A long-standing scientific debate over the origin of the Silver Pit crater beneath the southern North Sea has finally been resolved.
New research shows that the structure was formed when an asteroid or comet impacted the area approximately 43 to 46 million years ago.
The research was led by Dr Wisdeen Nicholson from Heriot-Watt University in Edinburgh and supported by the Natural Environment Research Council (NERC). The research team combined seismic images, microscopic analysis of rock debris, and computer modeling to produce the clearest evidence yet that Silver Pit is one of Earth’s rare impact craters.
Research published in a magazine nature communications.
Hidden crater under the North Sea
The Silver Pit is located approximately 700 meters below the seabed in the North Sea, approximately 130 miles off the coast of Yorkshire.
Since geologists first identified the formation in 2002, the three-kilometre-wide crater and the 20-kilometre ring of fault surrounding it have sparked intense debate.
Early studies proposed that this feature was formed by a high-velocity asteroid impact. Proponents of this idea pointed to its rounded shape, central peak, and surrounding concentric faults that are common in known impact craters.
Other scientists have proposed other explanations. Some argued that the movement of underground salts caused the rock layers to warp and form the structure. Some argued that volcanic activity may have caused the collapse of the ocean floor.
In 2009, geologists also voted on the issue. At the time, most participants rejected the asteroid impact explanation, according to a report in the December 2009 issue of Geoscientist magazine.
The latest findings overturn that conclusion.
New seismic data reveals evidence of impact
Nicholson’s team analyzed newly available seismic images and geological samples taken from beneath the ocean floor.
Dr Wisdeen Nicholson, a sedimentologist at Heriot-Watt University’s School of Energy, Earth Sciences, Infrastructure and Society, said: ‘The new seismic images provide an unprecedented view of the crater.
“Samples taken from oil wells in the area also revealed rare ‘shocked’ quartz and feldspar crystals at the same depth as the crater floor.
“We were very lucky to find these. It was a real ‘needle in a haystack’ effort. They proved the impact crater hypothesis beyond any doubt, because they have structures that can only be created by extreme impact pressures.”
These microscopic minerals only form under the extreme pressures that occur during an asteroid impact, providing strong support for this event.
Massive tsunami caused by asteroid impact
Evidence shows that the asteroid, about 160 meters wide, hit the ocean floor from the west at a shallow angle.
Dr Nicholson said: “Our evidence shows that a 160m wide asteroid hit the ocean floor at a low angle from the west.
“Within minutes, a 1.5-kilometer-high curtain of rock and water formed, which collapsed into the sea, creating a tsunami over 100 meters high.”
The impact would have caused a violent explosion on the ocean floor, sending huge waves across the area.
The “magic bullet” that put an end to the controversy
Professor Gareth Collins from Imperial College London attended a 2009 debate on the origins of craters and contributed to the numerical simulations used in the new study.
Professor Collins said: “I have always thought that the impact hypothesis is the simplest explanation and the one that is most consistent with observations.
“It’s extremely rewarding to finally have found the silver bullet. With our amazing new data, we can now begin the exciting work of learning more about how impacts shape the planet below the surface, something that is very difficult to do on other planets.”
A rare and well-preserved impact crater
Dr Nicholson said: ‘Silver Pit is a rare and exceptionally preserved hypervelocity impact crater.
“These phenomena are rare because Earth is a very dynamic planet. Plate tectonics and erosion destroy almost all traces of most of these phenomena.
“About 200 impact craters have been found on land, but only about 33 have been found on the ocean floor.
“These discoveries can be used to not only understand how asteroid impacts have shaped our planet throughout history, but also to predict what will happen if there is an asteroid impact in the future.”
Confirmation that Silver Pit is an impact crater puts it in the same category as well-known structures such as Mexico’s Chicxulub crater, which has been linked to the dinosaur mass extinction, and Nadir crater off the coast of West Africa, which was recently identified as another impact site.
This research was funded by the Natural Environment Research Council (NERC).
