Silverpit crater is a buried sub-sea structure under the North Sea off the coast of the island of Great Britain. The 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. Discovery The crater-like structure was discovered by petroleum geoscientists Simon Stewart and Philip Allen. Analyzing seismic data for a region 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. Silverpit crater is named after the Silver Pit fishing grounds in which it is located. The name is given by fishermen to a large elongated depression in the bed of the North Sea, which is thought to be an old river valley formed while the sea level was lower during the Ice Age. The structure currently lies below a layer of sediment up to thick, which forms the bed of the North Sea at a depth of about . Stewart and Allen's studies suggest that at the time of its formation, the area was under of water. 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