Cracking a cold case is always tricky. But figuring out one from 43 million years ago is almost impossible. Yet in 2009, a group of scientists tried to do just that. Gathered at the Geological Society of London, scientists were tasked with deciding the origin of a strange, multi-ringed scar sitting under the floor of the North Sea.
Known as the Silverpit Crater, the 3.3 km (2-mile) structure had been debated since its discovery in 2002. Some researchers saw it as the footprint of a cosmic intruder. To others, it was just a messy collapse caused by ancient salt leaking out of the deep earth.
The skeptics won that day in 2009. The vote was overwhelmingly against the asteroid. But a new study says the vote was wrong. By combining high-resolution 3D seismic imaging with the discovery of shocked minerals, an international team of researchers has confirmed that Silverpit was indeed formed by a space rock, and one that made a massive wave when it hit the Earth.
The Shape of a Real Impact
The primary reason Silverpit remained a mystery for so long was because it’s hard to study. The alleged crater is buried deep beneath the seabed of the UK continental shelf. You can’t walk across it or study it. Instead, researchers tried to figure it out using seismic studies.
Seismic surveys work a bit like an underground ultrasound. Ships tow arrays of air guns and long cables packed with sensors behind them, then fire repeated sound pulses into the seabed. Those waves travel down through layers of mud, chalk, and older rock, then bounce back at different speeds depending on what they hit. By measuring those echoes across a tight 3D grid, scientists can rebuild a buried structure in remarkable detail.
In Silverpit’s case, researchers only had bits and pieces of the entire structure. But the newest survey, collected in 2022, produced much sharper images than the older data. Earlier seismic images were good enough to hint that something strange was there, but the newer dataset gave researchers near-complete coverage of the crater and its wider damage zone. You can see the central uplift, ring faults, and crater floor that fit perfectly with an asteroid impact.
But still, the smoking gun was missing.
Minerals Are the Smoking Gun
When an asteroid hits at kilometers per second, the pressure wave is so intense that minerals can develop distinctive microscopic features. These are not the kind of fractures made by ordinary tectonics, salt movement, or volcanic fluids. Researchers led by Dr. Uisdean Nicholson of Heriot-Watt University in Edinburgh managed to find those as well.
They got a bit lucky.
The researchers went back to rock fragments, or “cuttings,” pulled from a deep well drilled by British Gas back in 1985. Hidden in those forty-year-old bags of mud, they found two tiny grains: one quartz and one potassium feldspar. Within these grains were the telltale signs of an asteroid impact.
“We were exceptionally lucky to find these — a real ‘needle-in-a-haystack’ effort. These prove the impact crater hypothesis beyond doubt, because they have a fabric that can only be created by extreme shock pressures,” says Nicholson.
A Bad Day for the Eocene
After researchers figured out it was indeed an asteroid, they moved on to modelling.
The impact happened during a period called the Middle Eocene, when the North Sea was an open, shallow marine environment. The intruder was a rocky asteroid about 160 meters wide — roughly the size of a large football stadium. It didn’t fall straight down. The damage zone and the way the faults are skewed tell a story of a low-angle, oblique impact. The asteroid screamed in from the west-northwest, hitting the water at about 15 kilometers per second.
At that speed, it punched through 100 meters of water and hundreds of meters of sediment, carving out a transient hole a kilometer deep. It landed on a layer-cake of soft clay sitting on top of brittle chalk. This chalk matters a lot.
Chalk is mostly calcium carbonate. When you hit it with enough energy, it decomposes into lime and carbon dioxide gas. The researchers estimate that between 0.9 and 2.2 cubic kilometers of rock simply vanished from the center of the crater. It simply vaporized. As if the impact itself wasn’t bad enough, this triggered a secondary explosion of gas and steam, creating a plume that shot back out of the crater like a cosmic geyser.
The impact would have displaced a massive volume of water, creating a tsunami that eventually roared back toward the hole. This tsunami went up to 100 meters (330 feet). This wasn’t enough to cause a widespread extinction, but it was definitely a bad day for any creature unfortunate enough to be around it.
But for geologists studying it today, this cold case finally has an answer. Thanks to some old bags of mud and modern sensors, we finally know the truth about the ghost in the Silverpit.
The study was published in Nature.