Barringer Crater

For the crater on the Moon, see the Lunar Barringer crater

The Barringer Crater, also known as the Meteor Crater, is a famous impact crater created by a meteorite, located about 55 kilometers east of Flagstaff in the northern Arizona desert (USA). Its coordinates are Template:Coor dms

The impact of the meteor with Earth occurred about 50,000 years ago. Currently, the crater is about 1.5 kilometers in diameter (slightly less than a mile), and some 170 meters deep (570 feet). A 30 meter high rim of rock surrounds the crater, distinguishing it from the surrounding plains. The impact happened during the Pleistocene when the climate on the Colorado Plateau was cooler and damper. The area was a grassland dotted with woodlands inhabited by wooly mammoths, giant ground sloths, and camels. No humans would have been anywhere nearby; the first humans are thought to have reached the continent around 13,000 years ago.

The crater was created when an iron-metallic meteor about 50 meters across fell from the sky. For any creatures watching, it would have burned much brighter than the Sun as it fell. Previously, it was thought that the meteor reached 45,000 miles an hour (72,000 km/h) at impact, although the most recent analysis, in the March 10, 2005 edition of Nature, suggests the impact was at 28,600 miles per hour (12 km/s), substantially slower than previously thought, and approximately half of the rock's 300,000-ton mass vaporized during the descent. The impact produced a massive explosion equivalent to at least 2.5 megatons of TNT - equivalent to a large thermonuclear explosion and about 150 times the yield of the atomic bombs used at Hiroshima and Nagasaki. The explosion dug out 175 million tons of rock and left a crater about 1,200 meters across and 170 meters deep. The shock of impact propagated as a hemispherical shock wave that blasted the rock down and outward from the point of impact, forming the crater. Much more impact energy, equivalent to an estimated 6.5 megatons, was released into the atmosphere and generated a devastating above-ground shockwave.

For a meteor of its size, the impact melted surprisingly little rock, though it produced high enough temperatures and pressures to transform carbon minerals into diamonds and lonsdaleite, a form of diamond found near the crater in fragments of Arizona's Canyon Diablo meteorite. The lower temperature than expected is a result of increased air resistance when the meteor broke into fragments, slowing the meteor and preventing it from heating, according to a March 10, 2005 paper in Nature. Limestone blocks as massive as 30 tons were tossed outside the crater's rim. The shock of the impact would have sped through the ground, resulting in an earthquake of magnitude 5.5 or higher.

All life within a radius of three to four kilometers was killed immediately. The fireball that formed would have scorched everything within a radius of ten kilometers. A shock wave moving out at 2,000 km/h leveled everything from 14 to 22 kilometers, dissipating to hurricane-force winds that persisted to a radius of 40 kilometers. Despite this destruction, the Barringer impact did not throw up enough dust to seriously affect the Earth's climate. The area was likely recolonized by the local flora and fauna within a century.

Discovery

Settlers in the American West were the first to find the great crater. At first, some geologists believed it was a volcanic crater, but in 1903 a mining engineer and businessman named Daniel Moreau Barringer suggested it was the result of the impact of a large iron-metallic meteorite. Barringer's company, the Standard Iron Company, conducted research on the crater between 1903 and 1905, and concluded that the crater had indeed been caused by a violent impact. Barringer and his partner, the mathematician and physicist Benjamin C. Tilghman, presented their first papers to the U.S. Geological Survey in 1906, outlining the evidence in support of the impact theory. The papers were published in the Proceedings of the Academy of Natural Sciences in Philadelphia. Later research by Eugene M. Shoemaker would confirm his hypothesis, as the crater was lined with materials showing the effects of the enormous pressures and high temperatures associated with an impact event. It is the first site to be proven to be formed by the impact of an object from outer space.

At the time of first discovery by Europeans, the surrounding plains were covered with about 30 tons of oxidized iron chunks from the meteorite. Barringer spent 27 years trying to mine the crater and find metallic iron, which he believed to have been left by the meteorite. However, as the meteorite had vaporized on impact, no significant deposit was ever found.

External links

• Barringer Crater official site (http://barringercrater.com)
• CNN: New computer analysis (http://www.cnn.com/2005/TECH/space/03/09/arizona.meteor.crater/index.html) shows that the meteor may have been traveling more slowly than previously thought
• Google Map (http://maps.google.com/maps?q=Winslow,+AZ&ll=35.028448,-111.022253&spn=0.067291,0.095615&t=k&hl=en)de:Barringer-Krater

fr:Meteor Crater nl:Barringerkrater ja:バリンジャー・クレーター pl:Meteor Crater ru:Аризонский кратер