The collision of a sizable fragment of interplanetary rock or metal with Earth's surface after surviving its fiery passage through the atmosphere, ranging from small stones that leave only a modest crater to rare, colossal impacts capable of reshaping the regional or global environment. Meteor Crater in Arizona remains one of the best-preserved impact craters on Earth, while the much larger Chicxulub impact 66 million years ago is widely linked to the mass extinction that ended the age of the non-avian dinosaurs.
Facts
PeriodicityKilometer-scale asteroid strikes about every 500,000 years on average; 4 meter stony asteroids enter the atmosphere about once a year 1 ScaleRanges from small stones to the Chicxulub crater, about 180 km in diameter 1 First DescribedImpact origin of craters conclusively proved in 1963 by Eugene Shoemaker; Barringer Crater identified as an impact crater in 1903-1905 1 Sources
1. Impact event, Wikipedia
Frequency and risk
Asteroids with a 1 km (3,280 ft) diameter strike Earth every 500,000 years on average.
Chicxulub crater paragraph
a crater estimated to be 180 km (110 mi) in diameter
History of recognition of impact craters
it was not until as recently as 1963 that research by Eugene Merle Shoemaker conclusively proved this hypothesis.
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