Meteor Crater Essay, Research Paper

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.

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