Geomagnetic reversal dating

01-May-2017 10:03

Apparent motions of the north geomagnetic pole recorded in sequences of lava flows during several reversals.Each colour corresponds to a distinct reversal record.Also shown in the center of the planet is the solid inner core (red) surrounded by the conducting liquid outer core (orange).Credit: Valet and Fournier, 2016, doi:10.1002/2015RG000506 Earth’s natural magnetic field is generated by complex motions of molten iron alloys in the outer core of the planet, at depths in excess of 2,900 km, and varies on time scales ranging from milliseconds to millions of years.We learned also that field geometry during the transition is much more complex with several poles wandering at the surface of the earth and can thus be described as a multipolar field.However it is very difficult to obtain a good description of the field geometry (quadrupolar, octopolar etc…) and to describe its time-evolution.A recent article published in by Jean-Pierre Valet and Alexandre Fournier of Institut de Physique du Globe de Paris provides a mature reflection on the challenges faced in such research, with a critical review of the main reversal features derived from paleomagnetic records and analyses of some of these features in light of numerical simulations.

In fact, there is no perfect magnetic recorder, most sediments are characterized by low temporal resolution and volcanism is sporadic in nature with lava flows irregularly distributed in time.The analysis of the database shows that the overall strength of the field, anywhere on the Earth, may be no more than a tenth of its strength now.Reversals seem to occur in several phases with a precursor and a rebound.Reversals tell us also how the earth system responds to extreme global changes of the earth’s magnetic field.What are the major unsolved or unresolved questions and where are additional data or modeling efforts needed?

In fact, there is no perfect magnetic recorder, most sediments are characterized by low temporal resolution and volcanism is sporadic in nature with lava flows irregularly distributed in time.

The analysis of the database shows that the overall strength of the field, anywhere on the Earth, may be no more than a tenth of its strength now.

Reversals seem to occur in several phases with a precursor and a rebound.

Reversals tell us also how the earth system responds to extreme global changes of the earth’s magnetic field.

What are the major unsolved or unresolved questions and where are additional data or modeling efforts needed?

AGU asked the authors of the article to highlight the important results that have emerged from their research and some of the important questions that remain. What recent advances in particular are leading to a new understanding or synthesis?