(s) Of Engagement Activity 2011