January 22, 2017

Meteor Crater

Meteor Crater

Meteor Crater is a meteorite impact crater approximately 37 miles (60 km) east of Flagstaff and 18 miles (29 km) west of Winslow in the northern Arizona desert of the United States. Because the United States Board on Geographic Names commonly recognizes names of natural features derived from the nearest post office, the feature acquired the name of "Meteor Crater" from the nearby post office named Meteor. The site was formerly known as the Canyon Diablo Crater and fragments of the meteorite are officially called the Canyon Diablo Meteorite. Scientists refer to the crater as Barringer Crater in honor of Daniel Barringer, who was first to suggest that it was produced by meteorite impact. The crater is privately owned by the Barringer family through their Barringer Crater Company, which proclaims it to be the "best preserved meteorite crater on Earth".

Despite its importance as a geological site, the crater is not protected as a national monument, a status that would require federal ownership. It was designated a National Natural Landmark in November 1967.

Meteor Crater lies at an elevation of about 1,740 m (5,710 ft) above sea level. It is about 1,200 m (3,900 ft) in diameter, some 170 m (560 ft) deep, and is surrounded by a rim that rises 45 m (148 ft) above the surrounding plains. The center of the crater is filled with 210–240 m (690–790 ft) of rubble lying above crater bedrock. One of the interesting features of the crater is its squared-off outline, believed to be caused by existing regional jointing (cracks) in the strata at the impact site.

The crater was created about 50,000 years ago during the Pleistocene epoch, when the local climate on the Colorado Plateau was much cooler and damper. The area was an open grassland dotted with woodlands inhabited by woolly mammoths and giant ground sloths.

Since the crater's formation, the rim is thought to have lost 15–20 m (49–66 ft) of height at the rim crest due to natural erosion. Similarly, the basin of the crater is thought to have approximately 30 m (98 ft) of additional post-impact sedimentation from lake sediments and of alluvium. These erosion processes are the reason that very few remaining craters are visible on Earth, since many have been erased by these geological processes. The relatively young age of Meteor Crater, paired with the Arizona climate, have allowed this crater to remain almost unchanged since its formation. The lack of erosion that preserved the crater's shape helped lead to this crater being the first crater recognized as an official impact crater from a natural celestial body.

The object that excavated the crater was a nickel-iron meteorite about 50 meters (160 feet) across. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at up to 20 kilometers per second (12 miles per second) but more recent research suggests the impact was substantially slower, at 12.8 kilometers per second (8.0 miles per second). It is believed that about half of the impactor's bulk was vaporized during its descent. Impact energy has been estimated at about 10 megatons. The meteorite was mostly vaporized upon impact, leaving little remains in the crater.

Image Credit: National Map Seamless Server
Explanation from: https://en.wikipedia.org/wiki/Meteor_Crater

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