The Gauss–Matuyama Reversal was a

geologic Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

event approximately 2.58 Ma when the

Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from structure of Earth, Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from ...

underwent a

geomagnetic reversal A geomagnetic reversal is a change in the Earth's Dipole magnet, dipole magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with North Pole, geographic north and South Pole, geograp ...

from normal polarity (Gauss Chron) to reverse polarity (Matuyama Chron). The reversal is named after German physicist

Johann Carl Friedrich Gauss Johann Carl Friedrich Gauss (; ; ; 30 April 177723 February 1855) was a German mathematician, astronomer, Geodesy, geodesist, and physicist, who contributed to many fields in mathematics and science. He was director of the Göttingen Observat ...

and Japanese geophysicist

Motonori Matuyama was a Japanese geophysicist who was (in the late 1920s) 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 polarit ...

. The Gauss–Matuyama reversal is a natural phenomenon that is frequently used as a boundary between the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

epochs, marking the start of the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

period, and is often used to date sediments. The reversal is thought to have contributed to a hostile environment on Earth due to the lack of protective features of

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

s to shield life from ionizing radiation generated by the early Pleistocene

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

Biological effects

The Gauss–Matuyama reversal is marked by a minor

mass extinction An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occ ...

calcareous nannofossils Calcareous nannofossils are a class of tiny (less than 30 microns in diameter) microfossils that are similar to coccoliths deposited by the modern-day coccolithophores. The nannofossils are a convenient source of geochronological data due to ...

Discoaster ''Discoaster'' is a genus of extinct star-shaped marine algae, with calcareous exoskeletons of between 5-40 μm across that are abundant as nanofossils in tropical deep-ocean deposits of Neogene age. ''Discoaster'' belongs to the haptophyt ...

pentaradiatus'' and ''Discoaster surculus'', among others. The Earth's magnetic field is approximately four times stronger today than it was during the Gauss–Matuyama reversal. The reversal is thought to have weakened the shielding that the magnetic field provides the surface Earth, resulting in more exposure to

ionizing radiation Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...

generated by the early Pleistocene

, and leaving the Earth unshielded for ~15 ky. The propagation of charged particles is dependent in the magnetic field intensity and changes in the dipole moment found in the magnetic field. The ionospheric ionization at the poles and equator reduces the energy on cosmic rays by several orders of magnitude. During the reversal, the dipole field was reduced or entirely canceled because the virtual poles were located at low and intermediate latitudes, which would expose these regions to cosmic rays.

Methods for dating reversal

Luminescence dating Luminescence dating refers to a group of chronological dating methods of determining how long ago mineral grains were last exposed to sunlight or sufficient heating. It is useful to geologists and archaeologists who want to know when such an event ...

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

sediment are used to date the Gauss–Matuyama reversal. This method is a form of geochronology that measures the amount of photons released from a material after being stimulated. This method primarily observes the movement of U, Th, Rb and K as ionizing radiation. The product of stimulating these elements is a reliable date on the sediment.

References

{{DEFAULTSORT:Gauss-Matuyama reversal

Biological effects

Methods for dating reversal

See also

References