Huge Crater Research Articles

A comparative Study of the Erosive Wear Caused by Organic and Inorganic Abrasive Particles

In this study, erosion tests were conducted to evaluate the abrasivity of organic particles to produce wear on a material surface with higher hardness. The novelty of this research work was that pistachio shells, which are usually waste that ends up in the garbage, were collected, ground and sieved to obtain a sufficient quantity of pistachio angular particles to be used productively to perform these wear tests. Additionally, sea shells were thought of as an alternative to organic abrasives, and these were ground, sieved and prepared to be able to carry out the testing. The erosion tests conducted based on ASTM G76 and SEM images showed typical wear mechanisms such as high plastic deformation (material displacement) characterized by micro-cutting and micro-ploughing actions, grooves with lifted lips in the edges as pistachio grits employed to run the tests. On the other hand, a conventional abrasive as glass bead particles caused huge craters, broken and smeared flakes, ploughing and circumferential cracks on the AISI 420 stainless steel surfaces. The highest erosion rates were reached as glass beads were employed to run the erosion tests. AFM technique was used to show the surface variations after the erosive impacts. The eroded scars produced by pistachio and sea shells allowed us to remark that the proposed organic abrasives could be used for polishing, surface finishing and cleaning applications on surfaces of mechanical elements that are dirty or rusty. This was due to their low density, which led to low and very superficial erosion damage.

Potholes Detection in Doppler Radar Signal’s Power Spectral Density using Decision Tree

Potholes are defects on the surface of roads, streets, or pavements brought on by depressions or holes, which are hazardous for vehicles and pedestrians, whether small divots or huge craters. Various methods have been explored to improve the accuracy of potholes detection. Existing approaches have advantages and disadvantages. This paper presents the proposed method of pothole detection utilising Doppler Radar signal's Power Spectrum Density (PSD) together with the Decision Tree classification algorithm. While continuous waveform (CW) radar is able to identify moving targets, it cannot localise the exact depth of the reflector, which is the prominent characteristic of potholes. In addition, the target's reflected signal is likely to be masked by nearby harmonics. Since the radar is moving despite the target of interest, mounting it on a moving vehicle offers a different perspective. This paper explores the potential of Doppler radar's signal for pothole detection while comparing two Machine Learning (ML) techniques. A commercially over-the-shelf (COTS) K-LC2 Doppler radar was employed to acquire pothole and non-pothole raw datasets. Doppler signal was hardly distinguished between pothole and non-pothole, either in the time or frequency domain. Hence, Doppler signals were converted to power spectral density (PSD), and PSD's features were extracted. Extracted features were applied with the coarse Decision Tree (DT) and K-Nearest Neighbours (KNN) classification algorithms. The result exhibits a better accuracy of 91.2% for 80:20 distribution by using the Decision Tree.

A new prospect to analyse the spectral properties of v-type asteroids

Among main belt asteroids, some have a spectrum similar to Vesta so they are taxonomically classified as V-type asteroids. Probably they were removed from Vesta and migrated to their current positions via some still unknown dynamical mechanisms. Several issues on the relationship between V-type asteroids, Howardite-Eucrite-Diogenite (HED) meteorites and Vesta are still unresolved. Although some of them can be directly linked to (4) Vesta, forming its dynamical family, others do not appear to have a clear dynamical link, thus suggesting the existence of other basaltic parent bodies. In this work we present a new approach of analysis to investigate 76 VNIR V-type asteroids spectra downloaded from PDS. The composition of the regolith and particle size of V-type asteroid have been investigated with a combination of spectroscopic analysis and Hapke radiative transfer model. Retrieved particle sizes are very small, with a mean value of 20 μm.Therefore, we look for statistically significant differences among the modal mineralogy of V-type asteroids belonging to different dynamical subclasses. It seems there is a possible chronologic link between impact events on Vesta and the V-type families. The most ancient V-type family, e.g. Low-I asteroids, seems to have a eucritic composition compatible with an ejection of the outermost layer of Vesta. The Fugitive V-type were probably ejected in an older cratering event that produced the Veneneia basin while the Vestoids family, whose dynamical parameters are still more similar to Vesta and which seems to be the youngest family among them, could be associated to Rheasilvia basin. The last two families seem to have a diogenitic composition compatible with that of the south of Vesta, where the two huge craters are located.Spartacus asteroid is also analysed and it was found to have a modal mineralogy consistent with the presence of olivine as noted before (Moskovitz et al.,2010; Burbine et al., 2001).

Potential Analysis of Ex-Coal Mining Land As Pumped Storage Hydro Powerplant In Kutai Kartanegara, East Kalimantan

The growth of electricity demand will increase 56.8% in 10 years. Meanwhile, the fulfillment of electricity in Indonesia is dominated by coal. The amount of electricity growth has not balanced yet by the amount of electricity supply. It causes the electricity deficit in some areas, especially at the peak load period. One of the areas that often have electrical power deficit is East Kalimantan, although the province is one of the biggest coal mining areas in Indonesia. The mining activities give several impacts in environmental damages especially in the ex-coal mining land which has not been well managed. The impact includes an irreversible change of landscape and huge craters caused by open mining activities. In this study, an analysis is conducted for utilization of ex-coal mining land in Kutai Kartanegara as a reservoir of energy storage system type Pumped Hydroelectric Storage (PSH). The analysis provides a comparison of three variations of the piping line system. The study uses the spatial data in the form of Digital Elevation Model (DEM) to calculate the time of starting operation system, expected generated energy, required energy for power plant operation and the efficiency of the system. This study compares some criteria based on three variations of the piping line system and the effect on the efficiency of the system.

The Meetings of Disaster Victims as a Space for Developing Community Resilience

The objective of this study is to analyze how the collective meetings held in Mãe Luiza community have helped in increasing community resilience after a disaster. This is a case study related to the disaster in Mãe Luiza community due to the heavy rains that hit the city of Natal in June 2014. The disaster was a landslide that culminated in a huge crater affecting around 200 families. The method was based on the community ergonomics framework. The meetings realized by community members after the disaster were followed and mediated by ergonomists to understand how the community deal with disaster management issues. It was found that the meetings become an important space for the disaster victims helping then for different purposes, such as: to get information about the real situation that they were; in clarify conflicting information; obtain guidance; identify and organize their real demands; discuss and decide on the strategies to be adopted; bring government officials and technicians to the community to clarify, discuss and resolve their; involve community leaders; schedule a public hearing in the municipal parliament; be represented in front of authorities and the media; establish alliances with sectors of society; experience the collective participation, reflect and learn from their own experiences, and; monitor the decisions and actions taken by the authorities. We conclude from these results that the involvement and participation of the residents affected by the disaster in the meetings, following the decisions that needed to be taken in response to the disaster contributes to increasing the community resilience, as well as contribute to the development skills and to improve the interaction among individuals from the community.

Nanosecond pulsed laser ablation of brass in a dry and liquid-confined environment

The effect of ambient environment (dry or wet) and overlapping laser pulses on the laser ablation performance of brass has been investigated. For this purpose, a Q-switched, frequency doubled Nd:YAG laser with a wavelength of 532 nm, pulse energy of 150 mJ, pulse width of 6 ns and repetition rate of 10 Hz is employed. In order to explore the effect of ambient environments, brass targets have been exposed in deionized water, methanol and air. The targets are exposed for 1000, 2000, 3000 and 4000 succeeding pulses in each atmosphere. The surface morphology and chemical composition of ablated targets have been characterized by using Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and Attenuated Total Reflection (ATR) techniques. In case of liquid environment, various features like nano- and micro-scale laser-induced periodic surface structures with periodicity 500 nm–1 μm, cavities of size few micrometers with multiple ablative layers and phenomenon of thermal stress cracking are observed. These features are originated by various chemical and thermal phenomena induced by laser heating at the liquid–solid interfaces. The convective bubble motion, explosive boiling, pressure gradients, cluster and colloid formation due to confinement effects of liquids are possible cause for such kind of features. The metal oxides and alcohol formed on irradiated surface are also playing the significant role for the formation of these kinds of structure. In case of air one huge crater is formed along with the redeposition of sputtered material and is ascribed to laser-induced evaporation and oxide formation.

Essay Review: Sidereus Nuncius Debated, Galileo's O., Galileo's Sidereus Nuncius: A Comparison of the Proof Copy (New York) with other Paradigmatic Copies, Galileo Makes a Book: The First Edition of the Sidereus Nuncius, Venice 1610

SIDEREUS NUNCIUS DEBATED Galileo 's O. Edited by Horst Bredekamp. Vol. i: Galileo 's Sidereus Nuncius: A Comparison of the Proof Copy (New York) with Other Paradigmatic Copies. Edited by Irene Briickle and Oliver Hahn. Vol. ii: Galileo Makes a Book: The First Edition of the Sidereus Nuncius, Venice 1610. Paul Needham (Akademie Verlag, Berlin, 2011). Pp. 188 + 249. euro128. ISBN 978-3-05-005095-9.The discovery in 2005 of a copy of Galileo's Sidereus nuncius (1610) containing wash drawings instead of the usual etchings has garnered attention out of proportion to its historical significance. That is owing partly to commercial interest and partly to scholarly compulsion. The elaborate books under review contain the latest contributions to the printing history of Galileo's masterpiece and the provenance of the odd copy.In Galileo 's Sidereus nuncius, Horst Bredekamp and a team of experts support his earlier findings that the odd copy (labelled after the initials of its owners) is a bound proof documenting a stage in the printing and that its washes guided the etcher. Bredekamp's further judgements, based on his expertise in Galileo's style of drawing, that the author himself did the washes and, perhaps, also the etchings, while not confirmed, remain alive.The ML illustrations are in general closer to the etchings than to either of the other two sets of drawings previously considered as the etchings' antecedents. These are the figures in a letter to an unknown correspondent dated 7 1610 (JL for January letter) and on the familiar bifolium preserved among Galileo's papers in (FB for Florence bifolium). FB has no date; JL is known from two seventeenth-century copies, one now lost, of a lost original. JL's date and illustrations, which include depictions of the progressive illumination of a huge crater that appears combined with other views on the etchings, suggest the chronological sequence JL, ML, etchings. That leaves the bistre washes of FB, whose single crater stands apart in a miniature all to itself, disconnected from the printing history of Sidereus nuncius. This conclusion, which Bredekamp reached in his Galilei der Kunstler (2007), is reinforced by Paul Needham's Galileo makes a book.Needham gives a masterful account of the composition, make-up, ingrethents, and printing of Sidereus nuncius (SN). His apt diagrams guide the reader through details about signatures, additions, subtractions, watermarks, layouts, papers, presses, and printing. One learns why and when Galileo decided to impose his out-of-scale crater on a terminator where he probably had not seen it. It was to save space. The original design of SN had called for seven depictions of the Moon's surface for which only five spaces could be found after Galileo added sections concerning the Moon's silhouette and the height of lunar mountains, perhaps in order to pre-empt objections that had occurred to him when reviewing his draft.1Needham was able to put together so intricate an account because the original draft of SN, with its corrections and expansions, has survived. So have a fair copy of about half of it and a good many of the 550 standard copies of the book originally printed. Add to these the dated letters Galileo wrote while seeing it through the press and inferences from watermarks, and the relevant documentation dwarfs that available for all of Shakespeare's plays. Needham remarks that no other early printed book except Gutenberg's bible lends itself to, or has received, the elaborate analysis he has given Sidereus nuncius.Several astronomers previously sought to identify the dates and even hours when Galileo made the observations apparently recorded on FB. The rapidly changing inventory of features visible near the terminator makes this exercise practicable and its results probable. If, however, FB does not belong in the pre-printing sequence but, as Bredekamp suggests, to preparations for the second edition of Sidereus nuncius that Galileo advertised but did not issue, the identifications rest on a false assumption. …

Motion of blocks on the surface of Phobos: New constraints for the formation of grooves

Although grooves are common on asteroids, on Phobos the grooves have been the subject of various formation hypotheses for two reasons: the fact that Phobos is orbiting around Mars close to the Roche limit, implies an unusual gravity environment as well as the presence of the huge crater impact, Stickney, which seems to be related at least to a family of grooves. Among many hypotheses, it has been suggested that the grooves could have been dug by rolling Stickney ejecta, but this hypothesis was questioned using two main arguments: no block was observed at the end of the grooves, nor do they run downslope. Thus, the study of surface and near surface dynamics on Phobos can clarify the soundness of these controversial arguments.The present study explores this idea by computing the trajectory of a test mass gliding on the surface of Phobos for any initial position and velocity. An ellipsoidal model of Phobos is used for both the gravity and surface geometry, and several orbiting distances from Mars are considered. It is shown that, due to the Phobos rotation, the trajectories generally do not run downslope even for velocities as low as ∼1m/s. In consequence the corresponding argument against the rolling blocks hypothesis is not applicable. This hypothesis, however, is clearly ruled out for the sets of parallel grooves in the polar regions because of the curvature of the computed trajectories. On the contrary the trajectories issued from the rim of Stickney close to the equator, with velocities of a few m/s, show similitude with the corresponding groove patterns, in particular for the east–west asymmetry. In some conditions the trajectories leave the surface, which may account for regions free of grooves and for trails without blocks at the end. Consequently, the rolling block hypothesis cannot be rejected outright until further analysis is carried out. Damping of the motion on the regolith is simulated introducing a solid damping coefficient in the equations. A relatively small but not unrealistic coefficient of ∼0.1 accounts for the length of the long main western hypothetic block trails. The simulations with damping confirm that the trajectories turn downslope only at the very end for velocities ⪡1m/s, but valuable comparison with the observations requires a better model.

An Early Big Hit to Mars May Have Scarred the Planet for Life

PLANETARY GEOLOGY Earth has its high-standing continents and low-lying ocean basins, thanks to plate tectonics. And Mars has its smooth northern lowlands and its cratered highlands. But there's no credible sign that plate tectonics ever operated on Mars, so how did a third of the planet come to be as much as 4 kilometers lower than the rest? For the past quarter-century, a leading theory has held that a giant impact battered the young planet and excavated the northern lowlands, but that idea seemed to have serious problems. Now, two new studies purport to ease the difficulties with a giant impact. In one study, researchers reveal the true dimensions of the huge “Borealis basin,” making it look much more like the crater of a giant impact. And a second group has run simulations that suggest how an impactor could have blasted out an 8000-kilometer-wide crater without melting it into an unrecognizable puddle of magma. “I think there's much to recommend [a giant impact] now with all this new work,” says Sean Solomon, a planetary geophysicist at the Carnegie Institution of Washington's Department of Terrestrial Magnetism in Washington, D.C. ![Figure][1] Striptease. Removing the Tharsis volcanoes of Mars (reds and yellows, left panel) from part of the northern lowlands (light blue, right panel, top ) uncovered an elliptical basin that looks like an impact crater. CREDIT: MARS ORBITER LASER ALTIMETER (MOLA) TEAM/GODDARD SPACE FLIGHT CENTER/NASA Last month, planetary geophysicist Jeffrey Andrews-Hanna of the Massachusetts Institute of Technology in Cambridge and colleagues presented their test of the giant-impact hypothesis at the Lunar and Planetary Science Conference (LPSC) in Houston, Texas. In 1984, planetary scientists Donald Wilhelms, now retired from the U.S. Geological Survey, and Steven Squyres of Cornell University first proposed that a huge impactor had blasted out the Borealis basin. Fitting a circle to the “dichotomy boundary” between the basin and the highlands, they suggested that the circle could mark the outer edge of a huge crater. But the fit was too rough to win many converts. So Andrews-Hanna and his colleagues looked for a better way to trace out the dichotomy boundary. The great Tharsis volcanic complex had obscured much of the boundary when it smothered one-quarter of the planet with lava hundreds of millions of years after the lowlands formed. To “remove” Tharsis, they drew on measurements of martian gravity and surface height from the past decade of Mars orbiters. Subtle variations in the pull of gravity—evidenced in variations of a spacecraft's orbit—reflect the added mass of Tharsis lavas as well as the extent of the deep, less-dense crustal rock buoying up the highlands. The height of the surface constrains the volume of added lavas. By combining the data in a model, the researchers erased Tharsis's contribution to the present surface and traced the topographic edge of the Borealis basin right under Tharsis. Rather than a circle, the best shape for the basin turns out to be a 10,650-kilometer-long ellipse, they reported at the LPSC meeting. That's a familiar look for big impact basins. The 2300-kilometer Hellas impact basin in the southern highlands, for example, is also elliptical and also underlain by a uniformly thin crust. And there's no particular reason, Andrews-Hanna said, why the giant-impact theory's only serious rival—a peculiar sort of churning deep within the planet—would produce an elliptical basin or the observed sharp boundary between thin and thick crust. The other long-standing objection to impact excavation was the mere survival of a craterlike feature of any sort. Any object hundreds of kilometers across that hit Mars at tens of thousands of kilometers per hour, the thinking went, would heat the planet so dramatically that any crater would disappear in a sea of globe-girdling melted rock. Now that computer models are up to the task of simulating giant impacts in detail, that thinking is changing. As most recently reported at last December's American Geophysical Union meeting, planetary scientist Margarita Marinova of the California Institute of Technology in Pasadena and colleagues have simulated a range of giant impacts on Mars, all producing 8000-kilometer craters. They found that the melt from vertical impacts does in fact obliterate the crater but that faster, low-angle impacts do not. Simulated glancing blows at angles below 30° produce less melt overall and splash much of it into space. The giant-impact mechanism “was always thought dynamically impossible,” said Andrews-Hanna at LPSC. “Now you can't dismiss the possibility.” The two studies are convincing researchers that “the giant impact lives (after all)!” as planetary geophysicist Roger Phillips of Southwest Research Institute in Boulder, Colorado, playfully writes in an e-mail. Few are entirely won over yet, but a giant impact worked out as the origin of Earth's moon. Perhaps it will also serve to explain the deepest mystery of martian geology. [1]: pending:yes

Earth after the Moon-forming impact

The Hadean Earth is widely and enduringly pictured as a world of exuberant volcanism, exploding meteors, huge craters, infernal heat, and billowing sulfurous steams; i.e., a world of fire and brimstone punctuated with blows to the head. In the background the Moon looms gigantic in the sky. The popular image has given it a name that celebrates our mythic roots. A hot early Earth is an inevitable consequence of accretion. The Moon-forming impact ensured that Earth as we know it emerged from a fog of silicate vapor. The impact separated the volatiles from the silicates. It took approx. 100 years to condense and rain out the bulk of the vaporized silicates, although relatively volatile elements may have remained present in the atmosphere throughout the magma ocena stage. The magma ocean lasted approx. 2 Myr, its lifetime prolonged by tidal heating and thermal blanketing by a thick CO2-rich steam atmosphere. Water oceans condensed quickly after the mantle solidified, but for some 10-100 Myr the surface would have stayed warm (approx. 500 K) until the CO2 was removed into the mantle. Thereafter the faint young Sun suggests that a lifeless Earth would always have been evolving toward a bitterly cold ice world, but the cooling trend was fiequently interrupted by volcanic or impact induced thaws. A cartoon history of water, temperature, and carbon dioxide in the aftermath of the moon-formining-impact is shown. How long it stays hot depends on how long it takes to scrub the C02 out of the atmosphere.

Mass transfer in the satellite system of Neptune: implications for Triton's crater asymmetry

In this paper, we shall analyse a promising way to explain the huge crater asymmetry observed on Triton, the largest of Neptune's satellites. Triton shows, as well as many other satellites in the Solar System, a non-symmetric crater distribution on its surface. This fact is principally due to the synchronous rotation of these satellites, as shown by many theoretical works (see Shoemaker and Wolfe, Satellites of Jupiter, University of Arizona Press, Tucson, 1992, p. 277; Horedt and Neukum, Icarus 60 (1984) 710; Zahnle et al., Icarus 136 (1998) 202; Zahnle et al., Icarus 153 (2001) 111). However, on Triton the asymmetry is much more pronounced than on other satellites, and it exceeds what the models, in which the source of the craters are bodies in heliocentric orbits, can account for. For this reason, many authors (Croft et al., Icarus 99 (1992) 94; Schenk and Sobieszczyk, American Astronomical Society, DPS Meeting, Vol. 31, 1999; Zahnle et al., Icarus 153 (2001) 111) proposed that the origin for Triton's asymmetry has to be found in a swarm of bodies having planetocentric orbits, instead of heliocentric ones. Here, we analyse from a dynamical point of view the possibility that such swarm of fragments was generated by a collision between an inner satellite and a third object (a process we call ‘mass transfer’). Moreover, we discuss the possibility that the observed crater distribution on Triton comes from two populations: heliocentric bodies responsible for a few big craters, plus planetocentric bodies responsible for the big asymmetry. Finally, we discuss some implications for ground observations.

Rehabilitation of an handoned quarry used as uncontrolles landfill

It has been a common although the least rational practice for a lot of abandoned quarries to be used as sites for uncontrolled waste disposal. Such is the case of the Karens abandoned quarries in Athens. Greece. The area of Kareas. faced an intense quarrying activity during the 60s and 70s, though without any envirorniicntal consideration, thus causing the dramatic aesthetic degradation of the mountain's visible side. For the next twenty years, in the name of reshaping of the huge craters which had been created in the area, an uncontrolled disposal of constrution debris as well as municipal solid waste ( MSW) took place. Thus, the largest uncontrolled landfill in Greece was formed, stretching to almost 40 hectares, particulary in one of the most beautiftil sites of Athens As a result, new, more intense environmental problems appeared, such is landslide hazards, ground water pollution, visual pollution etc. This paper presents the overall methodology for the rehabilitation of the area, which.has proved to be a complicated scientific and technical, problem.

Spacecraft waltzes past Mathilde

On June 27 at 8:40 EDT, NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 1200 km of asteroid 253 Mathilde and snapped pictures for 25 minutes. An hour later, at the Johns Hopkins University Applied Physics Laboratory (APL), scientists were in for a few surprises as the images formed on their computer screens.First, they saw a very deep shadow caused by a 20‐km‐wide crater, which turned out to be one of Mathilde's many scars. “The degree to which the asteroid has been battered by collisions is astounding,” said Joseph Veverka of Cornell University, who leads the missions's imaging science team. “At first glance, there are more huge craters than there is asteroid.”

Earth rocked by combination punch

The Popigai impact structure is a remnant of a huge crater in Siberia, 100 km across. It was formed when a comet or asteroid hit the Earth, some time between 5 and 65 million years ago — no one could be more precise than that. But now it has been dated to about 35.5 million years ago, almost the same time as the Chesapeake Bay crater off the coast of North America. Could these two impacts together have caused the mass extinction of the late Eocene?

Excursion guide 11: Mount St Helens

The 1980 eruption of the Mount St Helens volcano produced a huge crater, massive debris flows and truly remarkable blast effects. All the features are still very visible, and the site offers easy access for an unforgettable visit.

Hazards due to comets and asteroids

In 1993, the U.S. Department of Defense declassified information dealing with frequent explosions in the upper atmosphere caused by meteoric impact. It is estimated that impacts have occurred of a magnitude equivalent to the atomic bomb detonated at Hiroshima. Not all such space voyagers meet their end in the atmosphere, however; huge craters attest to the bombardment of earth over millions of years, and a major impact may have resulted in the extinction of dinosaurs. An impact in Siberia near the beginning of this century proves that such events are not confined to geologic time. Hazards Due to Comets and Asteroids marks a significant step in the attempt to come to grips with the threats posed by such phenomena. It brings together more than one hundred scientists from around the world, who draw on observational and theoretical research to focus on the technical problems related to all aspects of dealing with these hazards: searching for and identifying hazardous comets and asteroids; describing their statistics and characteristics; intercepting and altering the orbits of dangerous objects; and applying existent technologies rocket boosters, rendezvous and soft-landing techniques, instrumentation to such missions. The book considers defensive options for diverting or disrupting an approaching body, including solar sails, kinetic-energy impacts, nuclear explosives, robotic mass drivers, and various propulsion systems. A cataclysmic impact posing a threat to life on Earth is a possibility that tomorrow's technology is capable of averting. This book examines in depth the reality of the threat and proposes practical measures that can be initiated now should we ever need to deal with it.

Spikes in condensed rare gases induced by keV-atom bombardment.

We investigate by molecular-dynamics simulation the time evolution of a collision cascade in a condensed Ar solid, initiated by a 1-keV Ar atom. The particle density and velocity in the collision-cascade volume, the kinetic- and potential-energy distributions of the recoiling Ar atoms, and the energy distribution of sputtered particles are monitored. The high pressure building up in the core of the cascade drives the material into the cascade periphery and towards the surface. The surface erupts and hundreds of atoms are emitted, leaving behind a huge crater.

Historic Natural Events

June 30, 1908. The Siberian Meteorite.—A great meteorite fell in the upper basin of the Podkamennaia Tugunska River, Siberia, about 60° N., 71° E. The place of fall, as described in 1927, had the appearance of a huge crater, several kilometres across, surrounded by an amphitheatre of mountain chains and peaks. The area, formerly forest, was completely wrecked; lines of stripped tree trunks without branches or bark lay struck to the ground in parallel rows, their tops away from the centre of fall of the meteorite. Even where the pines were standing they were usually trunkless and branchless, and showed signs of having been burnt over an area tens of kilometres across. More than a thousand reindeer were killed, some disappeared entirely, burnt remains of others were found. The burning was not due to ordinary fire, but probably to the cloud of incandescent gases which accompanied the meteorite. The force of the impact threw the ground into flat folds, but the greatest damage was done by the air wave. At a distance of nearly 400 miles the noise and vibration resembled that of a nearby explosion. The air-wave probably passed completely round the world; it was clearly shown on micro-barographs in England, where its cause was at the time unknown, and it aroused great interest. It was described as a succession of four undulations, commencing with a range of about five-thousandths of an inch, lasting about a quarter of an hour, and then violently interrupted by a sudden, though slight, explosive disturbance which set up different and much faster oscillations for a similar interval.