Artist’s impression of an asteroid impact on Earth.
About 66 million years ago, at the end of the Cretaceous period, an asteroid hit Earth in what is today the Gulf of Mexico. The impact would have thrown trillions of tons of dust into the atmosphere, cooling the Earths climate significantly and leading to the Cretaceous–Paleogene extinction, a global extinction event responsible for eliminating approximately 80 percent of all species on Earth.
According to computer models published in 2019, the impact also generated a tsunami with waves up to 1.5 kilometers (or nearly 1 mile) high.
In 2021, scientists discovered direct evidence for this tsunami. Seismic images of underground layers in Louisiana show fossilized megaripples – sedimentary structures associated with water currents as experienced during a tsunami.
And the monstrous tsunami travelled far wider from the impact site, according to a new University of Michigan-led study.
“This tsunami was strong enough to disturb and erode sediments in ocean basins halfway around the globe, leaving either a gap in the sedimentary records or a jumble of older sediments,” said lead author Molly Range, who conducted the modeling study for a master’s thesis under U-M physical oceanographer and study co-author Brian Arbic and U-M paleoceanographer and study co-author Ted Moore.
The study presents 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 to the end-Cretaceous and found evidence that supports their models’ predictions about the tsunami’s path and power.
“The distribution of the erosion and hiatuses that we observed in the uppermost Cretaceous marine sediments are consistent with our model results, which gives us more confidence in the model predictions,” explains Range.
The study authors calculated that the initial energy in the impact tsunami was up to 30,000 times larger than the energy in 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 mainly to the east and northeast into the North Atlantic Ocean, and to the southwest through the Central American Seaway (which used to separate North America and South America) into the South Pacific Ocean.
Maximum tsunami wave amplitude, in centimeters, following the asteroid impact 66 million years ago.
The researchers modeled an asteroid that was 14 kilometers in diameter, moving at 12 kilometers per second. It struck granitic crust overlain by thick sediments and shallow ocean waters, blasting a roughly 100-kilometer-wide crater and ejecting dense clouds of soot and dust into the atmosphere.
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 4.5-kilometer-high (as high as the Matterhorn in the Alps) wave that subsided as the ejecta fell back to Earth.
Ten minutes after the projectile hit Earth and 220 kilometers from the point of impact, a 1.5-kilometer-high tsunami wave—ring-shaped and outward-propagating—began sweeping across the ocean in all directions, according to simulation.
One hour after impact, the tsunami had spread outside the Gulf of Mexico and into the North Atlantic.
Four hours after impact, the waves had passed through the Central American Seaway and 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.
Forty-eight hours after impact, tsunami waves more than 10 meters high had reached most of the world’s coastlines, likely causing widespread coastal flooding.
“Depending on the geometries of the coast and the advancing waves, most coastal regions would be inundated and eroded to some extent,” the study concludes.
The paper “The Chicxulub Impact Produced a Powerful Global Tsunami” is published in AGU Advances (2022). Material provided by the University of Michigan.
