http://en.wikipedia.org/wiki/Impact_eventAn impact event is the collision of an asteroid, comet, or other celestial object with another celestial object such as Earth. Throughout recorded history, hundreds of minor impact events (and exploding bolides) have been reported, with some occurrences causing deaths, injuries, property damage or other significant localised consequences.[1] There have also been major impact events throughout the Earth's history which severely disrupted the environment and caused mass extinctions. Impact craters are the result of impact events on solid objects and as the dominant landforms on many of the System's solid objects and provide the most solid evidence of prehistoric events.
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Small objects frequently collide with Earth. There is an inverse relationship between the size of the object and the frequency that such objects hit Earth. The lunar cratering record shows that the frequency of impacts decreases as approximately the cube of the resulting crater's diameter, which is on average proportional to the diameter of the impactor.[2] Asteroids with a 1 km (0.62 mi) diameter strike Earth every 500,000 years on average.[3] Large collisions – with 5 km (3 mi) objects – happen approximately once every twenty million years.[4] The last known impact of an object of 10 km (6 mi) or more in diameter was at the Cretaceous–Paleogene extinction event 66 million years ago.[5]
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Modern Impact EventsOne of the best-known recorded impacts in modern times was the Tunguska event, which occurred in Siberia, Russia, in 1908. This incident involved an explosion that was probably caused by the airburst of an asteroid or comet 5 to 10 km (3.1 to 6.2 mi) above the Earth's surface, felling an estimated 80 million trees over 2,150 km2 (830 sq mi).
In 1913 a ship was reported to have been struck and damaged by a meteorite while sailing between Sydney and South America.[33]
The first known modern strike to a human was on the April 28, 1927 in Aba, Japan, to the head of the five-year-old daughter of Mrs. Kuriyama; a bean-sized stone was found resting on her headband and now resides in a museum, called the Aba stone.[34] The girl recovered several days later.[34]
The first known modern case of a human injured by a space rock occurred on November 30, 1954, in Sylacauga, Alabama.[35] There a 4 kg (8.8 lb) stone chondrite crashed through a roof and hit Ann Hodges in her living room after it bounced off her radio. She was badly bruised. Several persons have since claimed to have been struck by 'meteorites' but no verifiable meteorites have resulted.
Topic: Metorite falls in Russia - over 500 wounded as I am writing (Read 7809 times)