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A comprehensive analysis of the turbulence structure of relatively deep midlatitude katabatic flows (with jet maxima between 20 and 50 m) developing over a gentle (1°) mesoscale slope with a long fetch upstream of the Meteor Crater in Arizona is presented. The turbulence structure of flow below the katabatic jet maximum shows many similarities with the turbulence structure of shallower katabatic flows, with decreasing turbulence fluxes with height and almost constant turbulent Prandtl number. Still stark differences occur above the jet maximum where turbulence is suppressed by strong stability, is anisotropic and there is a large sub‐mesoscale contribution to the flux. Detecting the stable boundary‐layer top depends on the method used (flux‐ vs. anisotropy‐profiles) but both methods are highly correlated. The top of the stable boundary layer, however, mostly deviates from the jet maximum height or the top of the near‐surface inversion. The flat‐terrain formulations for the boundary‐layer height correlate well with the detected top of the stable boundary layer if the near‐surface and not the background stratification is used in their formulations; however, they mostly largely overestimate this boundary‐layer height. The difference from flat‐terrain boundary layers is also shown through the dependence of size of the dominant eddy with height. In katabatic flows the eddy size is semi‐constant with height throughout the stable boundary‐layer depth, whereas in flat terrain, eddy size varies significantly with height. Flux‐gradient and flux‐variance relationships show that turbulence data from different stable boundary‐layer scaling regimes collapse on top of each other showing that the dominant dependence is not on the scaling regime but on the local stability. [ABSTRACT FROM AUTHOR]

The nearly circular Meteor Crater, Arizona, is located on an extensive, slightly sloping plain, above which a south-westerly katabatic flow forms during undisturbed, clear-sky nights. For the katabatic flow over the upstream crater rim, the resulting flow regime in the lee depends on the upstream wind speed. For a shallow katabatic flow with a wind-speed maximum of about 5 m s - 1 or less at a height of about 20 m above the ground, the flow decelerates as it approaches the crater. Cold-air intrusions form, that is, cold air spills over the crater rim and runs down the inner south-west sidewall. For a deep katabatic flow with a wind-speed maximum located above the 50-m high measurement tower and comparatively higher wind speeds, the flow accelerates towards the crater. The flow separates in the immediate lee of the crater rim, forming a wake over the south-west crater sidewall. The wake can either be small, affecting only the upper part of the sidewall, or large, affecting the entire crater sidewall or even the crater floor. When flow separation occurs, the wake region over the crater sidewall is characterized by low wind speeds and potentially a return circulation near the surface. Particularly for large wakes, stability in the crater atmosphere is reduced and relatively high wind speeds occur at the crater floor, which is otherwise submerged in a strong surface-based inversion. Turbulent kinetic energy at the crater sidewall is typically higher during cold-air intrusions than is the case during flow separation, but high values can occur at the floor when a large wake forms. [ABSTRACT FROM AUTHOR]

Wolfe Creek crater lies in northwestern Australia at the edge of the Great Sandy Desert. Together with Meteor Crater, it is one of the two largest craters on Earth from which meteorite fragments have been recovered. The age of the impact is poorly constrained and unpublished data places the event at about 300,000 years ago. In comparison, Meteor Crater is well constrained by exposure dating. In this paper, we present new ages for Wolfe Creek Crater from exposure dating using the cosmogenic nuclides 10Be and 26Al, together with optically stimulated luminescence ages (OSL) on sand from a site created by the impact. We also present a new topographic survey of the crater using photogrammetry. The exposure ages range from ~86 to 128 ka. The OSL ages indicate that the age of the impact is most likely to be ~120 ka with a maximum age of 137 ka. Considering the geomorphic setting, the most likely age of the crater is 120 ± 9 ka. Last, we review the age of Meteor Crater in Arizona. Changes in production rates and scaling factors since the original dating work revise the impact age to 61.1 ± 4.8 ka, or ~20% older than previously reported. [ABSTRACT FROM AUTHOR]

In the history of the study of Meteor Crater, there is an interlude between its initial geologic exploration in early 1890s (finalized by the seminal publication of the volcanic model by Gilbert in 1896) and the spectacular research-prospective activity of Barringer, completed with a meteoritic concept published in 1905. Here it is shown that the period between 1896 and 1905 did not represent a conceptual stasis in solving the mystery of the Arizona crater. Popular interest in the attractive theme was promoted by known scientists, such as Crookes, Holder, and Meyer. However, it was primarily exemplified by the work of Joseph A. Munk. In unnoticed publications from 1903 to 1906, he presented Coon Mountain indubitably as a meteorite crater, along with a proposal to adopt the appropriate name of Meteorite Mountain for this natural curiosity. His proimpact geologic arguments were widely repeated in later papers. In addition, Munk was a visionary pioneer in the propagation of the geotourist attraction represented by this geologic wonder, as manifested in his well-read guidebook Arizona Sketches. Furthermore, a surprising but significant issue is the hidden stimulating role of Fred W. Volz, known hitherto as a local businessmen and meteorite dealer. Especially in the light of Munk's publications, Volz is shown to have been an insightful observer of geologic phenomena, including a progressive revival of Gilbert's incipient conception of a buried "stellar body" under Coon Mountain (rejected by Gilbert himself). Even if this activity can be downgraded as only popular writing, Munk and (to some degree) Volz ought to be known at least as inspiring propagators and therefore pioneers of the meteorite hypothesis regarding Meteor Crater, independently of the widely known Barringer engagement. [ABSTRACT FROM AUTHOR]

We have generated sub-millimetre-resolution DEMs of weathered rock surfaces using SfM photogrammetry techniques. We apply a close-range method based on structure-from-motion (SfM) photogrammetry in the field and use it to generate high-resolution topographic data for weathered boulders and bedrock. The method was pilot tested on extensively weathered Triassic Moenkopi sandstone outcrops near Meteor Crater in Arizona. Images were taken in the field using a consumer-grade DSLR camera and were processed in commercially available software to build dense point clouds. The point clouds were registered to a local 3-D coordinate system (x , y , z), which was developed using a specially designed triangle-coded control target and then exported as digital elevation models (DEMs). The accuracy of the DEMs was validated under controlled experimental conditions. A number of checkpoints were used to calculate errors. We also evaluated the effects of image and camera parameters on the accuracy of our DEMs. We report a horizontal error of 0.5 mm and vertical error of 0.3 mm in our experiments. Our approach provides a low-cost method for obtaining very high-resolution topographic data on weathered rock surfaces (area < 10 m 2). The results from our case study confirm the efficacy of the method at this scale and show that the data acquisition equipment is sufficiently robust and portable. This is particularly important for field conditions in remote locations or steep terrain where portable and efficient methods are required. [ABSTRACT FROM AUTHOR]

Observations are analyzed to explain an unusual feature of the nighttime atmospheric structure inside Arizona's idealized, basin-shaped Meteor Crater. The upper 75%-80% of the crater's atmosphere, which overlies an intense surface-based inversion on the crater's floor, maintains a near-isothermal lapse rate during the entire night, even while continuing to cool. Evidence is presented to show that this near-isothermal layer is produced by cold-air intrusions that come over the crater's rim. The intrusions are driven by a regional-scale drainage flow that develops over the surrounding inclined Colorado Plateau. Cold air from the drainage flow builds up on the upwind side of the crater and splits around the crater at low levels. A shallow layer of cold air, however, spills over the 30-60-m-high rim and descends partway down the crater's upwind inner sidewall until reaching its buoyancy equilibrium level. Detrainment of cold air during its katabatic descent and compensatory rising motions in the crater atmosphere destabilize the basin atmosphere, producing the observed near-isothermal lapse rate. A conceptual model of this phenomenon is presented. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogeological modification of Meteor Crater produced a spectacular set of gullies throughout the interior wall in response to rainwater precipitation, snow melting, and possible groundwater discharge. The crater wall has an exceptionally well-developed centripetal drainage pattern consisting of individual alcoves, channels, and fans. Some of the gullies originate from the rim crest and others from the middle crater wall where a lithologic transition occurs; broad gullies occur along the crater corner radial faults. Deeply incised alcoves are well developed on the soft Coconino Sandstone exposed on the middle crater wall, beneath overlying dolomite. In general, the gully locations are along crater wall radial fractures and faults, which are favorable locales of erosion due to preferential rock breakup from faulting, and groundwater flow/discharge; these structural discontinuities are also the locales where the surface runoff from rain precipitation and snow melting can preferentially flow, causing erosion and crater degradation. Channels are well developed on the talus deposits and alluvial fans on the periphery of the crater floor. Caves exposed on the lower crater level point to percolation of surface runoff and selective discharge through fractures on the crater wall. In addition, lake sediments on the crater floor provide significant evidence of a past pluvial climate, when the water table was higher, and groundwater may have seeped from springs on the crater wall. Although these hydrological processes continue at Meteor Crater today, conditions at the crater are much more arid than they were soon after impact, reflecting a climatic shift. This climate shift and the hydrological modifications observed at Meteor Crater provide insights for landscape sculpturing on Mars during various parts of its history. [Copyright &y& Elsevier]

The individual components of the slope-parallel surface radiation balance were measured in and around Arizona’s Meteor Crater to investigate the effects of topography on the radiation balance. The crater basin has a diameter of 1.2 km and a depth of 170 m. The observations cover the crater floor, the crater rim, four sites on the inner sidewalls on an east–west transect, and two sites outside the crater. Interpretation of the role of topography on radiation differences among the sites on a representative clear day is facilitated by the unique symmetric crater topography. The shortwave radiation balance was affected by the topographic effects of terrain exposure, terrain shading, and terrain reflections, and by surface albedo variations. Terrain exposure caused a site on the steeper upper eastern sidewall of the crater to receive 6% more daily integrated shortwave energy than a site on the lower part of the same slope. Terrain shading had a larger effect on the lower slopes than on the upper slopes. At the lower western slope site the daily total was reduced by 6%. Measurements indicate a diffuse radiation enhancement due to sidewall reflections. The longwave radiation balance was affected by counterradiation from the crater sidewalls and by reduced emissions due to the formation of a nighttime temperature inversion. The total nighttime longwave energy loss at the crater floor was 72% of the loss observed at the crater rim. [ABSTRACT FROM AUTHOR]

Observations from a recent meteorological experiment in the Meteor Crater, a small, near circular, enclosed basin, in northern Arizona of the United States, are used to investigate the status of the atmosphere in the basin as indicated by temperature inversion and its relationship to ambient atmospheric conditions. Strong synoptic winds aloft do not necessarily imply that no inversion could develop in the basin. Instead, the near-surface wind over the plain surrounding the basin is found to be a more important factor in determining whether the basin atmosphere would be coupled to, or decoupled from, its ambient environment. A necessary condition for the decoupling and the development of a strong inversion overnight is that the mean nighttime temperature over the plain needs to be less than 5 m s−1. The low-level stability of the ambient environment also plays an important role. It was found that as long as the bulk Richardson number over the plain is less than 0.6, turbulence would exit over the plain and influence the basin atmosphere at least partially through the night, preventing a strong temperature inversion from developing in the basin. The strength of the inversion in the basin appears to be increase exponentially with the longwave radiation loss from the upper basin sidewalls. Over the basin floor, the relation between inversion strength and longwave radiation loss is poor mainly because the cooling of air over the basin floor is a combination of radiative cooling and the drainage of cold air from the sidewalls. [ABSTRACT FROM AUTHOR]

The article provides information on the meteorological field experiment which is called Meteor Crater Experiment (METCRAX 2006) conducted in Meteor Crater near Winslow, Arizona. One of the objectives of METCRAX is to study the microscale structure and evolution of the stable boundary layer in and around the crater. It also determine whether an analog to lake and ocean seiches occurs in the crater atmosphere. An overview of the description of the meteor crater, the METCRAX field experiment design, and the measurements and instruments used in the study is also presented.

The article offers information on various craters which were effected by the occurrences of meteorites. It states that the meteor crater in Arizona, which at 50,000 years old is nicely preserved in the desert climate, was one of the earliest craters to have its impact origin recognized. Another crater is the 10-kilometer-wide Bosumtwi which contains Ghana's only natural lake. Other craters which were identified on the planet Mars are also mentioned. Photographs of these craters of varying dimensions were also supplied.

Meteorite impact structures are found on all planetary bodies in the Solar System with a solid surface. On many planets, impact craters are the dominant landform. Earth's active geology, however, tends to rapidly erase impact structures from the geological record, although we know currently of 174 confirmed impact sites. Impact events are destructive and have been linked to at least one of the ‘big five’ mass extinctions over the past 540 Ma. But they also provide certain economic benefits, including the formation of metalliferous ore deposits and hydrocarbon reservoirs. Impact structures can also form new biological niches, which can provide favourable conditions for the survival and evolution of life. Despite this, it was only in the past 40 years that the importance of impact cratering as a geological process was recognized and only during the past 15–20 years that the study of meteorite impact structures has moved into the geological mainstream. There is, therefore, still considerable potential for new and exciting advancements. [ABSTRACT FROM AUTHOR]

The first scientific studies of Barringer crater, Arizona, USA (also known as the Coon Butte crater), began more than a century ago; however, views on the crater’s origin have been contradictory. At the beginning of the 20th century, D.M. Barringer, a mining engineer, became interested in the possibility of finding large useable iron masses in this crater and searched for these masses for more than 25 years, standing up for the idea of the crater’s meteoric origin, contrary to the objections of opponents who tried to indicate that the crater was caused by terrestrial geological processes. Mining, accompanied by different scientific works, made it possible to obtain reliable data on the structure and impact origin of the crater; however, attempts to find meteorite iron deposits in this crater were unsuccessful. Barringer crater was the first object on the Earth where purposeful studies were performed for many decades and made it possible to develop many criteria of the impact origin of circular geological structures and mechanisms of formation of these structures, as well as to compare this crater with similar morphostructures on the surfaces of other planets. These studies have played an important role in the formation and development of the theory of impact cratering, which has been generally acknowledged in present-day science. [ABSTRACT FROM AUTHOR]

Abstract: This study examines the effects of natural shock metamorphism on fluid inclusions trapped in porous sedimentary target rocks and compares these results to previous experimental work on single crystal quartz. Samples of shock metamorphosed Coconino sandstone were collected from Barringer Meteorite Crater (Meteor Crater, Arizona) and classified based on their shock features into the six shock stages described by Kieffer [S.W. Kieffer, 1971. Shock metamorphism of the Coconino sandstone at Meteor Crater, Arizona, Journal of Geophysical Research 76, 5449-5473.]. The frequency of two-phase fluid inclusions decreases dramatically from unshocked samples of Coconino sandstone through shock stages 1a, 1b, and 2. No two-phase fluid inclusions were observed in shock stage 3 or 4 samples. However, the total number of grains containing fluid inclusions remains approximately the same for shock stages 1a–2, suggesting that two-phase fluid inclusions reequilibrated during impact to form single-phase inclusions. In shock stages 3 and 4, the total number of inclusions also decreases, indicating that at these higher shock pressures fluid inclusions are destroyed by plastic deformation and phase changes within the host mineral. Entrained quartz grains within a shock stage 5 sample contain two-phase inclusions, emphasizing the short duration of melting associated with the impact and the heterogeneous nature of impact processes. These results are similar to those observed in single-crystal experiments, although inclusions survive to slightly higher shock pressures in samples of naturally shocked Coconino sandstone. Results of this study suggest that the rarity of fluid inclusions in meteorites does not preclude the presence of fluids on meteorite parent bodies. Instead, fluid inclusions trapped during alteration events may have been destroyed due to shock processing. In addition, loss of fluids from inclusion vesicles along fractures and microcracks may lead to shock devolatilization, even in unsaturated target rocks. [Copyright &y& Elsevier]

The article discusses a report by researcher Jourdan and colleagues regarding age-dating of craters. There are 174 characterized impact structures on Earth ranging in size and age from South Africa to Arizona in the U.S. Topics include how understanding their age-size relationship could aid in the assessment of the impact and its relation to events such as extinctions. A brief overview of the difficulties in aging craters is presented.

Mentions Internet related news pertaining to science. The University of Arizona, Tucson's Tree of Life Website; Irish teenager, Sarah Flannery, who has developed a cryptography scheme for encoding Internet messages; National Resources Canada's database that lists impact craters on Earth; More.