When the asteroid linked to the disappearance of the dinosaurs struck about 66 million years ago, its impacts were dramatic. Indeed, in addition to spitting ash and soot into the atmosphere, it also triggered a wave of some of the world’s worst tsunamis.
A new paper Posted in Advances AGU turns to a combination of computer simulations and marine sediments to fully demonstrate the power and path of these tsunamis for the first time. According to the article, the waves were far more powerful and far more widespread than any in recent memory, radiating all over the world’s oceans.
Although the theory that an asteroid collision contributed to the dinosaurs’ demise was largely ignored when it was first proposed in 1980, a flood of subsequent discoveries quickly made the theory hard to dismiss. Indeed, in addition to the identification of a massive 66 million year old crater along the coast of Mexico’s Yucatán Peninsula, the discovery of important tsunami beds in nearby seas seemed to solidify the theory in the minds of most scientists.
Read more: Did volcanic eruptions drive dinosaurs to extinction?
But, despite these indications that substantial tsunamis accompanied the asteroid, scientists have long struggled to determine just how destructive these waves were.
Using computer simulations, along with sediment samples from around 120 geologic sites across the world’s oceans, a team of scientists finally determined the power and plotted the path of these tsunamis. Involving up to 30,000 times more energy in their initial impact than the worst tsunamis in modern memorythe team says the waves were felt thousands and thousands of miles from the site of the asteroid’s collision.
“This tsunami was powerful enough to disrupt and erode sediment in ocean basins halfway around the world, leaving either a gap in the sedimentary record or a jumble of older sediment,” says Molly Range, author of the study and oceanographer at university. of Michigan, in a Press release.
Simulations and sediments
The team first created a computer simulation of the impact and its immediate aftermath, including the creation of the impact crater and the onset and spread of subsequent tsunamis. Building the simulation on previous scholarship on the asteroid, the team programmed the simulation to assume that the rock was nearly nine miles in diameter and moving at a speed of almost eight miles per second.
According to the simulation, a 62-mile-wide impact crater appeared as soon as the asteroid struck. After two to three minutes, a short-lived three-mile-high wave appeared near the impact site, and after ten minutes a longer-lived, one-mile-high wave appeared, beginning to sweep across the ocean in all directions. .
Even the energy involved in the second of these two waves was far greater than that of many modern tsunamis, manifesting as a ring-shaped wall of water moving outward. Within an hour, the waves had radiated northeast into the North Atlantic. Within four hours, they had also spread southwest into the South Pacific, traveling across the Central American Seaway which connected the Atlantic and Pacific oceans millions of years ago.
These two areas, according to the team, took the brunt of the damage. In addition to creating walls of water on the surface of these oceans, tsunamis also created violent undercurrents in the North Atlantic and South Pacific that were strong enough to erode sediment from the sea floor.
The simulation indicates that within 24 hours of impact, the tsunamis had crossed the majority of the Atlantic and Pacific Oceans and arrived in the Indian Ocean. In less than 48 hours, these waves of tsunamis crashed against most of the coasts of the world.
“Depending on the geometry of the coast and the progression of the waves, most coastal regions would be flooded and eroded to some degree,” the study authors say according to a press release. “All historically documented tsunamis pale in comparison to such global impact.”
The team then studied seafloor sediments from around 120 geological sites around the world to confirm the results of their simulation. Focusing on the so-called “boundary sections” where sediments were deposited at the time of impact, their study revealed significant breaks and disturbances in the sediments of the North Atlantic and South Pacific oceans. This reinforced the conclusions of the simulation on the strength and path of tsunamis.
“Marine sediments are consistent with our model results, giving us more confidence in the model’s predictions,” Range said in a press release.
According to the study authors, the destroyed sediments on the coasts of the New Zealand islands are of particular interest, as they are more than 7,500 miles from the site of the initial impact of the asteroid.
“We believe these deposits record the effects of the tsunami impact, and this is perhaps the most telling confirmation of the global significance of this event,” Range concludes in a press release.