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70-399: Meteor Crater lies at an elevation of 5,640 ft (1,719 m) above sea level. It is about 3,900 ft (1,200 m) in diameter, some 560 ft (170 m) deep, and is surrounded by a rim that rises 148 ft (45 m) above the surrounding plains. The center of the crater is filled with 690–790 ft (210–240 m) of rubble lying above crater bedrock. One of the features of

140-424: A nuclear explosion . In 1960, Edward C. T. Chao and Shoemaker identified coesite at Meteor Crater, adding to the growing body of evidence that the crater was formed from an impact generating extremely high temperatures and pressures. He confirmed what F.R. Moulton and H.H. Nininger already proposed: the impact vaporized the vast majority of the impactor. The pieces of Canyon Diablo meteorite found scattered around

210-455: A crater in Arizona, now known as Meteor Crater but then as Coon Butte. For several reasons, and against his intuition, he concluded it was the result of a volcanic steam explosion rather than an impact of a meteorite . Gilbert based his conclusion on the beliefs that the volume of an impact crater including the meteorite should be more than the ejected material on the rim and that, if it was

280-533: A few centimeters to several metres. They are often oriented perpendicular to either the upper surface and base of lava flows and the contact of the tabular igneous bodies with the surrounding rock. This type of jointing is typical of thick lava flows and shallow dikes and sills. Columnar jointing is also known as either columnar structure , prismatic joints , or prismatic jointing . Rare cases of columnar jointing have also been reported from sedimentary strata. Joints can be classified according to their origin, under

350-519: A lava lake or flood basalt flow or the sides of a tabular igneous intrusion into either lava of the lake or lava flow or magma of a dike or sill. Joint propagation can be studied through the techniques of fractography in which characteristic marks such as hackles and plumose structures are used to determine propagation directions and, in some cases, the principal stress orientations. Some fractures that look like joints are actually shear fractures, which in effect are microfaults. They do not form as

420-462: A meteorite, iron should create magnetic anomalies. Gilbert's calculations showed that the crater's volume and the debris on the rim were roughly equal, and that there were no magnetic anomalies. He argued that the meteorite fragments found on the rim were just "coincidence". In 1892, Gilbert delivered his paper "The Moon's Face; A Study of the Origin of Its Features" as his retiring President's lecture to

490-432: A result of vertical gravitational loading. In simple terms, the accumulation of either sediments, volcanic, or other material causes an increase in the pore pressure of groundwater and other fluids in the underlying rock when they cannot move either laterally or vertically in response to this pressure. This also causes an increase in pore pressure in preexisting cracks that increases the tensile stress on them perpendicular to

560-600: A study of the former ancient Lake Bonneville in 1890 (the lake existed during the Pleistocene ), of which the Great Salt Lake is a remnant. He named it after the army captain Benjamin Bonneville , who had explored the region. The type of river delta that Gilbert described at this location has since become known to geomorphologists as a Gilbert delta . In 1891, Gilbert examined the origins of

630-478: A tectonic - hydraulic hybrid. Exfoliation joints are sets of flat-lying, curved, and large joints that are restricted to massively exposed rock faces in a deeply eroded landscape. Exfoliation jointing consists of fan-shaped fractures varying from a few meters to tens of meters in size that lie sub-parallel to the topography. The vertical, gravitational load of the mass of a mountain-size bedrock mass drives longitudinal splitting and causes outward buckling toward

700-435: Is a significant part of understanding the geology and geomorphology of an area. Joints often impart a well-develop fracture-induced permeability to bedrock. As a result, joints strongly influence, even control, the natural circulation ( hydrogeology ) of fluids, e.g. groundwater and pollutants within aquifers , petroleum in reservoirs , and hydrothermal circulation at depth, within bedrock. Thus, joints are important to

770-488: Is an important part of finding and profitably developing ore deposits. Finally, joints often form discontinuities that may have a large influence on the mechanical behavior (strength, deformation, etc.) of soil and rock masses in, for example, tunnel , foundation , or slope construction. As a result, joints are an important part of geotechnical engineering in practice and research. Grove Karl Gilbert Grove Karl Gilbert (May 6, 1843 – May 1, 1918), known by

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840-426: Is considered one of the giants of the subdiscipline of geomorphology , having contributed to the understanding of landscape evolution, erosion , river incision, and sedimentation . He was a planetary science pioneer, correctly identifying lunar craters as caused by impacts, and carrying out early impact-cratering experiments. He coined the term sculpture for a pattern of radial ridges surrounding Mare Imbrium on

910-609: The Rocky Mountain Region in 1874, becoming Powell's primary assistant, and stayed with the survey until 1879. During this time he published an important monograph, The Geology of the Henry Mountains (1877). After the U.S. Geological Survey was created in 1879, he was appointed to the position of Senior Geologist and worked for the USGS until his death (including a term as acting director). Gilbert published

980-526: The "best-preserved meteorite crater on Earth". It was designated a National Natural Landmark in November 1967. 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 mammoths and giant ground sloths . The object that excavated

1050-555: The Earth. In 1942, Nininger moved his home and business from Denver to the Meteor Crater Observatory, located near the turn-off for Meteor Crater on Route 66 . He christened the building the "American Meteorite Museum" and published a number of meteorite and Meteor Crater-related books from the location. He also conducted a wide range of research at the crater, discovering impactite, iron-nickel spherules related to

1120-532: The Museum of Astrogeology , the Visitor Center includes a Discovery Center & Space Museum, a movie theater, a gift shop, and observation areas with views inside the rim of the crater. Guided tours of the rim are offered daily, weather permitting. Joint (geology) A joint is a break ( fracture ) of natural origin in a layer or body of rock that lacks visible or measurable movement parallel to

1190-606: The Philosophical Society of Washington, and it was published in the Society's bulletin. He publicized these conclusions in a series of lectures in 1895. Later investigations revealed that it was in fact a meteor crater, but that interpretation was not well established until the mid-20th century. As part of his interest in crater origins, Gilbert also studied the moon's craters and concluded they were caused by impact events rather than volcanoes, although he wondered why

1260-558: The [Barringers] would be receptive to a fair purchase for the crater." By this time, mining activity at the crater had ceased, and the Barringers were in the process of planning a tourist attraction on the rim of the crater. Nininger was operating the American Meteorite Museum nearby, on Route 66, at the time. Nininger hoped that a public museum could be built on the crater's rim, and that the project might lead to

1330-659: The abbreviated name G. K. Gilbert in academic literature, was an American geologist . Gilbert was born in Rochester, New York , and graduated from the University of Rochester . During the American Civil War , he was twice listed for the draft, but his name was drawn neither time. In 1871, he joined George M. Wheeler 's geographical survey as its first geologist. Gilbert joined the Powell Survey of

1400-411: The angle at which joint sets of systematic joints intersect to form a joint system, systematic joints can be subdivided into conjugate and orthogonal joint sets. The angles at which joint sets within a joint system commonly intersect are called dihedral angles by structural geologists. When the dihedral angles are nearly 90° within a joint system, the joint sets are known as orthogonal joint sets . When

1470-595: The associated physical and dynamical processes accounting for their evolving structure and morphology." Meteor Crater is a popular tourist destination with roughly 270,000 visitors per year. The crater is owned by a family company, the Barringer Crater Company. Meteor Crater is an important educational and research site. It was used to train Apollo astronauts and continues to be an active training site for astronauts. The Meteor Crater Visitor Center sits on

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1540-638: The atmosphere. Impact energy has been estimated at 10 megatons TNT e . The meteorite was mostly vaporized upon impact, leaving few remains in the crater. Since the crater's formation, the rim is thought to have lost 50–65 ft (15–20 m) of height at the rim crest as a result of natural erosion . Similarly, the basin of the crater is thought to have roughly 100 ft (30 m) of additional postimpact sedimentation from lake sediments and alluvium . Very few remaining craters are visible on Earth, since many have been erased by erosive geological processes. The relatively young age of Meteor Crater, paired with

1610-409: The crater floor. Impact physics was poorly understood at the time, and Barringer was unaware that most of the meteorite vaporized on impact. He spent 27 years trying to locate a large deposit of meteoric iron , and drilled to a depth of 1,375 ft (419 m), but no significant deposit was ever found. Barringer was politically well-connected. In 1906, at his request, President Roosevelt authorized

1680-573: The crater had been produced by the impact of a large iron meteorite . Barringer's company, the Standard Iron Company, staked a mining claim on the land and received a land patent signed by Theodore Roosevelt for 640 acres (1 sq mi, 260 ha) around the center of the crater in 1903. Barringer had amassed a small fortune as an investor in the successful Commonwealth Mine in Pearce , Cochise County, Arizona . He drew up ambitious plans for

1750-559: The crater is its squared-off outline, believed to be caused by existing regional jointing (cracks) in the strata at the impact site. Despite an attempt to make the crater a public landmark, the crater remains privately owned by the Barringer family to the present day through their Barringer Crater Company. The Lunar and Planetary Institute , the American Museum of Natural History , and other science institutes proclaim it to be

1820-632: The crater rim and in the crater itself, the Winona is mapped in a complex association with rock outcrop. During the 1960s and 1970s, NASA astronauts trained in the crater to prepare for the Apollo missions to the Moon , and ongoing field training for astronauts continues to this day. On August 8, 1964, two commercial pilots in a Cessna 150 flew low over the crater. After crossing the rim, they could not maintain level flight. The pilot attempted to circle in

1890-496: The crater to climb over the rim. During the attempted climb out, the aircraft stalled, crashed, and caught fire. The plane is commonly reported to have run out of fuel, but this is incorrect. Both occupants were severely injured, but survived. A small portion of the wreckage not removed from the crash site remains visible. In 2006, a project called METCRAX (for METeor CRAter eXperiment) investigated "the diurnal buildup and breakdown of basin temperature inversions or cold-air pools and

1960-439: The crater was a nickel - iron meteorite about 160 ft (50 m) across. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at up to 45,000 mph (20 km/s), but more recent research suggests the impact was substantially slower, at 29,000 mph (12.8 km/s). About half of the impactor's bulk is believed to have been vaporized during its descent through

2030-403: The crater. A key discovery was the presence in the crater of the minerals coesite and stishovite , rare forms of silica found only where quartz -bearing rocks have been severely shocked by an instantaneous overpressure. Shocked quartz cannot be created by volcanic action; the only known mechanisms of creating it are naturally through lightning or an impact event , or artificially, through

2100-543: The craters were round and not oval as expected for an oblique impact. The interpretation of lunar craters as of impact origin was also debated until the mid-20th century. Gilbert joined the Harriman Alaska Expedition in 1899. Two weeks after the 1906 San Francisco earthquake , he took a series of photographs documenting the damage along the San Andreas fault from Inverness to Bolinas. Gilbert

2170-412: The dihedral angles are from 30 to 60° within a joint system, the joint sets are known as conjugate joint sets . Within regions that have experienced tectonic deformation, systematic joints are typically associated with either layered or bedded strata that have been folded into anticlines and synclines . Such joints can be classified according to their orientation in respect to the axial planes of

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2240-534: The dry Arizona climate, has allowed this crater to remain comparatively unchanged since its formation. The lack of erosion that preserved the crater's shape greatly accelerated its groundbreaking recognition as an impact crater from a natural celestial body. Meteor Crater came to the attention of scientists after American settlers encountered it in the 19th century. The crater was given several early names, including "Coon Mountain", "Coon Butte", "Crater Mountain", "Meteor Mountain," and "Meteor Crater." Daniel M. Barringer

2310-462: The economic and safe development of petroleum, hydrothermal, and groundwater resources and the subject of intensive research relative to these resources. Regional and local joint systems exert a strong control on how ore-forming hydrothermal fluids (consisting largely of H 2 O , CO 2 , and NaCl — which formed most of Earth's ore deposits ) circulated within its crust. As a result, understanding their genesis, structure, chronology, and distribution

2380-460: The establishment of a post office unconventionally named "Meteor", located at Sunshine, a stop on the Atchison, Topeka and Santa Fe Railway , 6 miles (9.7 km) north of the crater. The Meteor post office closed on April 15, 1912, due to disuse. In 1929, astronomer F.R. Moulton was employed by the Barringer Crater Company to investigate the physics of the impact event. Moulton concluded that

2450-419: The first scientific paper about the meteorites of Northern Arizona. Several years earlier, Foote had received an iron rock for analysis from a railroad executive. Foote immediately recognized the rock as a meteorite and led an expedition to search and retrieve additional meteorite samples. The team collected samples ranging from small fragments to over 600 lb (270 kg). Foote identified several minerals in

2520-559: The folds as they often commonly form in a predictable pattern with respect to the hinge trends of folded strata. Based upon their orientation to the axial planes and axes of folds, the types of systematic joints are: Columnar jointing is a distinctive type of joints that join together at triple junctions either at or about 120° angles. These joints split a rock body into long, prisms or columns. Typically, such columns are hexagonal, although 3-, 4-, 5- and 7-sided columns are relatively common. The diameter of these prismatic columns ranges from

2590-445: The founding of a federal institute of meteorite research. Offended by Nininger's attempt to nationalize the crater, the Barringer family promptly terminated his exploration rights and ability to conduct further fieldwork at the crater. A few years later, in 1953, the Standard Iron Company was renamed the "Barringer Crater Company," and a private museum was constructed on the crater rim. Eugene Merle Shoemaker continued investigations at

2660-460: The free air. In addition, paleostress sealed in the granite before the granite was exhumed by erosion and released by exhumation and canyon cutting is also a driving force for the actual spalling. Unloading joints or release joints arise near the surface when bedded sedimentary rocks are brought closer to the surface during uplift and erosion; when they cool, they contract and become relaxed elastically. A stress builds up which eventually exceeds

2730-524: The idea that Meteor Crater formed by the impact of an asteroid. Many of his discoveries were later observed at other relatively fresh impact craters, including Henbury and Monturaqui . Nininger believed that the crater should be a national monument and, in 1948, he successfully petitioned the American Astronomical Society to pass a motion in support of nationalizing the crater by making "the unauthorized - and false - claim that

2800-403: The impact and vaporization of the asteroid, and the presence of many other features, such as half-melted slugs of meteoric iron mixed with melted target rock. Nininger's discoveries were compiled and published in a seminal work, Arizona's Meteorite Crater (1956). Nininger's extensive sampling and fieldwork in the 1930s and 40s contributed significantly to the scientific community's acceptance of

2870-488: The impactor likely weighed as little as 300,000 tonnes, and that the impact of such a body would have generated enough heat to vaporize the impactor instantly. Barringer died just ten days after the publication of Moulton's second report. By this time, "the great weight of scientific opinion had swung around to the accuracy of the impact hypothesis ... Apparently an idea, too radical and new for acceptance in 1905, no matter how logical, had gradually grown respectable during

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2940-493: The intervening 20 years." Harvey Harlow Nininger was an American meteoriticist and educator , and he revived interest in scientific study of meteorites in the 1930s, and assembled the largest personal collection of meteorites up to that time. While based in Denver , Colorado , Nininger published the first edition of a pamphlet titled "A Comet Strikes the Earth", which described how Meteor Crater formed when an asteroid impacted

3010-542: The labels of tectonics, hydraulics, exfoliation, unloading (release), and cooling. Different authors have proposed contradictory hypotheses for the same joint sets and types. And, joints in the same outcrop may form at different times under varied circumstances. Tectonic joints are joints formed when the relative displacement of the joint walls is normal to its plane as the result of brittle deformation of bedrock in response to regional or local tectonic deformation of bedrock. Such joints form when directed tectonic stress causes

3080-537: The late 19th century. The canyon also crosses the strewn field , where meteorites from the crater-forming event are found. The crater was initially assumed to have been formed by a volcanic steam explosion ; evidence of geologically recent volcanic activity occurs across this part of Arizona – the southeastern edge of the San Francisco volcanic field is only about 20 mi (32 km) northwest of Meteor Crater. In 1891, mineralogist Albert E. Foote presented

3150-400: The layers immediately exterior to the rim are stacked in the reverse order to which they normally occur; the impact overturned and inverted the layers to a distance of 1–2 km outward from the crater's edge. Specifically, climbing the rim of the crater from outside, one finds: Soils around the crater are brown, slightly to moderately alkaline, gravelly or stony loam of the Winona series; on

3220-419: The local and regional geology and geomorphology but also in developing natural resources, in the safe design of structures, and in environmental protection. Joints have a profound control on weathering and erosion of bedrock. As a result, they exert a strong control on how topography and morphology of landscapes develop. Understanding the local and regional distribution, physical character, and origin of joints

3290-510: The metal he believed was buried under the crater's floor. He estimated from the size of the crater that the meteorite had a mass of 100 million tons. Iron ore of the type found at the crater was valued at the time at US$ 125/ton, so Barringer was searching for a lode he believed to be worth more than a billion 1903 dollars. "By 1928, Barringer had sunk the majority of his fortune into the crater – $ 500,000, or roughly $ 7 million in 2017 dollars." Barringer's arguments were met with skepticism. At

3360-555: The meteorites, including microscopic diamonds. His paper to the Association for the Advancement of Science provided the first geological description of Meteor Crater to a scientific community. In November 1891, Grove Karl Gilbert , chief geologist for the U.S. Geological Survey , investigated the crater and concluded that it was the result of a volcanic steam explosion . Gilbert assumed that, if it were an impact crater, then

3430-426: The minimum principal stress (the direction in which the rock is being stretched). If the tensile stress exceeds the magnitude of the least principal compressive stress the rock will fail in a brittle manner and these cracks propagate in a process called hydraulic fracturing . Hydraulic joints occur as both nonsystematic and systematic joints, including orthogonal and conjugate joint sets. In some cases, joint sets can be

3500-457: The minimum principal stress (the direction in which the rock is being stretched). This leads to the development of a single sub-parallel joint set. Continued deformation may lead to development of one or more additional joint sets. The presence of the first set strongly affects the stress orientation in the rock layer, often causing subsequent sets to form at a high angle, often 90°, to the first set. Joints are classified by their geometry or by

3570-764: The moon, and correctly interpreted them in 1892 as ejecta from a giant impact. Gilbert was one of the more influential early American geologists. He won the Wollaston Medal from the Geological Society of London in 1900. He was elected as a member to the American Philosophical Society in 1902. He was awarded the Charles P. Daly Medal by the American Geographical Society in 1910. Gilbert

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3640-455: The most well-consolidated, lithified, and highly competent rocks, such as sandstone , limestone , quartzite , and granite . Joints may be open fractures or filled by various materials. Joints infilled by precipitated minerals are called veins and joints filled by solidified magma are called dikes . Joints arise from brittle fracture of a rock or layer due to tensile stress . This stress may be imposed from outside; for example, by

3710-556: The north rim of the crater. It features interactive exhibits and displays about meteorites and asteroids , space , the Solar System , and comets including the American Astronaut Wall of Fame and such artifacts on display as an Apollo boilerplate command module (BP-29), a 1,406 lb (638 kg) meteorite found in the area, and meteorite specimens from Meteor Crater that can be touched. Formerly known as

3780-418: The order of centimeters, meters, tens of meters, or even hundreds of meters. As a result, they occur as families of joints that form recognizable joint sets. Typically, exposures or outcrops within a given area or region of study contains two or more sets of systematic joints, each with its own distinctive properties such as orientation and spacing, that intersect to form well-defined joint systems. Based upon

3850-628: The processes that formed them. The geometry of joints refers to the orientation of joints as either plotted on stereonets and rose-diagrams or observed in rock exposures. In terms of geometry, three major types of joints, nonsystematic joints, systematic joints, and columnar jointing are recognized. Nonsystematic joints are joints that are so irregular in form, spacing, and orientation that they cannot be readily grouped into distinctive, through-going joint sets. Systematic joints are planar, parallel, joints that can be traced for some distance, and occur at regularly, evenly spaced distances on

3920-528: The result of the perpendicular opening of a fracture due to tensile stress, but through the shearing of fractures that causes lateral movement of the faces. Shear fractures can be confused with joints because the lateral offset of the fracture faces is not visible in the outcrop or in a specimen. Because of the absence of diagnostic ornamentation or the lack of any discernible movement or offset, they can be indistinguishable from joints. Such fractures occur in planar parallel sets at an angle of 60 degrees and can be of

3990-415: The same size and scale as joints. As a result, some "conjugate joint sets" might actually be shear fractures. Shear fractures are distinguished from joints by the presence of slickensides , the products of shearing movement parallel to the fracture surface. The slickensides are fine-scale, delicate ridge-in-groove lineations on the surface of fracture surfaces. Joints are important not only in understanding

4060-412: The sides of a tabular igneous, typically basaltic, intrusion. They exhibit a pattern of joints that join together at triple junctions either at or about 120° angles. They split a rock body into long, prisms or columns that are typically hexagonal, although 3-, 4-, 5- and 7-sided columns are relatively common. They form as a result of a cooling front that moves from some surface, either the exposed surface of

4130-571: The site broke away from the main body before and during the impact. Shoemaker published his conclusions in his 1974 book, the Guidebook to the geology of Meteor Crater, Arizona. Geologists used the nuclear detonation that created the Sedan crater , and other such craters from the era of atmospheric nuclear testing , to establish upper and lower limits on the kinetic energy of the meteor impactor. The impact created an inverted stratigraphy , so that

4200-402: The stretching of layers, the rise of pore fluid pressure , or shrinkage caused by the cooling or desiccation of a rock body or layer whose outside boundaries remained fixed. When tensional stresses stretch a body or layer of rock such that its tensile strength is exceeded, it breaks. When this happens the rock fractures in a plane parallel to the maximum principal stress and perpendicular to

4270-439: The surface (plane) of the fracture ("Mode 1" Fracture). Although joints can occur singly, they most frequently appear as joint sets and systems. A joint set is a family of parallel, evenly spaced joints that can be identified through mapping and analysis of their orientations, spacing, and physical properties. A joint system consists of two or more intersecting joint sets. The distinction between joints and faults hinges on

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4340-501: The surface (plane) of the fracture that remains "invisible" at the scale of observation. Joints are among the most universal geologic structures, found in almost every exposure of rock. They vary greatly in appearance, dimensions, and arrangement, and occur in quite different tectonic environments. Often, the specific origin of the stresses that created certain joints and associated joint sets can be quite ambiguous, unclear, and sometimes controversial. The most prominent joints occur in

4410-465: The tensile strength of bedrock to be exceeded as the result of the stretching of rock layers under conditions of elevated pore fluid pressure and directed tectonic stress. Tectonic joints often reflect local tectonic stresses associated with local folding and faulting. Tectonic joints occur as both nonsystematic and systematic joints, including orthogonal and conjugate joint sets. Hydraulic joints are formed when pore fluid pressure becomes elevated as

4480-404: The tensile strength of the bedrock and results in jointing. In the case of unloading joints, compressive stress is released either along preexisting structural elements (such as cleavage) or perpendicular to the former direction of tectonic compression. Cooling joints are columnar joints that result from the cooling of either lava from the exposed surface of a lava lake or flood basalt flow or

4550-424: The terms visible or measurable, a difference that depends on the scale of observation. Faults differ from joints in that they exhibit visible or measurable lateral movement between the opposite surfaces of the fracture ("Mode 2" and "Mode 3" Fractures). Thus a joint may be created by either strict movement of a rock layer or body perpendicular to the fracture or by varying degrees of lateral displacement parallel to

4620-459: The time, the craters visible on the Moon were thought to be volcanic , and no impact craters were known. He persisted and sought to bolster his theory by locating the remains of the meteorite. At the time of discovery, the surrounding plains were covered with about 30 tons of large, oxidized iron meteorite fragments. This led Barringer to believe that the bulk of the impactor could still be found under

4690-409: The volume of the crater, as well as meteoritic material, should still be present in the crater's rim. Gilbert also assumed a large portion of the meteorite should be buried in the crater and that this should generate a large magnetic anomaly. Gilbert's calculations showed that the volume of the crater and the debris on the rim were roughly equivalent, which meant that the mass of the hypothetical impactor

4760-424: Was missing. There were also no detectable magnetic anomalies; he argued that the meteorite fragments found on the rim were coincidental or placed there. Gilbert publicized his conclusions in a series of lectures. In 1892, Gilbert would be among the first scientists to propose that the Moon's craters were caused by impact rather than volcanism. In 1903, mining engineer and businessman Daniel M. Barringer suggested that

4830-409: Was one of the first people to suggest that the crater was produced by a meteorite impact, with the Barringer family filing mining claims and purchasing it and its surroundings in the early 20th century. This led to the crater also being known as "Barringer Crater." Meteorites from the area are called Canyon Diablo meteorites, after Canyon Diablo, Arizona , which was the closest community to the crater in

4900-484: Was well-esteemed by all American geologists during his lifetime, and he is the only geologist to ever be elected twice as President of the Geological Society of America (1892 and 1909). Because of Gilbert's prescient insights into planetary geology, the Geological Society of America created the G.K. Gilbert Award for planetary geology in 1983. Gilbert's wide-ranging scientific ideas were so profound that

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