The following tables list geological features on Earth that are possible impact events, but for which there is currently no confirming scientific evidence in the peer-reviewed literature. In order for a structure to be confirmed as an impact crater, it must meet a stringent set of well-established criteria. Some proposed impact structures are likely to eventually be confirmed, whereas others are likely to be shown to have been misidentified (see below). Recent extensive surveys have been done for Australian (2005),[1] African (2014),[2] and South American (2015)[3] craters, as well as those in the Arab world (2016).[4] A book review by A. Crósta and U. Reimold disputes some of the evidence presented for several of the South American structures.[5]
Russia's Lake Cheko 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) having caused the Roman emperor Constantine's vision at Milvian Bridge.[313][better source needed]
Shortly after the Hiawatha Crater was discovered, researchers suggested that the impact could have occurred as late as ~12,800 years ago, leading some to associate it with the controversial Younger Dryas impact hypothesis (YDIH).[317] James Kennett, a leading advocate of the YDIH said, "I'd unequivocally predict that this crater is the same age as the Younger Dryas."[318]
These claims were criticised by other scholars. According to impact physicist Mark Boslough writing for Skeptical Inquirer the first reports of the impact released by science journalist Paul Voosen focused on this being a young crater which according to Boslough "set the tone for virtually all the media reporting to follow". Boslough argued, based on evidence and statistical probability, that once the crater has been drilled and researched "it will turn out to be much older." He complained that this important discovery "was tainted by connections to a widely discredited hypothesis and speculations that did not make it through peer review".[318][319] The YDIH has since been refuted comprehensively by a team of earth scientists and impact experts.[320]
A 2022 study using Argon–Argon dating of shocked zircon crystals in impact melt rocks found outwash less than 10 km downstream of the glacier pushed the estimate back to around 57.99 ± 0.54 million years ago, during the late Paleocene.[321][322] Confirmation would require drilling almost one km (3,300 ft) through the ice sheet above the crater to obtain a sample of dateable, solidified impact melt from the crater.
As the trend in the Earth Impact Database for about 26 confirmed craters younger than a million years old shows that almost all are less than two km (1.2 mi) in diameter (except the three km (1.9 mi) Agoudal and four km (2.5 mi) Rio Cuarto), the suggestion that two large craters, Mahuika (20 km (12 mi)) and Burckle (30 km (19 mi)), formed only within the last few millennia has been met with skepticism.[324][325][326] 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 100 km (62 mi) across somewhere in Indochina,[327][328] with Hartung and Koeberl (1994) proposing the elongated 100 km × 35 km (62 mi × 22 mi) Tonlé Sap lake in Cambodia (visible in the map at the side) as a suspect structure.[329]
Some confirmed impacts like Sudbury or Chicxulub are also sources of magnetic anomalies[333] and/or gravity anomalies. The magnetic anomalies Bangui and Jackpine Creek,[134] the gravity anomalies Wilkes Land crater and Falkland Islands,[334] and others have been considered as being of impact origin. Bangui apparently has been discredited,[87][335] but appears again in a 2014 table of unconfirmed structures in Africa by Reimold and Koeberl.[2]
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.[336][337] 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 100 kilometres (62 mi) 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, or because no actual crater was formed because the impacting object exploded as a cosmic air burst. 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".[362]
^Acevedo, R.; Rocca, M. C.; Ponce, J.; Stinco, S. (2015). Impact Craters in South America. SpringerBriefs in Earth Sciences. Springer. ISBN978-3-319-13092-7.
^Garvin, James B.; Blodget, Herbert W. (1986). "Suspected Impact Crater Near Al Madafi, Saudi Arabia". Meteoritics. 21: 366. Bibcode:1986Metic..21..366G.
^Zeilik, B. S. (1987). "The Arganaty cosmogenic crater in southern Kazakhstan and the ring structures associated with it". Akademiia Nauk SSSR, Doklady. 297 (4): 925–928. Bibcode:1987DoSSR.297..925Z.
^Papagiannis, Michael D. (1989). "Photographs from geostationary satellites indicate the possible existence of a huge 300 KM impact crater in the Bohemian region of Czechoslovakia". Meteoritics. 24: 313. Bibcode:1989Metic..24R.313P.
^Rajlich, P. (1992). "Bohemian Circular Structure, Czechoslovakia: Search for the Impact Evidence". Abstracts of Papers Presented to the International Conference on Large Meteorite Impacts and Planetary Evolution. Held August 31 – September 2, 1992, in Sudbury, Ontario, Canada. Vol. 790. Lunar and Planetary Institute. p. 57. Bibcode:1992LPICo.790...57R. LPI Contribution 790. {{cite book}}: |journal= ignored (help)
^King, D.T., Jr., and Petruny, L.W.. 2007. Impact structures and craters of the U.S. Gulf coastal states.Gulf Coast Association of Geological Societies Transactions. v. 57, p. 409-425.
^Matherne, C., Karunatillake, S., Hood, D.R., Duxbury, J., Herr, A., Heinrich, P., Horn, M., Webb, A. and Sivils, A., 2020. Planar Deformation Features Found Within a Possible Impact Structure, the Brushy Creek Feature, St. Helena Parish, LA.Lunar and Planetary Science Conference No. 2326, p. 2361.
^Quek, Long Xiang; Ghani, A. A; Badruldin, Muhammad Hafifi; Mokhtar, Saidin; Harith, Zuhar Zahir; Roselee, M. Hatta (2015). "Platinum Group Elements in Proximal Impactites of the Bukit Bunuh Impact Structure, Malaysia". Current Science. 109 (12): 2303. doi:10.18520/v109/i12/2303-2308 (inactive 1 July 2025).{{cite journal}}: CS1 maint: DOI inactive as of July 2025 (link)
^ abAbbott, Dallas H., Martos, Suzanne, Elkinton, Hannah, Bryant, Edward F., Gusiakov, Viacheslav, and Breger, Dee (2006). Impact craters as sources of megatsunami generated chevron dunes. 2006 Philadelphia Annual Meeting (22–25 October 2006)
^Masse W. B., Bryant E., Gusiakov V., Abbott D., Rambolamanana G., Raza H., Courty M.A. (2006). Holocene Indian ocean cosmic impacts – the megatsunami chevron evidence from southern Madagascar. AGU, San Francisco
^Brandsma Dan, Lund Steve P.; Henyey Thomas, L. (1989). "Paleomagnetism of Late Quaternary marine sediments from Santa Catalina basin, California continental borderland ". J. Geophys. Res. B. 94 (1): 547–564. Bibcode:1989JGR....94..547B. doi:10.1029/JB094iB01p00547.
^Holcombe, Troy L.; Warren, John S.; Reid, David F.; Virden, William T.; Divins, David L. (2001). "Small Rimmed Depression in Lake Ontario: An Impact Crater?". Journal of Great Lakes Research. 27 (4): 510–517. Bibcode:2001JGLR...27..510H. doi:10.1016/S0380-1330(01)70664-8.
^Holcombe, Troy L.; Youngblut, Scott; Slowey, Niall (2013). "Geological structure of Charity Shoal crater, Lake Ontario, revealed by multibeam bathymetry". Geo-Marine Letters. 33 (4): 245–252. Bibcode:
![Kondyor Massif or Konder (an igneous intrusion)[363]](File:Kondyor-view.jpg)
![The Richat structure (a geologic dome)[364]](File:ASTER_Richat.jpg)
