Approximate location of the Silverpit crater

The Silverpit crater is a sub-sea structure under the North Sea off the coast of the United Kingdom. The crater-like form was discovered in 2001 during the analysis of seismic data collected during routine exploration for oil, and was initially reported as the UK's first known impact crater. However, alternative origins have subsequently been proposed. It is named after the Silver Pit, a feature recognized by generations of fishermen. Image File history File links LinkFA-star. ... Location of Silverpit crater. ... Location of Silverpit crater. ... The North Sea is a sea of the Atlantic Ocean, located between the coasts of Norway and Denmark in the east, the coast of the British Isles in the west, and the German, Dutch, Belgian and French coasts in the south. ... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the movement of waves through the Earth. ... Oil exploration is the search by petroleum geologists for hydrocarbon deposits beneath the Earths surface. ... Tycho crater on Earths moon. ... The Silver Pit is a long valley in the bed of the North Sea, 45 km = 27 miles east of Spurn Head in England. ...

Its age is thought to be of the order of 65 million years, making its formation roughly coincident with the impact that created the Chicxulub Crater (KT boundary). If Silverpit is indeed an impact crater, this may imply that the Earth was struck at that time by several objects, possibly in a similar event to the collision of Comet Shoemaker-Levy 9 with Jupiter in 1994. Several other impact craters around the world are known to date from roughly the same epoch, lending credence to this theory. Radar topography reveals the 180 kilometer (112 mile) wide ring of the crater (image courtesy NASA/JPL-Caltech) Chicxulub Crater is an ancient impact crater buried underneath the Yucatan peninsula, with its center located approximately underneath the town of Chicxulub, Yucatán, Mexico. ... The Cretaceous-Tertiary (KT) extinction event, also known as the KT boundary (from German: Kreide-Tertiär-Grenzschicht), was a period of massive extinction of species, about 65. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ...

Discovery

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). (Image credit:Phil Allen (PGL) and Simon Stewart (BP))

The crater was discovered during analysis of seismic data collected by petroleum geoscientists Simon Stewart of BP and Philip Allen of Production Geoscience Ltd, for a region 130 km off the Humber estuary, during a routine search for fossil fuel deposits. Allen noticed a set of concentric rings, but did not know what they were, and hung an image of them on the wall of his office, hoping someone else might be able to shed light on the mystery. Stewart, visiting Production Geoscience on an unrelated matter, saw the map and suggested it might be an impact crater. The discovery of the crater and the impact hypothesis were reported in the journal Nature in 2002 ^[1]. Image File history File links Download high resolution version (910x776, 103 KB)Silverpit crater in false colour (red/yellow = shallow, blue/purple = deep). ... Image File history File links Download high resolution version (910x776, 103 KB)Silverpit crater in false colour (red/yellow = shallow, blue/purple = deep). ... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the movement of waves through the Earth. ... This article is about the corporation known as BP. For other uses, see BP (disambiguation). ... km redirects here. ... River Hull tidal barrier. ... Estuaries and coastal waters are among the most productive ecosystems on Earth, providing ecological, economic, cultural, and aesthetic benefits. ... Coal rail cars in Ashtabula, Ohio Fossil Fuels are hydrocarbons, primarily coal, fuel oil or natural gas, formed from the remains of dead plants and animals. ... First title page, November 4, 1869 Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ...

Silverpit is named after the Silver Pit fishing grounds in which it is located. The name is given by fishermen to a large depressed area in the bed of the North Sea, which is thought to be an old river valley made when the sea level was lower in the Ice Age. The Silver Pit is a long valley in the bed of the North Sea, 45 km = 27 miles east of Spurn Head in England. ... Categories: Stub ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...

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 expected number of impact craters would be one. In probability theory the expected value (or mathematical expectation) of a random variable is the sum of the probability of each possible outcome of the experiment multiplied by its payoff (value). Thus, it represents the average amount one expects as the outcome of the random trial when identical odds are...

The crater currently lies below a layer of sediment up to 1,500 m in depth, which forms the bed of the North Sea at a depth of about 40 m. Studies suggest that at the time of the crater's formation, the area was under 50 to 300 m of water.
Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... The metre, or meter (U.S.), is a measure of length. ...

Origin

Scientists generally agree that a bolide impact best explains the origin of Silverpit. However, other mechanisms can lead to the formation of craters, and Silverpit's categorization as an impact crater has been questioned. The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. ...

Evidence in favour of impact origin

Other mechanisms for producing a crater were considered and rejected by Allen and Stewart when they discovered the crater. Volcanism was excluded because there were no magnetic 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 Triassic and Permian 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 difficult to form except through a meteorite impact. This article is about volcanoes in geology. ... For other senses of this word, see magnetism (disambiguation). ... The Triassic is a geologic period that extends from about 251 to 200 Ma (million years ago). ... The Permian is a geologic period that extends from about 299. ...

Evidence for alternative interpretations

Analysis of larger scale, but older seismic data by Professor John Underhill, a geologist at the University of Edinburgh, led to a suggestion that withdrawal of material at depth was in fact a better explanation ^[2]. Underhill found that all layers of rock down to the Permian (with an age of about 250 million years) are synclinically folded, and that sediments of this era at the crater are thinned, suggesting that the crater was forming while Permian sediments were being laid down. A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system (see planetary geology). ... The University of Edinburgh, founded in 1583, is a renowned centre for teaching and research in Edinburgh, Scotland. ... The Permian is a geologic period that extends from about 299. ... In geology, a syncline is a type of fold that involves an upward slope to either side. ...

The existence of the central peak which seemed to strongly support the impact hypothesis was considered by Underhill to be equivocal. He suggested it may have been an artifact of image processing, but subsequent seismic reflection mapping of the crater by Stewart and Allen seemed to confirm its existence^[3], and despite Underhill's work, the scientific consensus still broadly favours the impact hypothesis as of 2005. In natural science and signal processing, an artifact is any perceived distortion or other data error caused by the instrument of observation. ... UPIICSA IPN - Binary image In the broadest sense, image processing is any form of information processing for which both the input and output are images, such as photographs or frames of video. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ...

Structure

Seismic data showing the crater and its concentric ring structure (Image credit:Phil Allen (PGL) and Simon Stewart (BP))

Silverpit is about 2.4 km wide. Unusually for a terrestrial crater, it is surrounded by a set of concentric rings, which extend to about 10 km away from its centre. These rings give the crater a somewhat similar appearance to Valhalla crater on Jupiter's moon Callisto, and other craters on Europa ^[4]. Normally, multi-ringed craters 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, whereas two-thirds of impacting objects will land in oceans and seas, so the results of impacts on water are much less well established than those of impacts on land. Compare the Chesapeake Bay impact crater, probably the most thoroughly studied marine impact zone. Download high resolution version (679x640, 153 KB)Silverpit crater seismic map. ... Download high resolution version (679x640, 153 KB)Silverpit crater seismic map. ... Valhalla crater, on Callisto Valhalla is the largest impact crater on Jupiters moon Callisto. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... This article or section does not cite its references or sources. ... Atmospheric characteristics Atmospheric pressure 1 µPa Oxygen 100% Europa (ew-roe-pÉ™, IPA:  ; Greek Ευρώπη) is a moon of the planet Jupiter. ... Oceans (from Okeanos in Greek) are saline waters that cover almost three quarters (71%) of the surface of the Earth. ... For the three letter acronym, see SEA. Sea as seen from jetty in Frankston, Australia Look up maritime in Wiktionary, the free dictionary. ... The Chesapeake Bay Impact Crater was formed by the impact of an extraterrestrial bolide that hit about 35. ...

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 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 chalk below the surface may have acted as the soft mobile layer ^[5]. The Needles, part of the extensive Southern England Chalk Formation. ...

The impact

From the size of the crater and certain assumptions about the speed of an impacting object, the size of the impactor can be estimated. Impacting objects are generally moving at speeds of the order of 20–50 km/s, and at these speeds an object about 120 m across and with a mass of 2.0×10⁹ kg would be required to form a Silverpit-sized crater, if the object was rocky. If it was a comet then it would have been somewhat larger. kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s-1. ... Category: ... The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. It was assigned to the United States in 1889 and is periodically recertified and traceable to the primary international standard, The Kilogram, held at the Bureau International des Poids et... Comet Hale-Bopp A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail â€” both primarily from the effects of solar radiation upon the comets nucleus, which itself is a minor body composed...

For comparison, the object which struck the Earth at Chicxulub is estimated to have measured approximately 9.6 km across, while the object responsible for the Tunguska event in 1908 is thought to have been a comet or asteroid about 60 m across, with a mass of about 4×10⁸ kg.^[6] Radar topography reveals the 180 kilometer (112 mile) wide ring of the crater (image courtesy NASA/JPL-Caltech) Chicxulub Crater is an ancient impact crater buried underneath the Yucatan peninsula, with its center located approximately underneath the town of Chicxulub, Yucatán, Mexico. ... Trees felled by the Tunguska blast. ...

An object 120 m across smashing into the sea at many kilometres per second would generate enormous tsunamis. Scientists are currently searching for any evidence of large tsunamis in the surrounding areas dating from around that time, but as yet no such evidence has been uncovered. For other meanings of tsunami, see tsunami (disambiguation). ...

Age

The position of the crater within the layers of rock and sediment on the sea floor can be used to constrain its age: sediments laid down before the crater's formation will be disturbed, while those laid down afterwards will not be. Allen and Stewart found that Silverpit was formed in Cretaceous chalk and Jurassic shale, but is covered by an undisturbed layer of Tertiary sediment. The Cretaceous Period ended about 65 million years ago but, on the evidence of nearby boreholes, the lowermost Tertiary sediments appear to be absent. Thus the date of the Silverpit event could be anywhere between 65 and 55 million years before present. The Chicxulub impact, which probably played a major role in the extinction of the dinosaurs, occurred 65 million years ago. The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... The Needles, part of the extensive Southern England Chalk Formation. ... // The image above is believed to be a replaceable fair use image. ... Shale Shale is a fine-grained sedimentary rock whose original constituents were clays or muds. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ...

This method of estimating the age of a formation is somewhat crude, and the result is questioned by Underhill's non-impact hypothesis. Other possible ways of dating the impact include looking for evidence of ejecta material such as tektites, and deposits from the hypothesised tsunami, which might be found anywhere around the North Sea basin, but may have been subjected to repeated glaciations. As well as allowing a more accurate age determination, these lines of investigation would also confirm the impact hypothesis. Two nearby oil exploration wells penetrate the ring system, and cutting samples from these are currently being analysed. A tektite Tektites (from Greek tektos, molten) are natural glass objects, up to a few centimeters in size, which — according to most scientists — have been formed by the impact of large meteorites on Earths surface, although a few researchers favor an origin from the Moon as volcanic ejecta. ... A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ...

Analysis of samples taken directly from the central crater would also assist age determination, but such samples have not yet been taken.

Part of a multiple impact?

Silverpit looks more similar to Valhalla crater on Jupiter's moon Callisto than it does to other terrestrial craters

The estimated age of Silverpit leads to inevitable speculation about whether it is related to the much larger Chicxulub crater and the extinction of the dinosaurs. The age is as yet not accurately known, and so at the moment scientists can only speculate. However, several other large impact craters of around the same age have been discovered, all between latitudes 20°N and 70°N, leading to the hypothesis that the Chicxulub impact may have been only one of several impacts that happened all at the same time. Download high resolution version (1196x714, 370 KB)Valhalla crater on Callisto. ... Download high resolution version (1196x714, 370 KB)Valhalla crater on Callisto. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... This article or section does not cite its references or sources. ... Radar topography reveals the 180 kilometer (112 mile) wide ring of the crater (image courtesy NASA/JPL-Caltech) Chicxulub Crater is an ancient impact crater buried underneath the Yucatan peninsula, with its center located approximately underneath the town of Chicxulub, Yucatán, Mexico. ... Latitude, usually denoted symbolically by the Greek letter φ, gives the location of a place on Earth north or south of the Equator. ...

The collision of Comet Shoemaker-Levy 9 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 should collide with a planet. Comets frequently undergo gravitational interactions with the gas giants, and similar disruptions and collisions are very likely to have occurred in the past. The scenario may have occurred on Earth 65 million years ago. Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ... The eight planets and three dwarf planets of the Solar System. ... The solar systems four gas giants against the Suns limb, to scale A gas giant (sometimes also known as a Jovian planet after the planet Jupiter) is a large planet that is not primarily composed of rock or other solid matter. ...

Evidence for this hypothesis is not yet strong, however, as the ages of the Silverpit crater and other possibly related craters are only known to an accuracy of a few million years.

See also

• Impact event
• Bolide
• Chesapeake Bay impact crater
• Comet Shoemaker-Levy 9

Artists impression of a major impact event. ... The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. ... The Chesapeake Bay Impact Crater was formed by the impact of an extraterrestrial bolide that hit about 35. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ...

References

1. ^ Stewart SA, Allen PJ (2002). "A 20-km-diameter multi-ringed impact structure in the North Sea". Nature 418 (6897): 520-3. PMID 12152076.
   
2. ^ Underhill JR (2004). "Earth science: an alternative origin for the 'Silverpit crater'". Nature 428 (6980): 280. PMID 15029895.
   
3. ^ Stewart, S. A. & Allen, P. J. (2005). "3D seismic reflection mapping of the Silverpit multi-ringed crater, North Sea". Geological Society of America Bulletin 117 (3): 354-368. DOI:10.1130/B25591.1.
   
4. ^ Allen P.J., Stewart S.A. (2003). "Silverpit: the morphology of a terrestrial multi-ringed impact structure". Lunar and Planetary Science XXXIV: 1351.
   
5. ^ Collins G.S., Turtle E.P., Melosh H.J. (2003). "Numerical Simulations of Silverpit Crater Collapse". Impact Cratering: Bridging the Gap Between Modeling and Observations, 18.
   
6. ^ Foschini L. (1999). "A solution for the Tunguska event". Astronomy & Astrophysics 342: L1. Abstract

First title page, November 4, 1869 Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ... First title page, November 4, 1869 Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Astronomy and Astrophysics (abbreviated as A&A in the astronomical literature, or else ) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ...

External links

• National Geographic news
• David Darling's space encyclopaedia
• News item from PGL
• British Geological Society
• Further information from the British Geological Society
• North Sea crater shows its scars (BBC News, 18 March 2005)

Coordinates: 54°14′N 1°51′E The current BBC News logo BBC News and Current Affairs is a major arm of the BBC responsible for the corporations newsgathering and production of news programmes on BBC television, radio and online. ... March 18 is the 77th day of the year in the Gregorian calendar (78th in leap years). ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... Map of Earth showing lines of latitude (horizontally) and longitude (vertically), Eckert VI projection; large version (pdf, 1. ...