An extremely brief reversal of the geomagnetic field, climate variability and a super volcano

October 16, 2012, Helmholtz Association of German Research Centres
The polarity reversal was a global event. © Dr. habil. Norbert R. Nowaczyk / GFZ

41,000 years ago, a complete and rapid reversal of the geomagnetic field occured. Magnetic studies of the GFZ German Research Centre for Geosciences on sediment cores from the Black Sea show that during this period, during the last ice age, a compass at the Black Sea would have pointed to the south instead of north. Moreover, data obtained by the research team formed around GFZ researchers Dr. Norbert Nowaczyk and Prof. Helge Arz, together with additional data from other studies in the North Atlantic, the South Pacific and Hawaii, prove that this polarity reversal was a global event. Their results are published in the latest issue of the scientific journal Earth and Planetary Science Letters.

What is remarkable is the speed of the reversal: "The field geometry of reversed polarity, with field lines pointing into the opposite direction when compared to today's configuration, lasted for only about 440 years, and it was associated with a field strength that was only one quarter of today's field," explains Norbert Nowaczyk. "The actual polarity changes lasted only 250 years. In terms of geological time scales, that is very fast." During this period, the field was even weaker, with only 5% of today's field strength. As a consequence, the Earth nearly completely lost its protection shield against hard cosmic rays, leading to a significantly increased .

This is documented by peaks of radioactive beryllium (10Be) in ice cores from this time, recovered from the . 10Be as well as (14C) is caused by the collision of high-energy protons from space with atoms of the atmosphere.

Normal and inverse polarity of Earth. © Dr. habil. Norbert R. Nowaczyk / GFZ
The Laschamp event

The polarity reversal now found with the magnetisation of Black has already been known for 45 years. It was first discovered after the analysis of the magnetisation of several lava flows near the village Laschamp near Clermont-Ferrand in the Massif Central, which differed significantly from today's direction of the . Since then, this geomagnetic feature is known as the 'Laschamp event'. However, the data of the Massif Central represent only some point readings of the geomagnetic field during the , whereas the new data from the Black Sea give a complete image of geomagnetic field variability at a high temporal resolution.

Abrupt climate changes and a super volcano

Besides giving evidence for a geomagnetic field reversal 41,000 years ago, the geoscientists from Potsdam discovered numerous abrupt climate changes during the last ice age in the analysed cores from the Black Sea, as it was already known from the Greenland ice cores. This ultimately allowed a high precision synchronisation of the two data records from the Black Sea and Greenland. The largest volcanic eruption on the Northern hemisphere in the past 100 000 years, namely the eruption of the super volcano 39400 years ago in the area of today's Phlegraean Fields near Naples, Italy, is also documented within the studied sediments from the Black Sea. The ashes of this eruption, during which about 350 cubic kilometers of rock and lava were ejected, were distributed over the entire eastern Mediterranean and up to central Russia. These three extreme scenarios, a short and fast reversal of the Earth's magnetic field, short-term climate variability of the last ice age and the volcanic eruption in Italy, have been investigated for the first time in a single geological archive and placed in precise chronological order.

Explore further: Tracking a Jurassic reversal of the Earth's magnetic field

More information: Nowaczyk, N. R.; Arz, H. W.; Frank, U.; Kind, J.; Plessen, B. (2012): "Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments" Earth and Planetary Science Letters, 351-352, 54-69. doi:10.1016/j.epsl.2012.06.050

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3.8 / 5 (8) Oct 16, 2012
Coincidence that a super volcano erupted at about the same time as the pole reversal? I hope so because we are approaching another reversal and Yellowstone is showing signs that it's becoming active. If there is even a tiny chance of defusing Yellowstone it should be researched because an eruption there would mean the end of the USA. For one thing we are power hungry and we should start sucking every joule out of it we can. Farfetched? So was walking on the moon.
3 / 5 (1) Oct 16, 2012
From the above 'about the same time' has time difference of 1000 years (41000-39400).
3.3 / 5 (3) Oct 16, 2012
From the above 'about the same time' has time difference of 1000 years (41000-39400).

Probably within the range of error for these dates. And although I'm no geologist, I wouldn't be surprised if the events were consequentially consecutive.
5 / 5 (2) Oct 16, 2012
Coincidence that a super volcano erupted at about the same time as the pole reversal?

The story isn't very clear. They aren't saying that it happened at the same time, or that the events are related. They simply used those major events as markers in each of the different records so that they could match up years in all the different records. That allowed them to place vary narrow boundaries on the duration and sequence of events which had previously not been clear in any single record taken by itself. Some records don't show the volcano ash, while other records don't show the magnetic flipflop. Put them together using climate shifts as a link and you can say whether the volcano or the flipflop happened first.

Think of it like using the sound of the gunshot on different film recordings of the Kennedy assassination in order to match up the timing of each different camera angle.
2 / 5 (1) Oct 16, 2012
If there is even a tiny chance of defusing Yellowstone it should be researched because an eruption there would mean the end of the USA.
I'm not disagreeing, but I can't imagine any ameliorating actions we could possibly take versus perhaps the biggest example of one of the most powerful events of nature. I guess we could drill holes in it, if we could decide where to drill in a caldera so big that the edges can't be seen when one stands in the middle of it. And I think the result of that would just be some parboiled drillers.
Besides, here on the west coast things might be just fine. Just who needs the eastern half of the continent, anyway?
Curious Tim
5 / 5 (1) Oct 17, 2012
I wonder what such a dramatic reduction in field strength would be like. Obviously we survived it once( or many more), but with technology it could get crazy. Aside from that, more sunscreen?
2 / 5 (2) Oct 17, 2012
IMO the Earth did pass through dense cloud of dark matter, which accelerated the the radioactive decay of elements inside of Earth mantle. The same mechanism could be responsible for contemporary wave of global warming...

Supposed dark matter is NON-BARYONIC, decay is a process of the EM force, explain how DM can affect decay rates please.
not rated yet Oct 17, 2012
... Besides, here on the west coast things might be just fine. Just who needs the eastern half of the continent, anyway?

You have east and west backwards. Yellowstone is out west and the last time it erupted it covered the west. The problem is that if it happened it would be slow enough for everyone out there to head east. Californians would be OK but who would want Texans around?
Doc Skinner
not rated yet Oct 18, 2012
Would a worthwhile event to add to this time period be the emergence of Cro-Magnon, and a little further on those fabulous cave paintings circa 35-39ky? These, a pole reversal and 5% magnetic field strength are rather strange anomalies indeed. I also realize that the resulting increase in cosmic radiation is a favorite cause for mutations and accelerated evolution. Where things get a little wonky would be the implied carbon-14 re-up that definitely could skew commonly used dating technique. On a much larger scale it would be interesting to sync solar system events to this timeline - sunspots, comet activity, local and galactic nova activity. I also note these events occur in a cold environment. We are in a warm one, albeit exacerbated by human activity. Mitigating (super) volcanic activity is impractical even if it were possible. It's better to get the heck away. Preventing or lessening a Yellowstone event will require applications of currently unacceptable theories...

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