The Laschamp or Laschamps 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 "permanent" re-orientation of the large-scale field, but rather represents a dramatic, typic ...
(a short reversal of the Earth's magnetic field). 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
Clermont-Ferrand (, ; ; oc, label=Auvergnat, Clarmont-Ferrand or Clharmou ; la, Augustonemetum) is a city and commune of France, in the Auvergne-Rhône-Alpes region, with a population of 146,734 (2018). Its metropolitan area (''aire d'attract ...
,
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
in the 1960s.
The Laschamp event was the first known geomagnetic excursion and remains the most thoroughly studied among the known geomagnetic excursions.
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 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 System in our ow ...
reaching the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
, causing greater production of the
cosmogenic isotopes 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 × 106 years, and decays by beta decay to stable boron- ...
and
carbon-14, a
decrease in
atmospheric ozone, and changes in atmospheric circulation.
This loss of the geomagnetic shield is claimed to have contributed to the extinction of
Australian megafauna
The term Australian megafauna refers to the megafauna in Australia during the Pleistocene Epoch. Most of these species became extinct during the latter half of the Pleistocene, and the roles of human and climatic factors in their extinction are ...
, the extinction of the
Neanderthals and the appearance of
cave art.
However, the lack of corroborating evidence of a causal link between the Laschamp event and
population bottlenecks 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 (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...
writer
Douglas Adams
Douglas Noel Adams (11 March 1952 – 11 May 2001) was an English author and screenwriter, best known for ''The Hitchhiker's Guide to the Galaxy''. Originally a 1978 The Hitchhiker's Guide to the Galaxy (radio series), BBC radio comedy, ''The H ...
, who wrote in ''
The Hitchhiker's Guide to the Galaxy
''The Hitchhiker's Guide to the Galaxy'' (sometimes referred to as ''HG2G'', ''HHGTTG'', ''H2G2'', or ''tHGttG'') is a comedy science fiction franchise created by Douglas Adams. Originally a 1978 radio comedy broadcast on BBC Radio 4, it ...
'' that "42" was the answer to life, the universe and everything.
Research
The Australian Research Council is funding research to analyze a
kauri tree found in New Zealand in 2019.
Radiocarbon dating reveals that the tree was alive from 42,500–41,000 years ago, within the timeframe of the event.
See also
*
Solar cycle
The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surfa ...
*
Solar cycle 1
Notes
:1. The name derives from the Laschamps lava flows from which it was discovered, but appears as 'Laschamp' in most scientific literature.
References
{{Reflist
Geomagnetic reversal
Pleistocene events