Brunhes-Matuyama reversal
Encyclopedia
The Brunhes–Matuyama reversal, named after Bernard Brunhes
and Motonori Matuyama
, was a geologic
event, approximately 780,000 years ago, when the Earth's magnetic field
last underwent reversal
. The reversal may have occurred slowly over several thousand years, or more quickly; opinions vary. The apparent duration at any particular location varied from 1,200 to 10,000 years depending on geomagnetic latitude and local effects of non-dipole components of the Earth's field during the transition. The event is useful in dating ocean sediment cores and subaerially erupted volcanics.
Bernard Brunhes (physicist)
Bernard Brunhes was a French geophysicist known for his pioneering work in paleomagnetism, in particular, his 1906 discovery of geomagnetic reversal. The Brunhes–Matuyama reversal is named for him....
and Motonori Matuyama
Motonori Matuyama
was a Japanese geophysicist who was the first to surmise that the Earth's magnetic field had undergone reversals in the past. The era of reversed polarity preceding the current Brunhes era of normal polarity is called the Matuyama reversed chron and the boundary between them is called the...
, was a geologic
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
event, approximately 780,000 years ago, when the Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
last underwent reversal
Geomagnetic reversal
A geomagnetic reversal is a change in the Earth's magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth's field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse...
. The reversal may have occurred slowly over several thousand years, or more quickly; opinions vary. The apparent duration at any particular location varied from 1,200 to 10,000 years depending on geomagnetic latitude and local effects of non-dipole components of the Earth's field during the transition. The event is useful in dating ocean sediment cores and subaerially erupted volcanics.
Further reading
- Behrendt, J.C., Finn, C., Morse, L., Blankenship, D.D. "One hundred negative magnetic anomalies over the West Antarctic Ice Sheet (WAIS), in particular Mt. Resnik, a subaerially erupted volcanic peak, indicate eruption through at least one field reversal" University of Colorado, U.S. Geological Survey, University of Texas. (U.S. Geological Survey and The National Academies); USGS OF-2007-1047, Extended Abstract 030. 2007.