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Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo.
Tektites are gravel-sized bodies composed of black, green, brown or grey natural glass formed from terrestrial debris ejected during meteorite impacts. The term was coined by Austrian geologist Franz Eduard Suess (1867–1941), son of Eduard Suess. They generally range in size from millimetres to centimetres. Millimetre-scale tektites are known as microtektites.
Polar drift is a geological phenomenon caused by variations in the flow of molten iron in Earth's outer core, resulting in changes in the orientation of Earth's magnetic field, and hence the position of the magnetic north- and south poles.
Lake El'gygytgyn is a lake in Anadyrsky District, Chukotka Autonomous Okrug in northeast Siberia, about 150 km (93 mi) southeast of Chaunskaya Bay.
Zhamanshin is a meteorite crater in Kazakhstan. It is 14 kilometres (8.7 mi) in diameter and the age is estimated to be 900,000 ± 100,000 years (Pleistocene). The crater is exposed at the surface.
Paleomagnetism is the study of magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called paleomagnetists.
The Brunhes–Matuyama reversal, named after Bernard Brunhes and Motonori Matuyama, was a geologic event, approximately 781,000 years ago, when the Earth's magnetic field last underwent reversal. Estimations vary as to the abruptness of the reversal. A 2004 paper estimated that it took over several thousand years; a 2010 paper estimated that it occurred more quickly, perhaps within a human lifetime; a 2019 paper estimated that the reversal lasted 22,000 years.
Allan Verne Cox was an American geophysicist. His work on dating geomagnetic reversals, with Richard Doell and Brent Dalrymple, made a major contribution to the theory of plate tectonics. Allan Cox won numerous awards, including the prestigious Vetlesen Prize, and was the president of the American Geophysical Union. He was the author of over a hundred scientific papers, and the author or editor of two books on plate tectonics. On January 27, 1987, Cox died in an apparent suicide.
A geomagnetic excursion, like a geomagnetic reversal, is a significant change in the Earth's magnetic field. Unlike reversals, an excursion is not a "permanent" re-orientation of the large-scale field, but rather represents a dramatic, typically a (geologically) short-lived change in field intensity, with a variation in pole orientation of up to 45° from the previous position.
A geomagnetic reversal is a change in a planet'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 predominant direction of the field was the same as the present direction, and reverse polarity, in which it was the opposite. These periods are called chrons.
Lake Mungo is a dry lake located in New South Wales, Australia. It is about 760 km due west of Sydney and 90 km north-east of Mildura. The lake is the central feature of Mungo National Park, and is one of seventeen lakes in the World Heritage listed Willandra Lakes Region. Many important archaeological findings have been made at the lake, most significantly the discovery of the remains of Mungo Man, the oldest human remains found in Australia, Mungo Woman, the oldest human remains in the world to be ritually cremated and as the location of the Lake Mungo geomagnetic excursion, the first convincing evidence that Geomagnetic excursions are a geomagnetic phenomenon rather than sedimentological.
The Australasian strewnfield is the youngest and largest of the tektite strewnfields, with recent estimates suggesting it might cover 10%–30% of the Earth's surface. Research indicates that the impact forming the tektites occurred around 788,000 years ago, most likely in Southeast Asia.
The Gauss–Matuyama Reversal was a geologic event approximately 2.58 Ma when the Earth's magnetic field underwent a geomagnetic reversal from normal polarity to reverse polarity. The reversal is named after German physicist Johann Carl Friedrich Gauss and Japanese geophysicist Motonori Matuyama.
Motonori Matuyama was a Japanese geophysicist who was the first to provide systematic evidence that the Earth's magnetic field had been reversed in the early Pleistocene and to suggest that long periods existed in the past in which the polarity was reversed. He remarked that the Earth's field had later changed to the present polarity. The era of reversed polarity preceding the current Brunhes Chron of normal polarity is now called the Matuyama Reversed Chron; and the transition between them is called the Brunhes–Matuyama or Matuyama-Brunhes reversal.
The Vine–Matthews–Morley hypothesis, also known as the Morley–Vine–Matthews hypothesis, was the first key scientific test of the seafloor spreading theory of continental drift and plate tectonics. Its key impact was that it allowed the rates of plate motions at mid-ocean ridges to be computed. It states that the Earth's oceanic crust acts as a recorder of reversals in the geomagnetic field direction as seafloor spreading takes place.
Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their characteristic remanent magnetization (ChRM), that is, the polarity of Earth's magnetic field at the time a stratum was deposited. This is possible because volcanic flows acquire a thermoremanent magnetization and sediments acquire a depositional remanent magnetization, both of which reflect the direction of the Earth's field at the time of formation. This technique is typically used to date sequences that generally lack fossils or interbedded igneous rock. It is particularly useful in high-resolution correlation of deep marine stratigraphy where it allowed the validation of the Vine–Matthews–Morley hypothesis related to the theory of plate tectonics.
The Laschamp or Laschamps event was a geomagnetic excursion. It occurred between 42,200 and 41,500 years ago, during the end of the Last Glacial Period. It was discovered from geomagnetic anomalies found in the Laschamps lava flows in Clermont-Ferrand, France in the 1960s.
Magnetic field reversal may refer to:
Solar phenomena are natural phenomena which occur within the atmosphere of the Sun. These phenomena take many forms, including solar wind, radio wave flux, solar flares, coronal mass ejections, coronal heating and sunspots.
References
- ↑ Herrero-Bervera, Emilio, and S. Keith Runcorn. "Transition Fields during the Geomagnetic Reversals and Their Geodynamic Significance." Philosophical Transactions: Mathematical, Physical, and Engineering Sciences, Vol. 355 No. 1730 (September 15, 1997), pp. 1713–42.
- ↑ Glass, B. P., Swincki, M. B., & Zwart, P. A. (1979). "Australasian, Ivory Coast and North American tektite strewnfields - Size, mass and correlation with geomagnetic reversals and other earth events" Lunar and Planetary Science Conference, 10th, Houston, Tex., March 19–23, 1979, p. 2535-2545.
- ↑ Courtillot, Vincent. Evolutionary Catastrophes: The Science of Mass Extinction. Cambridge, Cambridge University Press, 1999; p. 104.
- ↑ Schneider, D.A. and Kent, D.V., 1990. Ivory Coast microtektites and geomagnetic reversals. Geophysical Research Letters, 17(2), pp.163-166.
