Can a 3.2-kilometre-wide scar under the North Sea rewrite part of Britain’s geology? More than two decades of argument have come to an end with new seismic imaging, microscopic rock examination, and impact simulations all pointing to a clear verdict: the Silverpit structure, hidden 700 metres deep beneath the seabed and 80 miles off Yorkshire, was the result of a hypervelocity asteroid or comet impact about 43 million years ago.
The discovery was made using high-resolution, pre-stack depth migrated 3D seismic data from the Northern Endurance Partnership. This technology, providing full-fold coverage and increased frequency bandwidth, imaged the crater architecture with unprecedented resolution. The images depict sharply defined central uplift, approximately 200 metres high, flanked by concentric faults trending through Paleogene and Cretaceous strata, characteristics that are similar to known marine-target impact craters. “Getting the proof was definitely an exciting moment” said Uisdean Nicholson, the Heriot-Watt University sedimentologist who directed the research. He characterized the hunt as “a needle in the haystack approach.”
The morphology of the crater is textbook for a complicated impact structure within marine sediments: a nested central basin 1.2 km in diameter, a principal rim at 3.2 km, and an 18 km brim of surrounding deformation. Numerical modeling, with the iSALE shock physics code, best correlated with observations for an asteroid of approximately 160 meters in diameter, at a speed of 15 km/s and impacting in water around 100 meters deep. The modeled impact produced shock pressures of up to 30 gigapascals in the chalk bedrock, removed a 1 km-deep transient cavity in 12 seconds, and released a 100-metre-high tsunami.
Microscopic examination of well 43/25-1 drill cuttings just outside the rim produced the smoking gun: shocked quartz and potassium feldspar grains with planar deformation features. Microstructures like these can only be produced at the extreme pressures of an extraterrestrial impact and cannot be mimicked by volcanic, tectonic, or salt movement processes. Biostratigraphic dating of the calcareous nannofossils from the same interval dated the event to the middle Eocene, between 43.06 and 45.95 million years ago.
The seismic data also recorded exceptional secondary features. Small, circular pits up to 150 metres diameter, representing secondary craters from ballistic ejecta, punctuate the brim zone. Within the rim, faint scarps indicate where water cascaded back into the cavity, eroding the crater floor. The modeling indicates these resurges, and following seiching in the shallow basin, reworked ejecta deposits hours after impact, dispersing shocked minerals even into the “forbidden zone” uprange of the oblique strike.
Obliquity is another major conclusion. The curved radial faults within the central uplift and the asymmetric faulting patterns in overlying sediments suggest that the asteroid came in from the west-northwest at a shallow angle. This course of arrival is supported by the ~300-metre offset between the geometric centre of the crater floor and the more deeply exposed central uplift, and the asymmetries in deformation observed in other marine craters like Nadir.
Most interestingly, there is evidence of carbonate devolatilization in the buried chalk. The top 100–200 metres of this unit would have been heated to more than 750°C, leading to thermal decomposition of calcium carbonate to lime and CO₂ gas. Estimated volume loss of as much as 2.2 cubic kilometres correlates with pitted texture seen in seismic images. Such degassing would have forced explosive “secondary ejecta plumes,” a mechanism also proposed for Martian pitted terrains.
The Silverpit crater’s preservation is outstanding. Of about 200 established terrestrial impact structures, a mere 33 are marine, and few have such well-preserved morphology beneath the seafloor. Most are obliterated by erosion, sedimentation, or tectonics. In this case, burial under overlying younger sediments in the tectonically stable southern North Sea has fixed in position the patterns of deformation, offering a scant analogue for how intermediate-sized asteroids interact with shallow marine shelves.
For planetary geologists, the discovery is a reminder that even small impactors of a few hundred metres are capable of having profound geological and environmental impacts. For hazard analysts, it provides a case study in the mechanics of oceanic impacts, from transient crater collapse to tsunami generation. And for Britain, it is the sole verified impact crater in its area, a secret legacy of an Eocene day when a deep space object reconfigured the seafloor in an instant.
