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An extremely brief reversal of the geomagnetic field, climate variability and a super volcano
http://www.alphagalileo.org/ViewItem.aspx?ItemId=124996&CultureCode=en[font face=Serif][font size=5]An extremely brief reversal of the geomagnetic field, climate variability and a super volcano[/font]
16 October 2012 Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
[font size=3]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 radiation exposure.
This is documented by peaks of radioactive beryllium ([font size=1]10[/font]Be) in ice cores from this time, recovered from the Greenland ice sheet. [font size=1]10[/font]Be as well as radioactive carbon ([font size=1]14[/font]C) is caused by the collision of high-energy protons from space with atoms of the atmosphere.
…
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.
…[/font][/font]
http://dx.doi.org/10.1016/j.epsl.2012.06.05016 October 2012 Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
[font size=3]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 radiation exposure.
This is documented by peaks of radioactive beryllium ([font size=1]10[/font]Be) in ice cores from this time, recovered from the Greenland ice sheet. [font size=1]10[/font]Be as well as radioactive carbon ([font size=1]14[/font]C) is caused by the collision of high-energy protons from space with atoms of the atmosphere.
…
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.
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http://wdc.kugi.kyoto-u.ac.jp/poles/polesexp.html
Since 1970 its rate of motion has accelerated from 9 km/year to approximately 41 km/year, or 1.3 mm/sec (2001–2003 average
http://en.wikipedia.org/wiki/North_Magnetic_Pole
http://news.nationalgeographic.com/news/2009/12/091224-north-pole-magnetic-russia-earth-core/
Magnetic field appears to be weakening:
http://news.nationalgeographic.com/news/2006/05/magnetic-field-1.html
http://www.ngdc.noaa.gov/geomag/GeomagneticPoles.shtml
http://www.geomag.bgs.ac.uk/education/earthmag.html#_Toc2075558
[font face=Serif][font size=4]3.4 Geomagnetic jerks[/font]
[font size=3]The rate of change of declination at Lerwick, Eskdalemuir and Greenwich-Abinger-Hartland observatory series in the UK is shown in Figure 7. It can be seen from this plot that there have been a number of changes in the general trend of secular variation in the past, in particular at about 1925, 1969, 1978 and 1992. These sudden changes are known as jerks or impulses and, at the present time, are not well understood and are certainly not predictable. Some researchers have found evidence for a correlation with length-of-day changes.
[/font][/font]
[font size=3]The rate of change of declination at Lerwick, Eskdalemuir and Greenwich-Abinger-Hartland observatory series in the UK is shown in Figure 7. It can be seen from this plot that there have been a number of changes in the general trend of secular variation in the past, in particular at about 1925, 1969, 1978 and 1992. These sudden changes are known as jerks or impulses and, at the present time, are not well understood and are certainly not predictable. Some researchers have found evidence for a correlation with length-of-day changes.
[font size=1] Figure 7: Rate of change of declination at Greenwich (GRW), Abinger (ABN), Hartland (HAD), Eskdalemuir (ESK) and Lerwick (LER) observatories 1900-2010[/font]
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