Meteor Crater, AZ 2010
While driving on I-40 in December of 2010, (1 hour east of Flagstaff), I took exit 233 to visit the Barringer Meteorite Crater.
Commonly known simply as Meteor Crater, the Barringer Meteorite Crater is 1360 meters across and 190 m deep. A rim surrounding the crater rises 20-60 m above the flat plateau and is composed of jumbled rock fragments ranging from particles as small as 1 micrometer to boulders as big as houses.
Meteor Crater formed when the Canyon Diablo Meteor struck the Earth 49,300 years ago at a speed of 45,000 km/hr. The blast was at least equivalent to a 2.5 megaton bomb.
The origin of Meteor Crater was controversial for many years in 1891, G.K. Gilbert, the director of the U.S. Geological Survey, “proved” a volcanic origin for the crater and stated that the meteorites found around the crater were there by coincidence. Geologist D.M. Barringer felt otherwise.
In 1902, D.M. Barringer established the Standard Iron company to mine the iron-nickel meteorite that he thought would be buried in the crater, although as it turned out it was mostly vaporized on impact.
Barringer continued to convince other scientists of the astronomical origin of the crater for the rest of his life. Most remained skeptical. It wasn’t until 1963 that a publication by astro-geologist E.M. Shoemaker convinced people that a meteor blasted out the crater.
Shoemaker presented 2 main pieces of evidence. 1) The rim around the crater is composed of the same rock formations that underlie the surrounding Colorado Plateau, except that they are upside-down. [This could only happen if a shockwave shattered, uplifted, and overturned the rocks]. 2) Coesite and stishovite were found in the sandstone blasted by the impact. [Both are denser type of quartz that only form due to the greater pressures of an Meteorite Impact].
The size of the original meteor remains a mystery. However, it is estimated by planetary astronomers to have been 10-50 m in diameter.
The original impact vaporized much of the meteor. The remainder was shattered into billions of pieces and spread out over more than 180 square kilometers. Only 30 tons out of the original 300,000 tons of fragments have been collected.