Meteor Crater


Early in the history of the solar system, when space was cluttered with the
materials of its formation, the planets and their moons were heavily bombarded
by meteorites. Some of the members of the solar system (Mars, Mercury and our
moon, for example) still show the residuals of the primordial rain of iron and
stone. On our dynamic planet earth, erosion by weather, water and ice and the
continuous reshuffling of crustal plates have erased most of the evidence of
that early cratering. The solar system, not yet completely clear of the cosmic
debris which was left over at its birth, continued to rain small meteorites down
upon the planets, and occasionally the earth is struck by an object large enough
to excavate a sizable hole. Dozens of meteorite impact craters have been
recognized on the crust of the earth. In most cases, erosion has removed all but
the shattered root zones of the craters. The most famous terrestrial impact
crater is in the desert near Winslow, Arizona. Origin of Meteor Crater What
happens when an irresistible force meets an immovable object? Meteor Crater!

50,000 years ago, a huge iron-nickel meteorite, hurtling at about 40,000 miles
per hour, struck the rocky plain of Northern Arizona with an explosive force
greater than 20 million tons of TNT. The meteorite estimated to have been about

150 feet across and weighing several hundred tons, in less than a few seconds,
left a crater 700 feet deep and more than 4000 thousand feet across. Large
blocks of limestone, some of them, the sizes of small houses were heaved onto
the rim. Flat-lying beds of rock in the crater walls were overturned in
fractions of a second and uplifted permanently as much as 150 feet. Today, the
crater is 550 feet deep, and 2.4 miles in circumference. Twenty football games
could be played simultaneously on its floor, while more than two million
spectators observed from its sloping sides. In 1902, Daniel Moreau Barringer, a

Philadelphia mining engineer, became interested in the site as a potential
source for mining iron. He later visited the crater and was convinced that it
had been formed by the impact of a large iron meteorite. He further assumed that
this body was buried beneath the crater floor. Barringer was correct. The crater
was formed by a meteorite impact, but what he did not know was that the
meteorite underwent total disintegration during impact through vaporization,
melting and fragmentation. In 1903, he formed the Standard Iron Company and had
four placer mining claims filed with the federal Government, thus obtaining the
patents and ownership of the two square miles containing the crater. Barringer
spent the next 26 years attempting to find what he believed would be the giant
iron meteorite. Barringer never found what he was looking for, but he did
eventually prove to the scientific community that the crater was the site of a
meteorite impact. ATextbooks are concerned with presenting the facts of the case
(whatever the case may be) as if there can be no disputing them, as if they are
fixed & immutable. And still worse, there is usually no clue given as to who
claimed these are the facts of the case, or how Ait@ discovered these facts
(there being no he or she, I or we). There is no sense of the frailty or
ambiguity of human judgment, no hint of the possibilities of error. Knowledge is
presented as a commodity to be acquired, never as human struggle to understand,
to overcome falsity, to stumble toward the truth.@ -Neil Postman. The End of

Education Grove Karl Gilbert, the first person to conduct a full scientific
survey of the mysterious crater in the Arizona desert, was the most renown
geologist of his generation, and has been described as Aperhaps the closest
equivalent to a saint that American science has yet produced. (Hoyt, p37) He was
tolerant, generous, and fair-minded, with an intense dislike of controversy of
any kind. As chief geologists of the U.S. Geological Survey, his prestigious
demeanor was held in high esteem. such that none of his colleagues or successors
were willing to publicly question his conclusions-even when it became apparent
that some of those conclusions had been wrong. In 1891, Gilbert became
interested in reports of a large collection of nickel-iron meteorites found in
the neighborhood of a gigantic circular crater in the Arizona desert. Since he
had already speculated on the possible consequences of al large meteorite
striking the earth, he decided to visit the crater and try to determine had it
been the result of such an impact. Gilbert=s methodical approach to research,
considered two alternative hypotheses for the formation of the crater. First
that it had been formed by a meteorite, second, that is was he result of a
massive explosion of steam, produced by volcanic heat at a great distance below
the surface. The idea that it might be an actual volcanic crater was ruled out
by the absence of any volcanic rocks at the site. In his expedition to the
crater (then called Coon Butte or Coon Mountain) in October of 1891, he devised
two tests of the impact hypothesis. First, he reasoned that if the crater had
been produced by an explosion, he material ejected from it would be equal in
volume to the crater=s hollow, If it had been produced by a meteorite, on the
other hand, the meteorite would still be there. Lacking our modern understanding
the mechanics of impact at planetary speeds, Gilbert assumed that the size of
the meteorite would be similar to the size of the crater, and that it would fill
a substantial portion of the hollow, The volume of the hollow would thus be
smaller than that of the ejected material on the rim. The second test involved
the supposed magnetic effect of a large volume of buried iron. If a mass of iron
large enough to produce the crater was still present below the surface, its
attraction would affect the direction of a compass needle, creating local
anomalies. Both tests turned up negative. The volume of material in the crater
rim jut equaled the volume removed from the hole. A variety of experiments with
magnets produced no indication of a large mass of buried iron. The idea of a
volcanic steam explosion was thus, in Gilbert=s view, the Aonly surviving
hypothesis.@ The presence of meteorites in the vicinity of the crater was simply
a coincidence. Gilbert used his investigation of the crater, and his own
abandonment of the impact hypothesis, in a series of 1895 lectures illustrating
the application of the dispassionate scientific approach. It was left to an
inherently different personality to demonstrate the limitations of that
approach. There are only three different types of rocks represented at Meteor

Crater. Just under the topsoil is the dark reddish brown Moenkopi sandstone.

Below the Moenkopi are the yellow and orange layers of the Kaibab limestone. For
several hundred feet below the Kaibab limestone there is only Coconino
sandstone. It is this grayish rock which is seen making up most of the crater
walls. It is pulverized Coconino which is white that was dug up in the first
shafts . Piles of this white silica are very obvious on the crater floor still
today. The Kaibab limestone at the crater contain a variety of fossils. (See
attached photos) The layers of rock all around the crater rim have been uplifted
and tilted, however, at the south cliffs the rock are vertical. It has been
suggested that the force exerted on the south cliffs 0was greater because of the
distance to the focus of the explosion was shorter. If the body of the asteroid
came to a stop and released its kinetic energy under the south cliffs they would
be closest to the focus. Barringer was convinced that the remaining body of
metal was under the south rim. The drill on the south rim hit something
meteoric. The rocks of the south cliffs and rim are also displaced much more
than the rest of the rim. Weighing in at over 1,400 pounds, the Holsinger

Fragment is the largest of the meteorites found at Meteor Crater. Named for

Samuel Holsinger who had been Barringer Foreman and drill supervisor for many
years it now rests in the museum on the crater rim. Like many of the Canyon

Diablo meteorites, it has holes in it. Some of these holes were probably
graphite nodules burned away. Nodules of graphite are very common in Canyon

Diablo meteorites. The topographical terrain of Meteor Crater so closely
resembles that of the earth=s moon and other planets, NASA designated it as one
of the official training sites for the Apollo Astronauts. The US Government
deemed the crater a Natural Landmark in 1968. It is still privately owned by the

Barringer family. They lease the crater to Meteor Crater Enterprises, who
operate the visitors center at the crater.

Bibliography

Hoyt, William, Coon Mountain Controversies, Tucson, University of Arizona

Press, 1987; 423 p Mark, Kathleen, Meteorite Craters, Tucson, University of

Arizona press, 1987; 247 p Smith, Dean, The Meteor Crater Story, (Meteor Crater

Enterprises Inc) Flagstaff, Arizona Abrahams, Harold J , Heroic Efforts at

Meteor Crater, Arizona. (N.J. Associated University Presses, Inc., 1983; 315 p

Rabinowitz, Carla Barringer, The Adventure Daniel Moreau Barringer and the

Battle for the Impact Theory, : http://www.barringercrater.com/adventure/main.htm