The asteroid that (probably) wiped out the dinosaurs released more than 30,000 times the energy of the deadly 2004 Boxing Day tsunami, a new study has found.
Researchers simulated not just the impact itself but also the ensuing tsunami, then went looking in the real-world places where the kilometres-high wave would have gone, and found evidence backing up what the computer found.
Firstly, Brandon Johnson of Purdue University – home to the classic Impact Earth calculator – modelled the impact. The 14 km-wide asteroid, travelling at 12km/s, hit modern-day Mexico 66 million years ago.
“Two and a half minutes after the asteroid struck, a curtain of ejected material pushed a wall of water outward from the impact site, briefly forming a 4.5km-high wave that subsided as the ejecta fell back to Earth,” the University of Michigan – which led the study – said in a release.
“Ten minutes after the projectile hit the Yucatan, and 220km from the point of impact, a 1.5km-high tsunami wave… began sweeping across the ocean in all directions.”
The second simulation, using a model used in modern tsunami forecasting, took over at the 10-minute mark.
After one hour, the tsunami “had spread outside the Gulf of Mexico and into the North Atlantic”. After four hours, it was into the Pacific.
“Twenty-four hours after impact, the waves had crossed most of the Pacific from the east and most of the Atlantic from the west and entered the Indian Ocean from both sides.”
After two days, most of the world’s coastlines had been hit.
“Any historically documented tsunamis pale in comparison with such global impact,” the researchers said.
While some regions were largely spared the effects of the tsunami (but not the other devastating effects), evidence for the ancient tsunami was found at dozens of sites around the globe.
The most important proof was found on the eastern shores of New Zealand, more than 12,000km away. It was previously thought the “heavily disturbed and incomplete New Zealand sediments, called olistostromal deposits” were the result of local seismic and tectonic activity – but their age and position right in the path of the 66 million-year-old tsunami suggests otherwise.
“We feel these deposits are recording the effects of the impact tsunami, and this is perhaps the most telling confirmation of the global significance of this event,” said lead author Molly Range.The study was published this week in AGU Advances.