Around this strange crater of unknown origins, chunks of iron were found. Since , nearly 2, fragments of an almost pure iron-nickel alloy had been recovered, which are now referred to today as Canyon Diablo iron.
Hoping to find a larger mass of iron underground, Barringer acquired the mining rights for the land. Aerial view of Arizona Meteor Crater, September Source and Credit Wikipedia user CC BY 3. At the time the existence of iron meteorites, material coming from outer space to Earth , was known for almost one century.
In the German naturalist Ernst Friedrich Chladni described the chemical properties of particular pieces of iron, collected all over the world. He demonstrated that this metal showed significant chemical differences if compared with rocks or minerals as found on Earth, proving its extraterrestrial origin. However, at the beginning of the 20th century, no confirmed impact structure, formed by the impact of large meteorites on Earth's surface, was known.
In , geophysicist Alfred Wegener, of continental drift fame , published his observation about craters. Measuring various craters, he noted a distinct difference between craters of doubted origin and confirmed volcanic craters. Some craters are very wide, relatively flat, sometimes showing a central peak and outer rings, surrounding the central crater. Using such parameters, Wegener demonstrated in that a strange crater on the island of Saaremaa in the Baltic Sea was not a volcano or the result of a gas explosion, but formed when a meteorite hit Earth.
Unfortunately, like Wegener's other great idea , his impact theory wasn't taken seriously until the s. The probable sum of these effects is the destruction of vegetation over an area to km 2. Damage to vegetation would have extended over an additional to km 2. While these effects are severe, they are confined to the immediate region and did not cause extinctions. In fact, the newly formed bowl shaped depression soon filled with water providing a lake habitat see graphic for aquatic plants and animals.
These types of events, however, are large enough to destroy a modern city. They occur at an average rate of about once in years. Meteorites are named for the nearest geographical feature.
In the earliest years that was Canyon Diablo just to the west of Meteor Crater. When Holsinger died a few months later in August of Barringer named the lbs kgs iron he had found The Holsinger Meteorite. Meteor Crater has often been referred to as Barringer Crater by scientists. Fine silica flour created by the cosmic hammer blow occurs in vast quantities around Meteor Crater. But despite many samples being sent to manufacturers during his lifetime none ever lead to a commercial product.
Barringer expended great effort trying to find investors to fund his search for the buried iron. After months of preparation work drilling started with a 10 inch churn drill bit on November 1, Progress in the drilling was fantastic at first, with the drill reaching 97 feet But soon the creviced and shattered rocks of Meteor Crater would turn the drilling program into a costly nightmare which lasted for two years.
Little evidence of meteoric material was discovered during the drilling on the south rim. Two objects that were nearly as hard as the drill bit were ground through with great difficulty. They were each just a few feet thick and may have been iron meteorite fragments.
In the last few feet before the drill became stuck for the last time they had reached an area where weathered meteoritic material was being brought to the surface. But no great mass of millions of tons was ever found. Barringer took the small amount of evidence that the drill had revealed and began an even more costly and futile effort. He started tunneling to the area the drill had found. From a location about feet m south of the drill hole out on the slope he began the final shaft.
He proposed to dig down to the depth where the drill had encountered the meteoric material. This was over feet m and then tunnel horizontally over to the mass. He had long believed that the water which had plagued the previous shafts was confined to the crater. He was to discover that it was not. At around feet m they hit water again.
Larger and larger pumps were obtained and millions of gallons of water were removed. They cemented the walls of the shafts as they descended. The miners struggled down to feet m with enormous effort. After weeks of more effort they had gained just a few more feet when the pump broke down and the shaft flooded.
At a final depth of about feet m this shaft was also abandoned. It would be the last major attempt to find the buried asteroid. Although this idea held fast for the next two decades, a major change in scientific thinking was about to occur. In , Daniel Moreau Barringer, a Philadelphia mining engineer, had become 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 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. This was ten years before Arizona became the 48th state.
What he did not know was that the meteorite underwent total disintegration during the impact through vaporization, melting and fragmentation. There was never a single large mass buried beneath the crater. In , Barringer came to Meteor Crater and spent the next 26 years attempting to find what he believed would be the giant iron meteorite. For the next two-and-a-half decades, his work and scientific research were carried on with great perseverance and bitter disappointment.
Since the crater is roughly circular, it was natural at that time to assume that the body that formed it lay beneath its center. Consequently, the first shaft was started where the low, white mounds of pulverized Coconino sandstone can still be seen on the crater floor. A few small meteoritic fragments were reported in the shaft, but unfortunately, the pulverized rock beneath the water table turned to quicksand and prevented mining to a depth where the main body was suspected to lie.
After the initial exploration, Barringer conducted some simple experiments and discovered that a rifle bullet fired into thick mud, even at a low angle, generally produces a round hole.
This was an important clue Looking at the south crater wall you will see, as did Barringer, that the rock is noticeably uplifted. Sandstone and limestone beds, which were once deeply buried are now more that feet above their pre-impact levels. In fact, they are higher than anywhere else in the crater. This observation, coupled with the fact that many meteorite fragments hod been found on the northeast side of the crater, led Barringer to conclude that the mass had come in at an angle from that direction and buried itself beneath the south rim of the crater.
Looking again at the south crater wall, you will see a notch with a streak of red debris running down the slope.
Drilling was started at that notch and at a depth of 1, feet Barringer reported increasing numbers of oxidized meteorite fragments. At times, hours passed with no progress in deepening the hole and the drill bit would gouge into something at least as hard as the drill bit itself. Then at 1, feet, the rotary drill bit jammed completely.
Barringer interpreted this to be caused by meteorite debris. The bit was permanently stuck, the drill cable broke, funds were exhausted, and the exploration was abandoned in Although Barringer died later that year, he lived to see his theory of impact origin accepted.
In , the Barringer family entered into a lease with Bar T Bar Ranch Company, a cattle operation which started in the 's and owns or leases the surrounding lands.
All the facilities at Meteor Crater were built, maintained, and are staffed by the Enterprises. Today, the Barringers still own the land and both the Barringer family and the owners of the Enterprises regard the property as a public trust. Each year both make substantial contributions to science and education through grants, scholarships, and special awards.
Today, modern geological and geophysical exploration techniques have largely replaced the earlier method of just digging shafts and simple rotary drilling. New approaches include the use of seismic, gravity, magnetic, and electrical field techniques. Recently, cosmic ray spallation procedures were used to arrive at a more accurate age of Meteor Crater and C14 dating techniques have been used to address erosion and climatic issues. Advanced microscope, x-ray, and other laboratory procedures are in use to study the shocked rocks, meteoritic material, and their histories.
Geological Survey in Flagstaff, proved in , beyond any doubt that Meteor Crater was indeed the product of a giant impact event. Shoemaker and his wife Carolyn have recently completed a number of studies that provide estimates of the rates and energies associated with comets and asteroids that might impact Earth. For example, a Meteor Crater size event should occur about once every 50, years The U. Geological Survey discovered coesite and stishovite at Meteor Crater.
Both are high-pressure polymorphous forms of silica, or silicon dioxide Si02 , altered to very dense crystalline states by extremely high pressures equivalent to more than 20, times atmospheric pressure, or , pounds per square inch. Although coesite and stishovite can be produced in the laboratory, they had not before been identified in nature.
Since the Meteor Crater research, both minerals have been identified at a number of other geological features called astroblemes. These two high-pressure minerals are now diagnostic criteria proving these sites are the scars of ancient impact craters.
0コメント