This list of more than 130 features on Earth includes candidate impact sites that have appeared several times in the literature and/or have been endorsed by the Impact Field Studies Group (IFSG)[1] and/or Expert Database on Earth Impact Structures (EDEIS),[2]. None has been scientifically confirmed to be an impact crater, according to the Earth Impact Database (EID).[3]
The Impact Field Studies Group (IFSG) is a scientific organization emphasizing geologic field research of suspected and confirmed sites of impact craters and impact structures. The group is composed of researchers, professionals and students involved in study of impact sites. IFSG's web site is hosted by the Department of Earth and Planetary Sciences at University of Tennessee, Knoxville.
The Earth Impact Database is a database of confirmed impact structures or craters on Earth. It was initiated in 1955 by the Dominion Observatory, Ottawa, under the direction of Dr. Carlyle S. Beals. Since 2001, it has been maintained as a not-for-profit source of information at the Planetary and Space Science Centre at the University of New Brunswick, Canada.
The following tables list geological features on Earth that some individuals have associated with impact events, but for which there is currently no confirming scientific evidence in the peer-reviewed literature. In order for a structure to be a confirmed as an impact crater, it must meet a stringent set of well established criteria. Some proposed impact structures are eventually confirmed, whereas others are shown to be misidentified (see below). Recent extensive surveys have been done for Australian (2005),[4] African (2014),[5] and South American (2015)[6] craters, as well as those in the Arab world (2016).[7] A book review by A. Crósta and U. Reimold disputes some of the evidence presented for several of the South American structures.[8]
The Cheko crater is thought by one research group to be the result of the famous Tunguska event, although sediments in the lake have been dated back more than 5,000 years. There is highly speculative conjecture about the supposed Sirente impact (c. 320 ± 90 AD) causing the Roman emperor Constantine's vision at Milvian Bridge.[131]
Lake Cheko is a small freshwater lake in Siberia, near the Podkamennaya Tunguska River, in what is now the Evenkiysky District of the Krasnoyarsk Krai.
The Tunguska event was a large explosion that occurred near the Stony Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908 (NS). The explosion over the sparsely populated Eastern Siberian Taiga flattened 2,000 square kilometres of forest, yet caused no known human casualties. The explosion is generally attributed to the air burst of a meteor. It is classified as an impact event, even though no impact crater has been found; the object is thought to have disintegrated at an altitude of 5 to 10 kilometres rather than to have hit the surface of the Earth.
The Sirente crater is a small shallow seasonal lake in Abruzzo, central Italy. The depression, which is located at the center of the Prati del Sirente, a mountainous highland north of the Sirente massif in the Apennines, is 13 km (8.1 mi) from the village of Secinaro. Its formation has prompted a number of theories in recent years. Although in the absence of shock-metamorphic and / or geochemical evidence it is not yet possible to confirm the meteoritic impact theory, no other theories for the origin of this geological structure have been proven yet.
Umm al Binni lake is a mostly dry lake within the Central Marshes in Maysan Governorate in southern Iraq. The 3.4 km wide lake is approximately 45 km northwest of the Tigris–Euphrates confluence. Because of its shape, location, and other details, it has been conjectured to represent an impact crater.
Sumer is the earliest known civilization in the historical region of southern Mesopotamia, modern-day southern Iraq, during the Chalcolithic and Early Bronze ages, and one of the first civilizations in the world along with Ancient Egypt and the Indus Valley. Living along the valleys of the Tigris and Euphrates, Sumerian farmers were able to grow an abundance of grain and other crops, the surplus of which enabled them to settle in one place. Prehistoric proto-writing dates back before 3000 BC. The earliest texts, from c. 3300 BC, come from the cities of Uruk and Jemdet Nasr; early cuneiform script emerged around 3000 BC.
Sanskrit is a language of ancient India with a history going back about 3,500 years. It is the primary liturgical language of Hinduism and the predominant language of most works of Hindu philosophy as well as some of the principal texts of Buddhism and Jainism. Sanskrit, in its variants and numerous dialects, was the lingua franca of ancient and medieval India. In the early 1st millennium CE, along with Buddhism and Hinduism, Sanskrit migrated to Southeast Asia, parts of East Asia and Central Asia, emerging as a language of high culture and of local ruling elites in these regions.
Bloody Creek crater, which is also known as the Bloody Creek structure, is a 420-by-350-meter in diameter elliptical feature that is located in southwestern Nova Scotia, Canada. It is argued to be either a possible extraterrestrial impact crater or an impact structure. It lies between Bridgetown and West Dalhousie, Annapolis County, Nova Scotia, where the Bloody Creek structure straddles what was once a stretch of Bloody Creek. It also is informally known as the Astrid crater.
Hiawatha Glacier is a glacier in northwest Greenland, near Inglefield Land. It was mapped in 1922 by Lauge Koch, who noted that the glacier tongue extended into Lake Alida. Hiawatha Glacier attracted attention in 2018 because of the discovery of a crater beneath the surface of the ice sheet in the area. A publication noted in 1952 that Hiawatha Glacier is retreating since 1920.
The Younger Dryas was a return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum started receding around 20,000 BP. It is named after an indicator genus, the alpine-tundra wildflower Dryas octopetala, as its leaves are occasionally abundant in the Late Glacial, often minerogenic-rich, like the lake sediments of Scandinavian lakes.
As the trend in the Earth Impact Database for about 26 confirmed craters younger than a million years old show that almost all are less than twokm (1.2mi) in diameter (except the threekm (1.9mi) Agoudal and fourkm (2.5mi)Rio Cuarto), the suggestion that two large craters, Mahuika (20km (12mi)) and Burckle (30km (19mi)), formed just within the last few millennia has been met with skepticism.[135][136][137]
Mahuika crater is a submarine feature that is hypothesized to be an impact crater. It is about 20 ± 2 km wide and over 153 meters (502 ft) deep and lies on the New Zealand continental shelf at 48.3 South and 166.4 East, to the south of The Snares. The Mahuika crater is named after the Māori god of fire. However, there is debate about its origins.
However, the source of the young (less than a million years old) and enormous Australasian strewnfield (c. 790 ka) is suggested to be a crater about 100km (62mi) across somewhere in Indochina,[138][139] with Hartung and Koeberl (1994) proposing the elongated 100km ×35km (62mi ×22mi)Tonlé Sap lake in Cambodia (visible in the map at the side) as a suspect structure.[140]
Some confirmed impacts like Sudbury or Chicxulub are also sources of magnetic anomalies[143] and/or gravity anomalies. The magnetic anomalies Bangui and Jackpine Creek,[73] the gravity anomalies Wilkes Land crater and Falkland Islands,[55] and others have been considered as being of impact origin. Bangui apparently has been discredited,[31][144] but appears again in a 2014 table of unconfirmed structures in Africa by Reimold and Koeberl.[5]
The Eltanin impact has been confirmed (via an iridium anomaly and meteoritic material from ocean cores) but, as it fell into the Pacific Ocean, apparently no crater was formed. The age of Silverpit and the confirmed Boltysh crater (65.17 ± 0.64 Ma), as well as their latitude, has led to the speculative hypothesis that there may have been several impacts during the KT boundary.[145][146] Of the five oceans in descending order by area, namely the Pacific, Atlantic, Indian, Antarctic, and Arctic, only the smallest (the Arctic) does not yet have a proposed unconfirmed impact crater.
Craters larger than 100km in the Phanerozoic (after 541 Ma) are notable for their size as well as for the possible coeval events associated with them especially the major extinction events.
There is geological evidence for impact events having taken place on Earth on certain specific occasions, which should have formed craters, but for which no impact craters have been found. In some cases this is because of erosion and Earth's crust having been recycled through plate tectonics, in others likely because exploration of the Earth's surface is incomplete. Typically the ages are already known and the diameters can be estimated.
The presence of shock metamorphism and shatter cones are important criteria in favor of an impact interpretation, though massive landslides (such as the Köfels landslide of 7800 BC which was once thought to be impact-related) may produce shock-like fused rocks called "frictionite".[158]
An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters range from small, simple, bowl-shaped depressions to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.
Aorounga is an eroded meteorite impact crater in Chad, Africa. The exposed remnant of the crater is 12.6 km (7.8 mi) in diameter and its age is estimated to be less than 345 million years.
The Arkenu structures, also known as the Arkenu craters, are a pair of prominent circular geological structures. These structures are 10 km and 6.8 km in diameter, and lie about 70 km west of Jabal Arkanu on the eastern margin of the al-Kufrah Basin.
Connolly Basin is a 9 km-diameter impact crater located in the Gibson Desert of central Western Australia. It lies adjacent to the Talawana Track 45 km west of the junction with the Gary Highway, but is difficult to access due to the remoteness of the area. It was originally thought to be a diapir ; an impact origin was first proposed in 1985.,
Gweni-Fada is a meteorite crater in Chad, Africa.
Mount Toondina crater is an impact structure, the eroded remnant of a former impact crater, situated in northern South Australia 45 km south of the township of Oodnadatta. Mount Toondina is the high point of a circular topographic feature rising out of an otherwise relatively flat desert area of the Eromanga Basin. An impact origin was first suggested in 1976, challenging the earlier diapir hypothesis, and strongly supported by subsequent studies. A geophysical survey using gravity methods indicates an internal structure typical of complex impact craters, including an uplifted centre, and suggests that the original crater was about 3–4 km in diameter. The crater must be younger than the Early Cretaceous age of the rocks in which it is situated, but otherwise is not well dated. It has clearly undergone significant erosion since the impact event.
The Rochechouart crater is an impact crater. The initial crater morphology has been lost by erosion and there is no crater visible on site. The proper term to designate what remains of the Rochechouart impact crater is Rochechouart impact structure. The term “astrobleme” introduced by R. Dietz since 1947 together with shatter cones as a symptomatic finger print for identifying an eroded impact crater on Earth, is also used to designate the Rochechouart impact structure. In 2008 the French State acknowledged the heritage value of the Rochechouart impact creating the “Réserve Naturelle Nationale de l’astroblème de Rochechouart-Chassenon” on 12 sites representative of characteristics geological features of the impact structure.
Roter Kamm is a meteorite crater, located in the Sperrgebiet, within the Namibian section of the Namib Desert, approximately 80 kilometres (50 mi) north of Oranjemund and 12 kilometres (7.5 mi) southwest of Aurus Mountain in the ǁKaras Region. The crater is 2.5 kilometres (1.6 mi) in diameter and is 130 metres (430 ft) deep. The age is estimated at 4.81 ± 0.5 Ma, placing it in the Pliocene. The crater is exposed at the surface, but its original floor is covered by sand deposits at least 100 metres (330 ft) thick.
Tookoonooka is a large meteorite impact crater (astrobleme) situated in South West Queensland, Australia. It lies deeply buried within Mesozoic sedimentary rocks of the Eromanga Basin and is not visible at the surface.
Woodleigh is a large meteorite impact crater (astrobleme) in Western Australia, centred on Woodleigh Station east of Shark Bay, Gascoyne region. A team of four scientists at the Geological Survey of Western Australia and the Australian National University, led by Arthur J. Mory, announced the discovery in the 15 April 2000 issue of Earth and Planetary Science Letters.
The term cryptoexplosion structure means an explosion of unknown cause. The term is now largely obsolete. It was once commonly used to describe sites where there was geological evidence of a large-scale explosion within the Earth's crust, but no definitive evidence for the cause such as normal volcanic rocks. These sites are usually circular with signs of anomalous rock deformation contrasting with the surrounding region, and often showing evidence that crustal material had been uplifted and/or blown outwards. The assumption was that some unusual form of volcanism, or a gas explosion originating within the crust, was the cause. The use of the term went away with the rise of the science of impact crater recognition in the late 20th century. Most structures described as cryptoexplosions turned out to be eroded impact craters, caused by the impact of meteorites. Today geologists discount former cryptoexplosion theories.
Serra da Cangalha is an impact crater in the State of Tocantins, near the border of Maranhão State, in north/northeastern Brazil. The crater is between 12 and 13 kilometres in diameter, making it the second-largest known crater in Brazil. Its age is estimated to be about 220 million years. The name means Pack-Saddle Mountains in Portuguese.
The Australasian strewnfield is the youngest and largest of the tektite strewnfields, with recent estimates suggesting it may cover 10%-30% of the Earth's surface.
An impact structure is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface whatever the stage of erosion of the structure. In contrast an impact crater is the surface expression of an impact structure. In many case, in many cases on Earth, the impact crater has been destroyed by erosion leaving only the deformed rock or sediment of the impact structure behind. This is the fate of almost all old impact craters on Earth, unlike the ancient pristine craters preserved on the Moon and other geologically inactive rocky bodies with old surfaces. in the Solar System. Impact structure is synonymous with the less commonly used term astrobleme meaning "star wound".
Mars may contain ores that would be very useful to potential colonists. The abundance of volcanic features together with widespread cratering are strong evidence for a variety of ores. While nothing may be found on Mars that would justify the high cost of transport to Earth, the more ores that future colonists can obtain from Mars, the easier it would be to build colonies there.
The Late Heavy Bombardment is an event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. During this interval, a disproportionately large number of asteroids are theorized to have collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth, and Mars.
The Noachian is a geologic system and early time period on the planet Mars characterized by high rates of meteorite and asteroid impacts and the possible presence of abundant surface water. The absolute age of the Noachian period is uncertain but probably corresponds to the lunar Pre-Nectarian to Early Imbrian periods of 4100 to 3700 million years ago, during the interval known as the Late Heavy Bombardment. Many of the large impact basins on the Moon and Mars formed at this time. The Noachian Period is roughly equivalent to the Earth’s Hadean and early Archean eons when the first life forms likely arose.
In summer 1965, the first close-up images from Mars showed a cratered desert with no signs of water. However, over the decades, as more parts of the planet were imaged with better cameras on more sophisticated satellites, Mars showed evidence of past river valleys, lakes, and present ice in glaciers and in the ground. It was discovered that the climate of Mars displays huge changes over geologic time because its axis is not stabilized by a large moon, as Earth's is. Also, some researchers maintain that surface liquid water could have existed for periods of time due to geothermal effects or asteroid impacts. This article describes some of the places that could have held large lakes.
↑ Maximiliano C.L. Rocca et al. (2017). (2017). "Geophysical evidence for a large impact structure on the Falkland (Malvinas) Plateau". Terra Nova. 29 (4): 233–237. doi:10.1111/ter.12269.
↑ R. Iaskty and A. Glikson (2005). "Gnargoo: a possible 75 km-diameter post-Early Permian – pre-Cretaceous buried impact structure, Carnarvon Basin, Western Australia", Australian Journal of Earth Sciences, Vol 52, 2005
1 2 Frank Dachille (1976). (1976). "Frequency of the formation of large terrestrial impact craters". Meteoritics. 11: 270. Bibcode:1976Metic..11..270D.
1 2 Zeylik B. S.; Seytmuratova E. Yu, 1974: A meteorite-impact structure in central Kazakhstan and its magmatic-ore controlling role. Doklady Akademii Nauk SSSR: 1, Pages 167–170
↑ Wang, K.; Geldsetzer, H. H. J. (1992). "A late Devonian impact event and its association with a possible extinction event on Eastern Gondwana". Lunar and Planetary Inst., International Conference on Large Meteorite Impacts and Planetary Evolution: 77. Bibcode:1992lmip.conf...77W.
↑ Garde, Adam A.; McDonald, Iain; Dyck, Brendan; Keulen, Nynke (2012). "Searching for giant, ancient impact structures on Earth: The Mesoarchaean Maniitsoq structure, West Greenland". Earth and Planetary Science Letters. 337–338: 197–210. Bibcode:2012E&PSL.337..197G. doi:10.1016/j.epsl.2012.04.026.
↑ Scherst, Anders; Garde, Adam A. (30 July 2013). "Complete hydrothermal re-equilibration of zircon in the Maniitsoq structure, West Greenland: A 3001 Ma minimum age of impact?". Meteoritics & Planetary Science. 48 (8): 1472–1498. Bibcode:2013M&PS...48.1472S. doi:10.1111/maps.12169.
↑ Master, S. (2002) Umm al Binni lake, a possible Holocene impact structure in the marshes of southern Iraq. In: Leroy, S. and Stewart, I.S. (Eds.), Environmental Catastrophes and Recovery in the Holocene, Abstracts Volume, Brunel University, UK, 29 August – 2 September 2002, pp.56–57
↑ Stevens, G, I Spooner, J Morrow, P Pufahl, R Raeside, RAF Grieve, CR Stanley, SM Barr, and D McMullin (2008) Physical evidence of a late-glacial (Younger Dryas?) impact event in southwestern Nova Scotia. Atlantic Geology. 44:42.
↑ Jolley D., Gilmour I., Gurov E., Kelley S., Watson J. (2010) Two large meteorite impacts at the Cretaceous-Paleogene boundary Geology September 2010, v. 38, pp.835–838, doi:10.1130/G31034.1
↑ Becker L., Shukolyukov A., Macassic C., Lugmair G. & Poreda R. 2006. Extraterrestrial Chromium at the Graphite Peak P/Tr boundary and in the Bedout Impact Melt Breccia. Lunar and Planetary Science XXXVII (2006), abstract # 2321.PDF
↑ Weidinger JT, Korup O (2008). "Frictionite as evidence for a large Late Quaternary rockslide near Kanchenjunga, Sikkim Himalayas, India — Implications for extreme events in mountain relief destruction". Geomorphology. 103 (1): 57–65. Bibcode:2009Geomo.103...57W. doi:10.1016/j.geomorph.2007.10.021.
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