Though a magnetic reversal is a major planet-wide event driven by convection in Earth’s iron core, there are no documented catastrophes associated with past reversals, despite much searching in the geologic and biologic record.
Today, however, such a reversal could potentially wreak havoc with our electrical grid, generating currents that might take it down.
And since Earth’s magnetic field protects life from energetic particles from the sun and cosmic rays, both of which can cause genetic mutations, a weakening or temporary loss of the field before a permanent reversal could increase cancer rates.
Paul Renne, director of the Berkeley Geochronology Center and a University of California Berkeley professor-in-residence of Earth and planetary science is a coauthor of the study.
He said: The new finding is based on measurements of the magnetic field alignment in layers of ancient lake sediments now exposed in the Sulmona basin of the Apennine Mountains east of Rome, Italy.
The lake sediments are interbedded with ash layers erupted from the Roman volcanic province, a large area of volcanoes upwind of the former lake that includes periodically erupting volcanoes near Sabatini, Vesuvius and the Alban Hills.
What we know as the magnetic north pole was at the geographic south pole, a million years ago.
This map shows how – starting about 789,000 years ago – the north pole wandered around Antarctica for several thousand years before flipping 786,000 years ago to the orientation we know today, with the north magnetic pole in the Arctic.
Image courtesy of University of California – Berkeley Earth’s magnetic field is known to have flipped many times throughout our planet’s history.
Its dipole magnetic field, like that of a bar magnet, remains about the same intensity for thousands to millions of years, and then – for incompletely known reasons – it occasionally weakens and reverses direction.
That weakening and reversal was supposed to take on the order of several thousand years.
A new study by an international team of scientists, however, demonstrates that the last magnetic reversal – 786,000 years ago – actually happened very quickly, in less than 100 years, or roughly the span of a modern human lifetime.