The Ordovician meteor event was a dramatic increase in the rate at which

L chondrite The L type ordinary chondrites are the second most common group of meteorites, accounting for approximately 35% of all those catalogued, and 40% of the ordinary chondrites. The ordinary chondrites are thought to have originated from three parent a ...

meteorites fell to Earth during the

Middle Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The ...

period, about 467.5±0.28 million years ago. This is indicated by abundant fossil L chondrite meteorites in a quarry in Sweden and enhanced concentrations of ordinary chondritic

chromite Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of FeCr2O4. It is an oxide mineral belonging to the spinel group. The element magnesium can s ...

grains in sedimentary rocks from this time. This temporary increase in the impact rate was most likely caused by the destruction of the L chondrite parent body 468 ± 0.3 million years ago having scattered fragments into Earth-crossing orbits, a chronology which is also supported by shock ages in numerous L chondrite meteorites that fall to Earth today. It has been speculated that this influx contributed to, or possibly even instigated, the

Great Ordovician Biodiversification Event The Great Ordovician Biodiversification Event (GOBE), was an evolutionary radiation of animal life throughout the Ordovician period, 40 million years after the Cambrian explosion, whereby the distinctive Cambrian fauna fizzled out to be replaced wi ...

, although this has been questioned.An extraterrestrial trigger for the mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body

Birger Schmitz Birger is a Scandinavian name from Old Norse, ''bjarga'', meaning "to help, to save, to protect". It is widely used in Norway as Birger but also as Børge. The Swedish variant of ''Birger'' would soon evolve into ''Börje'', however, the prior form ...

et al, AAAS

Science Advances ''Science Advances'' is a peer-reviewed multidisciplinary open-access scientific journal established in early 2015 and published by the American Association for the Advancement of Science. The journal's scope includes all areas of science, incl ...

, 18 Sep 2019: Vol. 5, no. 9, eaax4184; DOI: 10.1126/sciadv.aax4184, accessed 2019-10-09

Possible craters

References

{{Impact cratering on Earth

Meteor A meteoroid () is a small rocky or metallic body in outer space. Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...

Impact craters of Canada Impact craters of Sweden Impact craters of the United States

Possible craters

See also

References