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27:
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120:, Allen noticed an unusual set of concentric rings. Thinking they resembled a meteor-strike but lacking experience in impact structures, he hung an image of them on the wall of his office, hoping someone else might be able to shed light on the mystery. Stewart, who had long predicted that a crater would be found on 3D seismic data, saw the image and suggested it might be an impact feature. The discovery of the crater and the impact hypothesis were reported in the journal
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20:
411:, and deposits from the hypothesised tsunami, which might be found anywhere around the North Sea basin. As well as allowing a more accurate age determination, finding such evidence would also strengthen the impact hypothesis. Two nearby oil exploration wells penetrate the ring system, yet cutting samples from these fail to provide any independent support for the meteor theory, thus weakening the case for it being due to an extraterrestrial body.
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sediment. The
Cretaceous Period ended about 66 million years ago, but, on the evidence of nearby boreholes, the lowermost Paleogene sediments appear to be absent. Thus the age of the Silverpit event was initially stated to lie somewhere between 66 and 60 million years before present. However, after a
476:
While this scenario may have occurred on Earth 66 million years ago, evidence for this hypothesis is not strong. In particular, the ages of some of the possibly related craters are only known to an accuracy of a few million years. Also, the now widely held previously stated belief that
Silverpit was
371:
The position of the crater within the layers of rock and sediment on the sea floor could in theory be used to constrain its age: sediments laid down before the crater's formation might conceivably be disturbed by the impact, while those laid down afterwards will not. In their discovery paper, Allen
311:
One possibility is that after the impact excavated a bowl-shaped depression, soft material surrounding it slumped towards the centre, leaving the concentric rings. It is thought that for this to happen, the soft material would have to be quite a thin layer, with more brittle material on top. A thin
270:
Silverpit crater is about 3 km (1.9 mi) wide at the top
Cretaceous level. Unusually for a terrestrial crater, it is surrounded by a set of concentric rings, which extend to about 10 km (6.2 mi) radius from the centre. These rings give the crater a somewhat similar appearance to
324:
If one assumes the meteor impact theory is right, the size of the crater can be combined with assumptions about the speed of an impacting object to estimate the size of the impactor itself. Impacting objects are generally moving at speeds of the order of 20–50 km/s (12–31 mi/s), and at
157:
Only three years before the announcement of the discovery of the
Silverpit crater, it had been suggested that seismic data from the North Sea would have a good chance of containing evidence of an impact crater: given the rate of crater formation on the Earth and the size of the North Sea, the
253:
In
October 2009, an open debate of the notion that "the Silverpit Crater was formed by meteor impact" was held at the Geological Society of London. Simon Stewart gave the case for the motion and John Underhill presented the case against. The outcome was overwhelming support for Underhill's
291:
tend to be much larger than
Silverpit, and so, if the impact hypothesis is correct, the origin of Silverpit's rings is subject to debate. A complicating factor is that almost all known impact craters are on land, despite the fact that two-thirds of impacting objects will land in
406:
method of estimating the age of a crater is somewhat crude and imprecise, and the result is questioned by
Underhill's non-impact hypothesis. Assuming an impact origin, other possible ways of dating the event include looking for evidence of ejecta material such as
232:
In 2007, Underhill continued to present evidence that he argues does not support the impact hypothesis. After analyzing seismic data over a wide region, he proposed that
Silverpit was just one of many similar features related to the withdrawal of the Permian-age
199:
layers of rock beneath the crater appeared to be undisturbed. Another strong indication that an impact had created the crater was the presence of a central peak – something that
Stewart & Allen contend is difficult to form except through a meteorite impact.
153:
up to 1,500 m (4,900 ft) thick, which forms the bed of the North Sea at a depth of about 40 m (130 ft). Stewart and Allen's studies suggest that at the time of its formation, the area was under 50 to 300 m (160 to 980 ft) of water.
414:
Analysis of samples taken directly from the central crater would also assist age determination as well as confirm one or other of the proposed theories; until this has occurred
Silverpit cannot be confirmed as an impact structure.
243:
Underhill then focused his research attention upon understanding why the salt moves where it does when it does and why the so-called crater took the form that it did. This led him to publish a peer-review article in the journal,
481:
impact reduces the possibility of it being involved in this hypothesis. Even if it were formed by bolide impact, the increased uncertainty in the age estimate for Silverpit to 74–45 million years further weakens the hypothesis.
228:
folded, and that sediments of Tertiary age at the crater onlap its sides and thicken into its axis, suggesting that the salt was moving (a process called halokinesis) while Tertiary sediments were being laid down.
190:
anomalies in the crater, which would be expected if eruptions had occurred there. Withdrawal of salt deposits below the crater, known to be a mechanism for the formation of some craters, was ruled out because the
312:
layer of mobile material beneath a solid crust is easy to understand in the context of icy moons, but is not a common occurrence on the rocky bodies of the solar system. One suggestion is that overpressured
105:
A perspective view of the top chalk surface, looking north-east, showing the central crater and its surrounding rings. False colours indicate depth (red/yellow=shallow; blue/purple=deep).
220:, led to the counterproposal that withdrawal of Upper Permian (Zechstein Supergroup) salt at depth was in fact a better explanation. Underhill found that all layers of rock down to the
465:
with Jupiter in 1994 proved that gravitational interactions can fragment a comet, giving rise to many impacts over a period of a few days if the comet fragments should collide with a
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The early estimate of the age of the Silverpit event, stated as 66–60 million years before present, overlaps with the age of the Chicxulub impact near the northwest corner of the
363:. Scientists are currently searching for any evidence of large tsunamis in the surrounding areas dating from around that time, but no such evidence has been uncovered yet.
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Other authors have disputed its extraterrestrial origin. An alternative origin was proposed in which the feature was created by withdrawal of rock support by
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20°N and 70°N, leading to the speculative hypothesis that the Chicxulub impact may have been only one of several impacts that happened all at the same time.
866:
Underhill J.R. (2009). "Role of intrusion-induced salt mobility in controlling the formation of the enigmatic "Silverpit Crater", UK Southern North Sea".
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more detailed appraisal of the seismic data, Allen and Stewart gave a more cautious estimate of the age as between 74 and 45 million years (Late
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K. Thomson; P. Owen; K. Smith (2005). "Discussion on the North Sea Silverpit Crater: impact structure or pull-apart basin?".
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in August 2009 in which he outlined the evidence for an intrusion-related salt withdrawal cause for the feature's formation.
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Stewart, S. A. & Allen, P. J. (2005). "3D seismic reflection mapping of the Silverpit multi-ringed crater, North Sea".
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Other mechanisms for producing a crater were considered and rejected by Allen and Stewart when they discovered the crater.
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Seismic data showing the crater and its concentric ring structure (Image credit:Phil Allen (PGL) and Simon Stewart (BP))
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An object 120 m (390 ft) across smashing into the sea at many kilometers per second would generate enormous
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in 1908 is thought to have been a comet or asteroid about 60 m (200 ft) across, with a mass of about 4
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is estimated to have measured approximately 9.6 km (6 miles) across, while the object responsible for the
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The origin of the crater is debated by the Geoscience community with alternate theories of salt withdrawal and
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The crater-like structure was discovered by petroleum geoscientists Simon Stewart and Philip Allen. Analyzing
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Its origin as a meteor impact structure was first proposed and widely reported in 2002. It would be the first
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Allen P.J.; Stewart S.A. (2003). "Silverpit: the morphology of a terrestrial multi-ringed impact structure".
74:. Its age was proposed to lie somewhere in a 29-million-year interval between 74 and 45 million years (Late
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10 lb) would be required to form a Silverpit-sized crater, if the object was rocky. If it had been a
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Collins G.S.; Turtle E.P.; Melosh H.J. (2003). "Numerical Simulations of Silverpit Crater Collapse".
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Stewart SA, Allen PJ (2002). "A 20-km-diameter multi-ringed impact structure in the North Sea".
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454:. Several other large impact craters of around the same age have been discovered, all between
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K. Smith (2004). "The North Sea Silverpit Crater: impact structure or pull-apart basin?".
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Underhill J.R. (2004). "Earth science: an alternative origin for the 'Silverpit crater'".
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these speeds an object about 120 m (390 ft) across and with a mass of 2.0
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proposed, raising doubts as to Silverpit's categorization as an impact structure.
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are much less well established than those of impacts on land. Compare the
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salt. This result was presented at the April 2007 annual meeting of the
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522:(Ullapool bolide), another proposed impact crater in the British Isles
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952:
Impact Cratering: Bridging the Gap Between Modeling and Observations
500:, the Silverpit's area which was above sea level in human prehistory
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469:. Comets frequently undergo gravitational interactions with the
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Analysis of regional 2D seismic lines and 3D seismic volumes by
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fishing grounds in which it is located. The name is given by
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below the surface may have acted as the soft mobile layer.
308:, probably the most thoroughly studied marine impact zone.
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in the bed of the North Sea, which is thought to be an old
618:
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alternative genesis through melt-induced salt withdrawal.
1138:
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Further information from the Geological Society of London
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Foschini L. (1999). "A solution for the Tunguska event".
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297:
516:, a 145 million years impact crater in the Barents sea.
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340:
For comparison, the object which struck the Earth at
733:"Unusually Well Preserved Crater Found in North Sea"
113:data for a region 130 km (81 mi) off the
1008:"Double space strike 'caused dinosaur extinction'"
602:Unusually Well Preserved Crater Found in North Sea
59:data collected during exploration for gas in the
1789:
842:
372:and Stewart stated that Silverpit was formed in
149:. The structure currently lies below a layer of
145:formed while the sea level was lower during the
865:
718:"The Geological Society of London - Silverpit"
663:
1246:
1232:
1124:
902:"Geological Society – Silverpit "not crater""
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224:(with an age of about 250 million years) are
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386:, but is covered by an undisturbed layer of
239:American Association of Petroleum Geologists
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509:List of possible impact structures on Earth
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1131:
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427:Silverpit bears a stronger resemblance to
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859:
494:, an impact crater also discovered by BP.
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604:, National Geographic News, 31 July 2002
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204:Evidence for alternative interpretations
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43:is a buried sub-sea structure under the
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622:Geological Society of America Bulletin
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337:, the crater would have been larger.
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129:Silverpit crater is named after the
61:Southern North Sea Sedimentary Basin
1084:UK's first impact crater discovered
1035:"What Really Killed the Dinosaurs?"
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747:
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532:
186:was excluded because there were no
178:Evidence in favour of impact origin
13:
1094:David Darling's space encyclopedia
1060:"North Sea crater shows its scars"
845:"UK impact crater debate heats up"
843:Fildes, Jonathan (30 March 2007).
650:
439:than it does to other terrestrial
14:
1834:
1077:
799:Journal of the Geological Society
756:Journal of the Geological Society
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1333:
1099:The Geological Society of London
1033:Black, Riley (7 February 2013).
162:of impact craters would be one.
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18:
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1000:
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300:, so the results of impacts on
47:off the coast of the island of
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1:
1818:Cretaceous–Paleogene boundary
1770:Lunar and Planetary Institute
1602:Cretaceous–Paleogene boundary
735:. news.nationalgeographic.com
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968:Astronomy & Astrophysics
306:Chesapeake Bay impact crater
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91:Geological Society of London
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1662:Planar deformation features
925:Lunar and Planetary Science
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10:
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1823:Landforms of the North Sea
1765:Impact Field Studies Group
600:Stentor Danielson (2002).
419:Multiple impact hypothesis
1798:Cretaceous impact craters
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1248:Impact cratering on Earth
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1813:Paleocene impact craters
1808:Impact craters of Europe
1735:William Kenneth Hartmann
1401:Clearwater East and West
1349:Confirmed≥20 km diameter
1089:National Geographic news
1652:Ordovician meteor event
991:1999A&A...342L...1F
880:10.1144/1354-079309-843
819:10.1144/0016-764904-070
776:10.1144/0016-764903-140
283:, and other craters on
218:University of Edinburgh
1755:Eugene Merle Shoemaker
1632:Late Heavy Bombardment
463:Comet Shoemaker-Levy 9
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70:identified in or near
1776:Traces of Catastrophe
1760:Earth Impact Database
1708:Ralph Belknap Baldwin
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137:to a large elongated
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904:. www.geolsoc.org.uk
868:Petroleum Geoscience
731:Danielson, Stentor.
289:multi-ringed craters
247:Petroleum Geoscience
1199: /
937:2003LPI....34.1351A
811:2005JGSoc.162..217T
768:2004JGSoc.161..593S
688:10.1038/nature02476
680:2004Natur.428.....U
635:2005GSAB..117..354S
572:10.1038/nature00914
564:2002Natur.418..520S
1672:Shock metamorphism
1577:Alvarez hypothesis
1149:Alvarez hypothesis
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1803:Extinction events
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1725:Edward C. T. Chao
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461:The collision of
448:Yucatan Peninsula
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1750:Peter H. Schultz
1713:Daniel Barringer
1622:Impact structure
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1014:. 27 August 2010
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34:Silverpit Crater
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874:(3): 197–216.
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28:
21:
1774:
1745:Graham Ryder
1667:Shatter cone
1657:Philippinite
1506:Saint Martin
1501:Rochechouart
1406:Gosses Bluff
1361:Amelia Creek
1264:Impact event
1184:
1173:
1169:Shiva crater
1064:. Retrieved
1054:
1042:. Retrieved
1038:
1028:
1016:. Retrieved
1011:
1002:
972:
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906:. Retrieved
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504:Impact event
492:BP Structure
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287:. Normally,
269:
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143:river valley
128:
121:
108:
84:
65:
40:
38:
1541:Tookoonooka
1526:Steen River
1516:Siljan Ring
1446:Manicouagan
1431:Keurusselkä
1206: /
908:27 December
739:27 December
1792:Categories
1682:Stishovite
1582:Australite
1561:Yarrabubba
1531:Strangways
1491:Presqu'île
1466:Montagnais
1436:Lappajärvi
1386:Charlevoix
1371:Beaverhead
1366:Araguainha
1320:By country
1290:Antarctica
1066:16 January
1044:16 January
1018:16 January
847:. BBC News
527:References
498:Doggerland
471:gas giants
393:Cretaceous
374:Cretaceous
275:crater on
139:depression
131:Silver Pit
76:Cretaceous
53:Silver Pit
1647:Moldavite
1642:Meteorite
1627:Impactite
1556:Woodleigh
1551:Vredefort
1511:Shoemaker
1471:Morokweng
1456:Mistastin
1396:Chicxulub
1300:Australia
1280:Worldwide
1165:(primary)
1147:Proposed
888:129267272
827:129927371
784:130073327
456:latitudes
452:dinosaurs
388:Paleogene
342:Chicxulub
258:Structure
235:Zechstein
214:geologist
184:Volcanism
135:fishermen
126:in 2002.
97:Discovery
45:North Sea
1701:Research
1546:Tunnunik
1441:Logancha
1411:Haughton
1381:Carswell
1325:Possible
1012:BBC News
996:Abstract
931:: 1351.
851:30 March
696:15029895
580:12152076
486:See also
437:Callisto
435:'s moon
409:tektites
381:Jurassic
361:tsunamis
281:Callisto
279:'s moon
273:Valhalla
193:Triassic
188:magnetic
151:sediment
1692:Tektite
1687:Suevite
1592:Coesite
1587:Breccia
1536:Sudbury
1486:Popigai
1481:Obolon'
1461:Mjølnir
1426:Karakul
1416:Kamensk
1376:Boltysh
1356:Acraman
1191:54°14′N
1151:craters
987:Bibcode
933:Bibcode
807:Bibcode
764:Bibcode
704:1110093
676:Bibcode
631:Bibcode
588:4381323
560:Bibcode
441:craters
433:Jupiter
277:Jupiter
222:Permian
216:at the
197:Permian
147:Ice Age
118:estuary
111:seismic
57:seismic
1570:Topics
1451:Manson
1305:Europe
1285:Africa
1194:1°51′E
975:: L1.
886:
825:
782:
702:
694:
667:Nature
586:
578:
551:Nature
479:bolide
467:planet
397:Eocene
320:Impact
294:oceans
285:Europa
166:Origin
123:Nature
115:Humber
80:Eocene
1273:Lists
977:arXiv
929:XXXIV
884:S2CID
823:S2CID
780:S2CID
700:S2CID
584:S2CID
384:shale
377:chalk
335:comet
314:chalk
302:water
1421:Kara
1068:2023
1046:2023
1020:2023
910:2009
853:2007
741:2009
692:PMID
576:PMID
402:The
379:and
298:seas
296:and
212:, a
195:and
973:342
876:doi
815:doi
803:162
772:doi
760:161
684:doi
672:428
639:doi
627:117
568:doi
556:418
431:on
399:).
367:Age
82:).
1794::
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395:–
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570::
562::
354:Ă—
350:Ă—
331:Ă—
327:Ă—
78:–
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