Magnetic studies performed on sediment cores from the Black Sea by theGFZ German Research Centre for Geosciencesshow that Earth experience a speedy ( over 440 class period ) and perfect change of mind of the geomagnetic field 41,000 years ago during the last frosting age . Geomagnetic reversal lead in the interchanging of the positions of magnetic magnetic north and magnetic south . As this was a brief and unsustained terminal reversion , it is jazz as a geomagnetic digression and not a full reversal . The evidence for this brief perch reversal is further bolstered by data point obtained from extra studies perform in the North Atlantic , the South Pacific and Hawaii ; together this shows the polarity reversal was a world event . The deposit cores also provide further grounds for the last ice age and a supervolcano extravasation .

world has had several pole reversals in the last 20 million years , with a complete pole flip-flop happen about every 200,000 to 300,000 years . The last major pole reversal happen close to 780,000 class ago and is known as the Brunhes – Matuyama reversal . A turnabout does not happen instantly , and typically takes between 1,000 and 10,000 years . The Brunhes – Matuyama reversal cause no drastic changes in plant or fauna life as allow by evidence from the fogey book . By attend at oxygen isotope ratios in abstruse ocean sediment core , no changes in glacial activity were happen for this catamenia either .

The field geometry of reversed polarity for the geomagnetic excursion of 41,000 years ago lasted about 440 years and the field persuasiveness was only about 25 % of today ’s field . The actual mutual opposition lasted only 250 years , which is signally short . During this 250 - year geological period , the magnetised field was only at 5 % of today ’s bailiwick intensity . This importantly lowered Earth ’s aegis against hard cosmic rays , which in routine led to an increased exposure to radiation therapy . grounds for this is prove by top of radioactive beryllium ( 10Be ) in shabu cores recovered from the Greenland ice weather sheet .

10Be is formed in Earth ’s atmosphere through the hit of cosmic beam with atoms . 10Be has a half - sprightliness of 1.36 million year before decaying to 10Boron . period of high solar activity lessen the state of flux of cosmic rays that hit Earth , so the production of 10Be is inversely relative to solar activity and increased solar wind .

This geomagnetic excursion has been fuck about for 45 year , after the depth psychology of the magnetisation of several lava flows near the village Laschamp near Clermont - Ferrand in the Massif Central . The magnetization of these lava flow differed importantly from the direction of the geomagnetic field today . This feature has since been known as the ' Laschamp event ' . Before the in vogue work by the GFZ , the Laschamp upshot was show only by point version of the geomagnetic field during the last sparkler age . This unexampled enquiry give a more complete panorama .

The sediment cores from the Black Sea not only show the geomagnetic excursion of 41,000 years ago , they also indicate several sharp clime changes during the last ice years . These climate changes were already known from the Greenland ice cores , but now there is a mellow synchronisation between the data criminal record from the Black Sea and Greenland . The deposit CORE also document the big volcanic eruption in the northerly hemisphere of the last 100,000 year : the blast 39,400 years ago of a ace vent near Naples , Italy , experience as the Campanian Ignimbrite super - eruption . About 350 cubic kilometres of rock and roll and lava were oust from the volcano and spread over the easterly Mediterranean and as far as central Russia .

Interestingly , one of theNeanderthal extinction hypothesesinvolves clime variety . During the last methamphetamine hydrochloride geezerhood , Europe changed into a semi - arid desert and it is ruminate that Neanderthals did not conform their hunting techniques to this new environment . Volcanic eruptions , such as the super eruption near Naples 39,400 geezerhood ago , also may have contributed to a reducing in food supply .

Excavations at Mezmaiskaya Cave in the Caucasus Mountains of southerly Russia showed there was also a reduction in plant pollen at the time . Two distinct layers of volcanic ash tree were honor in the cave , which coincided with large - scale volcanic upshot that pass around 40,000 years ago . The first volcanic result is the Campanian Ignimbrite superintendent - eruption . The second volcanic stratum concur with the goal of Neanderthal presence at Mezmaiskaya and coincides with a smaller eruption thought to have occurred around the same time in the Caucasus Mountains .

NASA has more information on terminal reversalshere .