Dinosaur-killing asteroid triggered global tsunami that scoured seafloor thousands of miles from impact site

About three-quarters of the planet's plant and animal species were wiped out by the asteroid that hit 66 million years ago.

According to a new University of Michigan-led study, it triggered a huge wave that scoured the ocean floor thousands of miles from the impact site.

The study will be published in a peer-reviewed journal in October. U-M researchers reviewed the geological record at more than 100 sites around the world and found evidence that supports their models' predictions.

Lead author Molly Range, who conducted the modeling study for a master's thesis under U-M's physical oceanographer, said that the wave was strong enough to cause a gap in the records of the ocean basins.

The asteroid impact and the K-Pg mass extinction were the focus of the review.

The model results are consistent with the distribution of the erosion and hiatuses that we observed, which gives us more confidence in the predictions.

The December 2004 Indian Ocean earthquake tsunami, which killed more than 220,000 people, was one of the largest earthquakes in the modern era.

In those basins and in some adjacent areas, underwater current speeds can reach 20 centimeters per second, which is a speed that is strong enough to cause serious damage to the seafloor.

The current speeds were probably less than the threshold.

Moore was able to get usable information from 120 of the 165 marine boundary sections that he analyzed. The majority of the material came from the ocean-drilling project.

The North Atlantic and South Pacific had the lowest number of sites. The South Atlantic, the North Pacific, the Indian Ocean and the Mediterranean have the largest number of complete K-Pg boundary sections.

The professor of earth and environmental sciences who oversaw the project said that they found corroboration in the geological record. The geological evidence makes the paper stronger.

There are outcrops of the K-Pg boundary on the eastern shores of New Zealand's north and south islands which are close to the impact site.

Olistostromal deposits in New Zealand were thought to be the result of local activity. The U-M-led research team suspects a different origin for the deposits because of their age and their location in the path of the impact.

The most telling confirmation of the global significance of the event is that these deposits are recording the effects.

The study used a two-stage strategy. A computer program called a hydrocode was used to make a simulation of the chaotic first 10 minutes of the event. The work was done by Brandon Johnson.

The researchers modeled an asteroid that was 14 kilometers in diameter, moving at 12 kilometers per second. dense clouds of soot and dust were ejected from the crater, which was 100 kilometers wide and 62 miles long.

Two and a half minutes after the asteroid struck, a curtain of ejected material pushed a wall of water out from the impact site.

A 1.5 kilometer-high (0.9 mile-high) wave swept across the ocean in all directions after the projectile hit the peninsula.

The results of Johnson's hydrocode simulations were entered into two models at the 10-minute mark. In the deep ocean, the MOST model has been used by the National Oceanographic and Atmospheric Administration to forecast the waves.

Moore said that the geologic data on complete and incomplete sections are consistent with the results of the global models. The models and verification data are very similar.

The team's simulation says that way.

• 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.
• By 48 hours after impact, significant tsunami waves had reached most of the world's coastlines.

The researchers didn't try to estimate the extent of coastal flooding caused by the wave.

Their models show that the wave heights in the Gulf of Mexico would have been over 100 meters, with wave heights of more than 10 meters in parts of South America.

The wave heights would have increased as the shorelines were near the water. Current speeds exceed the threshold for most coastal areas.

Most coastal regions would be eroded to some extent depending on the geometries of the coast. It pales in comparison to the global impact of the waves.

Arbic said a follow-up study is planned to model the extent of coastal flooding. The leader of that study will be a co-author of the AGU Advances paper.

More information: The Chicxulub Impact Produced a Powerful Global Tsunami, AGU Advances (2022). agupubs.onlinelibrary.wiley.co … 10.1029/2021AV000627 Journal information: AGU Advances