Geomagnetic reversal dating
Geomagnetic reversal dating
Italian researchers measured the magnetic field directions frozen into the sediments as they accumulated at the bottom of the ancient lake.Scientists at University of California, Berkeley then used argon-argon dating, a method widely used to determine the ages of rocks, whether they’re thousands or billions of years old, to determine the age of ash layers above and below the sediment layer recording the last reversal.
Thus, climate records from the MIS 19 interglacial can be used to elucidate the mechanisms of a variety of climate changes, including testing the effect of changes in geomagnetic dipole field strength on climate through galactic cosmic ray (GCR)-induced cloud formation, as the present evidence for this effect is weak and biased toward the oceans.The light-blue areas show the estimated intervals of sea level exceeding the Osaka Bay sill (−48 ± 4 m elevation). These strengthening episodes lasted for 300‒2200 years and are synchronous between Lingtai and Xifeng, with the different shapes of variation in some episodes reflecting regional differences in sensitivity to SM because of geographic and/or climatic conditions.. For the millennial-scale climate events during the last glacial period, intensification and southward shift of the Westerlies during brief cold events in the North Atlantic have possibly caused rapid expansion of the WM, and vice versa during times of rapid warming in the North Atlantic The WM intensification occurred without anti-phase SM variation, spanning from 783‒778 ka in both Lingtai and Xifeng (Fig. The WM intensification in Xifeng was interrupted by the brief WM weakening event correlated with the somewhat broad SM intensification “x4” (Fig. In contrast, the intensification in Lingtai was least affected by the interruption that was quite short compared with that in Xifeng.The synchronous WM intensification would be caused by strengthening of the Siberian High, which is not ascribed to the winter insolation over Siberia, possibly resulting in intensification of the WM through an umbrella effect.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.Renne said: What’s incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years.
We don’t know whether the next reversal will occur as suddenly as this one did, but we also don’t know that it won’t.
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.
The danger to life would be even greater if flips were preceded by long periods of unstable magnetic behavior.
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.
High summer precipitation causes pedogenesis of loess during interglacial periods, whereas pedogenesis is weaker during glacial periods because of low summer precipitation. WM maxima without correlation with SM variations are in green. In addition to effects on global climate linked to ice volume changes, the movement of the SM front between interglacial and glacial periods in response to the regression of coastlines is a possible influential mechanism (Fig.