Dinosaur-killing asteroid triggered global tsunami with mountain-sized waves

About 66 million years ago, at the end of the Cretaceous period, an asteroid hit Earth in what is now the Gulf of Mexico. The impact would have ejected trillions of tons of dust into the atmosphere, significantly cooling Earth’s climate and leading to the Cretaceous-Paleogene extinction event, a global extinction event responsible for the extinction of about 80 percent of all species on Earth, including the iconic non -Vogel’s dinosaur.

According to computer models released in 2018, the impact also produced a tsunami with waves up to 1.5 kilometers (or nearly 1 mile) high.

In 2021, scientists discovered direct evidence of this tsunami. Seismic images of subsurface layers in Louisiana show fossilized megaripples — sedimentary structures associated with water currents such as occur during a tsunami.

And the monstrous tsunami spread much further from the impact site, according to a new study from the University of Michigan.

“This tsunami was powerful enough to disrupt and erode sediments in ocean basins halfway around the world, leaving either a gap in the sediment record or a jumble of older sediments,” said lead author Molly Range, who conducted the modeling study for a master’s thesis under UM oceanographer and study co-author Brian Arbic; and UM paleoceanographer and study co-author Ted Moore.

The study represents the first global simulation of the Chicxulub impact tsunami to be published in a peer-reviewed scientific journal. In addition, the researchers reviewed the geological record at more than 100 sites worldwide dating back to the Late Cretaceous and found evidence supporting their models’ predictions of the tsunami’s path and magnitude.

“The distribution of erosion and gaps we observed in Upper Cretaceous marine sediments are consistent with our model results, giving us more confidence in the model predictions,” explains Range.

The study authors calculated that the initial energy of the impact tsunami was up to 30,000 times greater than the energy of the December 2004 Indian Ocean tsunami, which killed more than 230,000 people and is one of the largest tsunamis in modern history.

The team’s simulations show that the impact tsunami radiated primarily east and northeast into the North Atlantic and southwest through the Central American Sea Route (which used to separate North America and South America) into the South Pacific.

The researchers modeled an asteroid 14 kilometers in diameter, moving at 12 kilometers per second. It struck a granite crust covered by thick sediment and shallow ocean water, blasted a crater about 100 kilometers wide and ejected dense clouds of soot and dust into the atmosphere.

Two and a half minutes after the asteroid’s impact, a curtain of ejected material pushed a wall of water outward from the impact site, briefly forming a 4.5-kilometer-tall (as tall as the Matterhorn in the Alps) wave that subsided as ejecta fell back to Earth .

According to the simulation, ten minutes after the projectile struck the earth and 220 kilometers from the point of impact, a 1.5-kilometer-high tsunami wave – ring-shaped and spreading outward – began to sweep across the ocean in all directions.

An hour after impact, the tsunami had spread outside the Gulf of Mexico into the North Atlantic.

Four hours after impact, the waves had made their way through the Central American Seaway and into the Pacific.

24 hours after impact, the waves had crossed most of the Pacific from the east and the Atlantic from the west, entering the Indian Ocean from both sides.

Forty-eight hours after impact, tsunami waves more than 10 meters high had reached most of the world’s coasts, likely causing widespread coastal flooding.

“Depending on the geometry of the coast and the waves, most of the coastal regions would be partially flooded and eroded,” the study concludes.

The paper “The Chicxulub Impact Produced a Powerful Global Tsunami” was published in AGU progress (2022). Material provided by the University of Michigan.