Silverpit crater is a buried sub-sea structure under the North Sea off the coast of the island of Great Britain. The 20 km (12 mi) crater-like form, named after the Silver Pit—a nearby sea-floor valley recognized by generations of fishermen—was discovered during the routine analysis of seismic data collected during exploration for gas in the Southern North Sea Sedimentary Basin. Its origin as a meteor impact structure was first proposed and widely reported in 2002. It would be the first impact crater identified in or near Great Britain. Its age was proposed to lie somewhere in a 29-million-year interval between 74 and 45 million years (Late Cretaceous–Eocene). Other authors have disputed its extraterrestrial origin. An alternative origin was proposed in which the feature was created by withdrawal of rock support by salt mobility, which was overwhelmingly judged to be more plausible in a 2009 debate held by the Geological Society of London. A 2025 paper presented new evidence in favour of an impact origin, suggesting that it was created during the Eocene 46–43 million years ago, with a diameter of approximately 3.2 kilometres (2.0 mi), surrounded by a disturbed zone 18 kilometres (11 mi) in diameter.
Discovery
The crater-like structure was discovered by petroleum geoscientists Simon Stewart and Philip Allen. Analyzing seismic data for a region 130 km (81 mi) off the Humber estuary, 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 Nature in 2002. The structure currently lies below a layer of sediment 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. The Silverpit crater lies near the south of the Dogger Bank in the central North Sea, and it is understood to be named after the Outer Silver Pit and Silver Pit seabed features and fishing grounds to the south and south west of its location. 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.
Origin The origin of the crater is debated by the geoscience community with alternate theories of salt withdrawal and pull-apart basin proposed, raising doubts as to Silverpit's categorization as an impact structure.
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 that Stewart & Allen contend is difficult to form except through a meteorite impact. In 2025, shocked mineral grains were reported from drill cores suggested to represent ejecta from the impact, indicating pressures of 10–13 gigapascals, consistent with an impact origin.
Evidence for alternative interpretations Analysis of regional 2D seismic lines and 3D seismic volumes by John Underhill, a geologist at the University of Edinburgh, 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 Permian (with an age of about 250 million years) are synclinically 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. 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 Zechstein salt. This result was presented at the April 2007 annual meeting of the American Association of Petroleum Geologists 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, Petroleum Geoscience in August 2009 in which he outlined the evidence for an intrusion-related salt withdrawal cause for the feature's formation. 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 alternative genesis through melt-induced salt withdrawal.
Structure
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