Terrestrial Impact Structures Provide the Only Ground Truth Against Which Computational and Experimental Results Can Be Com Pared
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3-D Seismic Characterization of a Cryptoexplosion Structure
Cryptoexplosion structure 3-D seismic characterization of a eryptoexplosion structure J. Helen Isaac and Robert R. Stewart ABSTRACT Three-quarters of a circular structure is observed on three-dimensional (3-D) seismic data from James River, Alberta. The structure has an outer diameter of 4.8 km and a raised central uplift surrounded by a rim synform. The central uplift has a diameter of 2.4 km and its crest appears to be uplifted about 400 m above regional levels. The structure is at a depth of about 4500 m. This is below the zone of economic interest and the feature has not been penetrated by any wells. The disturbed sediments are interpreted to be Cambrian. We infer that the structure was formed in Late Cambrian to Middle Devonian time and suffered erosion before the deposition of the overlying Middle Devonian carbonates. Rim faults, probably caused by slumping of material into the depression, are observed on the outside limb of the synform. Reverse faults are evident underneath the feature and the central uplift appears to have coherent internal reflections. The amount of uplift decreases with increasing depth in the section. The entire feature is interpreted to be a cryptoexplosion structure, possibly caused by a meteorite impact. INTRODUCTION Several enigmatic circular structures, of different sizes and ages, have been observed on seismic data from the Western Canadian sedimentary basin (WCSB) (e.g., Sawatzky, 1976; Isaac and Stewart, 1993) and other parts of Canada (Scott and Hajnal, 1988; Jansa et al., 1989). The structures present startling interruptions in otherwise planar seismic features. -
The Future of Continental Scientific Drilling U.S
THE FUTURE OF CONTINENTAL SCIENTIFIC DRILLING U.S. PERSPECTIVE Proceedings of a workshop | June 4-5, 2009 | Denver, Colorado DOSECC WORKSHOP PUBLICATION 1 Front Cover: Basalts and rhyolites of the Snake River Plain at Twin Falls, Idaho. Project Hotspot will explore the interaction of the Yellowstone hotspot with the continental crust by sampling the volcanic rocks underlying the plain. Two 1.5 km holes will penetrate both the surficial basalt and the underlying rhyolite caldera-fill and outflow depos- its. A separate drill hole will explore the paleoclimate record in Pliocene Lake Idaho in the western Snake River Plain. In addition to the understanding of continent-mantle interaction that develops and the paleoclimate data collected, the project will study water-rock interaction, gases emanating from the deeper curst, and the geomicro- biology of the rocks of the plain. Once scientific objectives and set, budgets are developed, and funding is granted, successful implementation of projects requires careful planning, professional on-site staff, appropriate equip- ment, effective logistics, and accurate accounting. Photo by Tony Walton The authors gratefully acknowledge support of the National Science Foundation (NSF EAR 0923056 to The University of Kansas) and DOSECC, Inc. of Salt Lake City, Utah. Anthony W. Walton, University of Kansas, Lawrence, Kansas Kenneth G. Miller, Rutgers University, New Brunswick, N.J. Christian Koeberl, University of Vienna, Vienna, Austria John Shervais, Utah State University, Logan, Utah Steve Colman, University of Minnesota, Duluth, Duluth, Minnesota edited by Cathy Evans. Stephen Hickman, US Geological Survey, Menlo Park, California covers and design by mitch favrow. Will Clyde, University of New Hampshire, Durham, New Hampshire document layout by Pam Lerow and Paula Courtney. -
Chapter 6 Lawn Hill Megabreccia
Chapter 6 Lawn Hill Megabreccia Chapter 6 Catastrophic mass failure of a Middle Cambrian platform margin, the Lawn Hill Megabreccia, Queensland, Australia Leonardo Feltrin 6-1 Chapter 6 Lawn Hill Megabreccia Acknowledgement of Contributions N.H.S. Oliver – normal supervisory contributions Leonardo Feltrin 6-2 Chapter 6 Lawn Hill Megabreccia Abstract Megabreccia and related folds are two of the most spectacular features of the Lawn Hill Outlier, a small carbonate platform of Middle Cambrian age, situated in the northeastern part of the Georgina Basin, Australia. The megabreccia is a thick unit (over 200 m) composed of chaotic structures and containing matrix-supported clasts up to 260 m across. The breccia also influenced a Mesoproterozoic basement, which hosts the world class Zn-Pb-Ag Century Deposit. Field-studies (undertaken in the mine area), structural 3D modelling and stable isotopic data were used to assess the origin and timing of the megabreccia, and its relationship to the tectonic framework. Previous workers proposed the possible linkage of the structural disruption to an asteroid impact, to justify the extremely large clasts and the conspicuous basement interaction. However, the megabreccia has comparable clast size to some of the largest examples of sedimentary breccias and synsedimentary dyke intrusions in the world. Together with our field and isotope data, the reconstruction of the sequence of events that led to the cratonization of the Centralian Superbasin supports a synsedimentary origin for the Lawn Hill Megabreccia. However, later brittle faulting and veining accompanying strain localisation within the Thorntonia Limestones may represent post-sedimentary, syntectonic deformation, possibly linked to the late Devonian Alice Springs Orogeny. -
The Minor Planet Bulletin
THE MINOR PLANET BULLETIN OF THE MINOR PLANETS SECTION OF THE BULLETIN ASSOCIATION OF LUNAR AND PLANETARY OBSERVERS VOLUME 36, NUMBER 3, A.D. 2009 JULY-SEPTEMBER 77. PHOTOMETRIC MEASUREMENTS OF 343 OSTARA Our data can be obtained from http://www.uwec.edu/physics/ AND OTHER ASTEROIDS AT HOBBS OBSERVATORY asteroid/. Lyle Ford, George Stecher, Kayla Lorenzen, and Cole Cook Acknowledgements Department of Physics and Astronomy University of Wisconsin-Eau Claire We thank the Theodore Dunham Fund for Astrophysics, the Eau Claire, WI 54702-4004 National Science Foundation (award number 0519006), the [email protected] University of Wisconsin-Eau Claire Office of Research and Sponsored Programs, and the University of Wisconsin-Eau Claire (Received: 2009 Feb 11) Blugold Fellow and McNair programs for financial support. References We observed 343 Ostara on 2008 October 4 and obtained R and V standard magnitudes. The period was Binzel, R.P. (1987). “A Photoelectric Survey of 130 Asteroids”, found to be significantly greater than the previously Icarus 72, 135-208. reported value of 6.42 hours. Measurements of 2660 Wasserman and (17010) 1999 CQ72 made on 2008 Stecher, G.J., Ford, L.A., and Elbert, J.D. (1999). “Equipping a March 25 are also reported. 0.6 Meter Alt-Azimuth Telescope for Photometry”, IAPPP Comm, 76, 68-74. We made R band and V band photometric measurements of 343 Warner, B.D. (2006). A Practical Guide to Lightcurve Photometry Ostara on 2008 October 4 using the 0.6 m “Air Force” Telescope and Analysis. Springer, New York, NY. located at Hobbs Observatory (MPC code 750) near Fall Creek, Wisconsin. -
Warfare in a Fragile World: Military Impact on the Human Environment
Recent Slprt•• books World Armaments and Disarmament: SIPRI Yearbook 1979 World Armaments and Disarmament: SIPRI Yearbooks 1968-1979, Cumulative Index Nuclear Energy and Nuclear Weapon Proliferation Other related •• 8lprt books Ecological Consequences of the Second Ihdochina War Weapons of Mass Destruction and the Environment Publish~d on behalf of SIPRI by Taylor & Francis Ltd 10-14 Macklin Street London WC2B 5NF Distributed in the USA by Crane, Russak & Company Inc 3 East 44th Street New York NY 10017 USA and in Scandinavia by Almqvist & WikseH International PO Box 62 S-101 20 Stockholm Sweden For a complete list of SIPRI publications write to SIPRI Sveavagen 166 , S-113 46 Stockholm Sweden Stoekholol International Peace Research Institute Warfare in a Fragile World Military Impact onthe Human Environment Stockholm International Peace Research Institute SIPRI is an independent institute for research into problems of peace and conflict, especially those of disarmament and arms regulation. It was established in 1966 to commemorate Sweden's 150 years of unbroken peace. The Institute is financed by the Swedish Parliament. The staff, the Governing Board and the Scientific Council are international. As a consultative body, the Scientific Council is not responsible for the views expressed in the publications of the Institute. Governing Board Dr Rolf Bjornerstedt, Chairman (Sweden) Professor Robert Neild, Vice-Chairman (United Kingdom) Mr Tim Greve (Norway) Academician Ivan M£ilek (Czechoslovakia) Professor Leo Mates (Yugoslavia) Professor -
Impact Cratering
6 Impact cratering The dominant surface features of the Moon are approximately circular depressions, which may be designated by the general term craters … Solution of the origin of the lunar craters is fundamental to the unravel- ing of the history of the Moon and may shed much light on the history of the terrestrial planets as well. E. M. Shoemaker (1962) Impact craters are the dominant landform on the surface of the Moon, Mercury, and many satellites of the giant planets in the outer Solar System. The southern hemisphere of Mars is heavily affected by impact cratering. From a planetary perspective, the rarity or absence of impact craters on a planet’s surface is the exceptional state, one that needs further explanation, such as on the Earth, Io, or Europa. The process of impact cratering has touched every aspect of planetary evolution, from planetary accretion out of dust or planetesimals, to the course of biological evolution. The importance of impact cratering has been recognized only recently. E. M. Shoemaker (1928–1997), a geologist, was one of the irst to recognize the importance of this process and a major contributor to its elucidation. A few older geologists still resist the notion that important changes in the Earth’s structure and history are the consequences of extraterres- trial impact events. The decades of lunar and planetary exploration since 1970 have, how- ever, brought a new perspective into view, one in which it is clear that high-velocity impacts have, at one time or another, affected nearly every atom that is part of our planetary system. -
Chapter 5: Shock Metamorphism and Impact Melting
5. Shock Metamorphism and Impact Melting ❖❖❖ Shock-metamorphic products have become one of the diagnostic tools of impact cratering studies. They have become the main criteria used to identify structures of impact origin. They have also been used to map the distribution of shock-pressures throughout an impact target. The diverse styles of shock metamorphism include fracturing of crystals, formation of microcrystalline planes of glass through crystals, conversion of crystals to high-pressure polymorphs, conversion of crystals to glass without loss of textural integrity, conversion of crystals to melts that may or may not mix with melts from other crystals. Shock-metamorphism of target lithologies at the crater was first described by Barringer (1905, 1910) and Tilghman (1905), who recognized three different products. The first altered material they identified is rock flour, which they concluded was pulverized Coconino sandstone. Barringer observed that rock flour was composed of fragmented quartz crystals that were far smaller in size than the unaffected quartz grains in normal Coconino sandstone. Most of the pulverized silica he examined passed through a 200 mesh screen, indicating grain sizes <74 µm (0.074 mm), which is far smaller than the 0.2 mm average detrital grain size in normal Coconino (Table 2.1). Fairchild (1907) and Merrill (1908) also report a dramatic comminution of Coconino, although only 50% of Fairchild’s sample of rock flour passed through a 100 mesh screen, indicating grain sizes <149 µm. Heterogeneity of the rock flour is evident in areas where sandstone clasts survive within the rock flour. The rock flour is pervasive and a major component of the debris at the crater. -
Handbook of Iron Meteorites, Volume 1
CHAPTER FOUR Meteorite Craters Nobody has ever witnessed the formation of a meteor meteorites, and (iii) rapidly solidified metallic droplets, ite crater. Interpretations must therefore be based upon analogous to the spheroids encountered in the vicinity of measurement and comparison with artificial craters, caused Meteor Crater, Arizona (Goldstein et al. 1972; Anders et al. by known magnitudes and depths of explosives. Excellent 1973); see page 397. studies have been performed by Baldwin (1949; 1963; The bulk of the typical large lunar craters were formed 1970) who was particularly interested in the puzzling when the kinetic energy ~mv 2 of the impacting body was problems associated with the lunar craters but, as a basis for converted into thermal energy within a fraction of a his speculations, thoroughly examined several terrestrial second, resulting in an explosion. There is a very high craters and presented extensive bibliographies. Results from probability that the impacting body was thereby itself nuclear test sites have been presented by Hansen (1968) totally destroyed, melted or vaporized (Hartman & and Short (1968a, b). Krinov (1960b; 1966a, b) has dis Wood 1971; Ahrens & O'Keefe 1972). Fortunately, for the cussed several craters and impact holes associated with science of meteoritics and for the inhabitants of Earth, our meteorites and also devoted a liuge chapter to the Tunguska atmosphere will alleviate the impact of celestial bodies and comet, which did not produce craters at all. See page 9. through a gradual deceleration cause an important propor Stanyukovich &' Fedynski (1947), Nininger (1952a; 1956), tion to survive as meteorites. However, large and dense Shoemaker (1963) and Gault et al. -
EPSC2018-833, 2018 European Planetary Science Congress 2018 Eeuropeapn Planetarsy Science Ccongress C Author(S) 2018
EPSC Abstracts Vol. 12, EPSC2018-833, 2018 European Planetary Science Congress 2018 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2018 Impact melt boulder from northern Sweden from an unknown source Timmu Kreitsmann (1), Satu Hietala (2), Tapio Soukka (3), Jüri Plado (1), Jari Nenonen (2) and Lauri J. Pesonen (4) (1) Department of Geology, University of Tartu, Estonia ([email protected], [email protected]), (2) Geological Survey of Finland, Finland ([email protected], [email protected]), (3) Oulu Mining School, University of Oulu, Finland ([email protected]) (4) Solid Earth Geophysics Laboratory, Physics Department, University of Helsinki, Finland ([email protected]) Abstract We report an impact melt rock finding from northern Sweden, near the village of Kitkiöjärvi. There is no confirmed meteorite impact structure nearby, thus, the source is currently undiscovered. The impact origin of the finding was confirmed by the presence of planar deformation features (PDFs) in quartz. 1. Introduction Impact cratering is a common and frequent process that affects the planetary surfaces across the solar system throughout geologic time. On Earth, there are 191 confirmed impact structures which are distributed unevenly around the globe. The Fennoscandian Shield houses around 10% of them. Here, we report an impact melt rock finding that originates from an unknown structure in northern Sweden. The semi-rounded impactite boulder, sized 10 × 7 cm, was found by Tapio Soukka in 2017 from a gravel pit at the western side of village Kitkiöjärvi (67°46'16"N 23°03'06"E; Fig. 1). Figure 1: Proven impact structures in Fennoscandia. -
Impact Crater Collapse
P1: SKH/tah P2: KKK/mbg QC: KKK/arun T1: KKK March 12, 1999 17:54 Annual Reviews AR081-12 Annu. Rev. Earth Planet. Sci. 1999. 27:385–415 Copyright c 1999 by Annual Reviews. All rights reserved IMPACT CRATER COLLAPSE H. J. Melosh Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721; e-mail: [email protected] B. A. Ivanov Institute for Dynamics of the Geospheres, Russian Academy of Sciences, Moscow, Russia 117979 KEY WORDS: crater morphology, dynamical weakening, acoustic fluidization, transient crater, central peaks ABSTRACT The detailed morphology of impact craters is now believed to be mainly caused by the collapse of a geometrically simple, bowl-shaped “transient crater.” The transient crater forms immediately after the impact. In small craters, those less than approximately 15 km diameter on the Moon, the steepest part of the rim collapses into the crater bowl to produce a lens of broken rock in an otherwise unmodified transient crater. Such craters are called “simple” and have a depth- to-diameter ratio near 1:5. Large craters collapse more spectacularly, giving rise to central peaks, wall terraces, and internal rings in still larger craters. These are called “complex” craters. The transition between simple and complex craters depends on 1/g, suggesting that the collapse occurs when a strength threshold is exceeded. The apparent strength, however, is very low: only a few bars, and with little or no internal friction. This behavior requires a mechanism for tem- porary strength degradation in the rocks surrounding the impact site. Several models for this process, including acoustic fluidization and shock weakening, have been considered by recent investigations. -
Impact Structures and Events – a Nordic Perspective
107 by Henning Dypvik1, Jüri Plado2, Claus Heinberg3, Eckart Håkansson4, Lauri J. Pesonen5, Birger Schmitz6, and Selen Raiskila5 Impact structures and events – a Nordic perspective 1 Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, NO 0316 Oslo, Norway. E-mail: [email protected] 2 Department of Geology, University of Tartu, Vanemuise 46, 51014 Tartu, Estonia. 3 Department of Environmental, Social and Spatial Change, Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark. 4 Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen, Denmark. 5 Division of Geophysics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki, Finland. 6 Department of Geology, University of Lund, Sölvegatan 12, SE-22362 Lund, Sweden. Impact cratering is one of the fundamental processes in are the main reason that the Nordic countries are generally well- the formation of the Earth and our planetary system, as mapped. reflected, for example in the surfaces of Mars and the Impact craters came into the focus about 20 years ago and the interest among the Nordic communities has increased during recent Moon. The Earth has been covered by a comparable years. The small Kaalijärv structure of Estonia was the first impact number of impact scars, but due to active geological structure to be confirmed in northern Europe (Table 1; Figures 1 and processes, weathering, sea floor spreading etc, the num- 7). First described in 1794 (Rauch), the meteorite origin of the crater ber of preserved and recognized impact craters on the field (presently 9 craters) was proposed much later in 1919 (Kalju- Earth are limited. -
Rocks, Soils and Surfaces: Teacher Guide
National Aeronautics and Space Administration ROCKS, SOILS, AND SURFACES Planetary Sample and Impact Cratering Unit Teacher Guide Goal: This activity is designed to introduce students to rocks, “soils”, and surfaces on planetary worlds, through the exploration of lunar samples collected by Apollo astronauts and the study of the most dominant geologic process across the Solar System, the impact process. Students will gain an understanding of how the study of collected samples and impact craters can help improve our understanding of the history of the Moon, Earth, and our Solar System. Additionally, this activity will enable students to gain experience with scientific practices and the nature of science as they model skills and practices used by professional scientists. Objectives: Students will: 1. Make observations of rocks, “soil”, and surface features 2. Gain background information on rocks, “soil”, and surface features on Earth and the Moon 3. Apply background knowledge related to rocks, soils, and surfaces on Earth toward gaining a better understanding of these aspects of the Moon. This includes having students: a. Identify common lunar surface features b. Create a model lunar surface c. Identify the three classifications of lunar rocks d. Simulate the development of lunar regolith e. Identify the causes and formation of impact craters 4. Design and conduct an experiment on impact craters 5. Create a plan to investigate craters on Earth and on the Moon 6. Gain an understanding of the nature of science and scientific practices by: a. Making initial observations b. Asking preliminary questions c. Applying background knowledge d. Displaying data e. Analyzing and interpreting data Grade Level: 6 – 8* *Grade Level Adaptations: This activity can also be used with students in grades 5 and 9-12.