The Laschamp or Laschamps event, also termed the Adams event, was a

geomagnetic excursion A geomagnetic excursion, like a ''geomagnetic reversal'', is a significant change in the Earth's magnetic field. Unlike ''reversals'', an excursion is not a long-term re-orientation of the large-scale field, but rather represents a dramatic, typica ...

(a short reversal of the Earth's magnetic field). It occurred between 42,200 and 41,500 years ago, during the Last Glacial Period. It was discovered from geomagnetic anomalies found in the Laschamps and Olby lava flows near

Clermont-Ferrand Clermont-Ferrand (, , ; or simply ; ) is a city and Communes of France, commune of France, in the Auvergne-Rhône-Alpes regions of France, region, with a population of 147,284 (2020). Its metropolitan area () had 504,157 inhabitants at the 2018 ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

in the 1960s. The Laschamp event was the first known geomagnetic excursion and remains the most thoroughly studied among the known geomagnetic excursions. It is named after the village of Laschamps, part of the commune of

Saint-Genès-Champanelle Saint-Genès-Champanelle (; ) is a commune in the Puy-de-Dôme department in Auvergne in central France. Population See also *Communes of the Puy-de-Dôme department The following is a list of the 463 communes of the Puy-de-Dôme departme ...

in France.

Background and effects

Since its discovery, the magnetic excursion has been demonstrated in geological archives from many parts of the world. The transition from the normal field to the reversed field lasted approximately 250 years, while the magnetic field remained reversed for approximately 440 years. During the transition, Earth's magnetic field declined to a minimum of 5% of its current strength, and was at about 25% of its current strength when fully reversed. This reduction in geomagnetic field strength resulted in more

cosmic rays Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar ...

reaching the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

, causing greater production of the

cosmogenic isotopes Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an ''in situ'' Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom (s ...

beryllium-10 Beryllium-10 (10Be) is a radioactive isotope of beryllium. It is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen. Beryllium-10 has a half-life of 1.39 million years, and decays by beta decay to stable bor ...

and

carbon-14 Carbon-14, C-14, C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic matter is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...

, a

decrease A decrease in knitting Knitting is a method for production of textile Knitted fabric, fabrics by interlacing yarn loops with loops of the same or other yarns. It is used to create many types of garments. Knitting may be done Hand knitting, b ...

in atmospheric ozone, and changes in atmospheric circulation. This loss of the geomagnetic shield has been claimed to have contributed to the extinction of

Australian megafauna The term Australian megafauna refers to the megafauna in Australia (continent), Australia during the Pleistocene, Pleistocene Epoch. Most of these species became extinct during the latter half of the Pleistocene, as part of the broader global L ...

, the extinction of the

Neanderthals Neanderthals ( ; ''Homo neanderthalensis'' or sometimes ''H. sapiens neanderthalensis'') are an extinction, extinct group of archaic humans who inhabited Europe and Western and Central Asia during the Middle Pleistocene, Middle to Late Plei ...

and the appearance of

cave art In archaeology, cave paintings are a type of parietal art (which category also includes petroglyphs, or engravings), found on the wall or ceilings of caves. The term usually implies prehistoric art, prehistoric origin. These paintings were often c ...

. However, the lack of corroborating evidence of a causal link between the Laschamp event and

population bottleneck A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, wid ...

s of many megafauna species, and the relatively moderate radio-isotopic changes during the event, have cast significant doubt on the real impact of the Laschamp event on global environmental changes. Because it occurred approximately 42,000 years ago, the period has been termed the Adams Event or Adams Transitional Geomagnetic Event, a tribute to

science fiction Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...

writer

Douglas Adams Douglas Noel Adams (11 March 1952 – 11 May 2001) was an English author, humorist, and screenwriter, best known as the creator of ''The Hitchhiker's Guide to the Galaxy''. Originally a 1978 BBC radio comedy, ''The Hitchhiker's Guide to the ...

, who wrote in ''

The Hitchhiker's Guide to the Galaxy ''The Hitchhiker's Guide to the Galaxy'' is a Science fiction comedy, comedy science fiction franchise created by Douglas Adams. Originally a The Hitchhiker's Guide to the Galaxy (radio series), radio sitcom broadcast over two series on BBC ...

'' that "42" was the answer to life, the universe and everything.

Research

The Australian Research Council funded research to analyze a kauri tree found in New Zealand in 2019.

Radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...

revealed that the tree was alive from 42,500–41,000 years ago, within the timeframe of the event.

Background and effects

Research

See also

External links

Notes

References