About 66 million years ago, a massive asteroid crashed into Earth near the site of the small town of Chicxulub in what is now Mexico. The impact eradicated roughly 75% of the animal and plant species on Earth, including whole groups like non-avian dinosaurs and ammonites. According to new research led by University of Michigan scientists, it also triggered a monstrous tsunami with kilometer-high waves that scoured the ocean floor thousands of kilometers from the impact site. The 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 earthquake tsunami; it 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.
At the end of the Cretaceous period, about 66 million years ago, the Chicxulub asteroid impact near the Yucatan peninsula produced a global tsunami 30,000 times more energetic than any modern-day tsunami produced by earthquakes. Image credit: Donald E. Davis / NASA.
“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 Molly Range, a researcher in the Department of Earth and Environmental Sciences at the University of Michigan.
“The review of the geological record focused on boundary sections, marine sediments deposited just before or just after the asteroid impact and the subsequent end-Cretaceous mass extinction.”
“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.”
In their study, Range and her colleagues modeled the first 10 min of the Chicxulub event with a crater impact model, and the subsequent propagation throughout the world oceans using two different global tsunami models.
The impact tsunami was up to 30,000 times more energetic than the December 26, 2004 Indian Ocean tsunami, one of the largest tsunamis in the modern record.
Flow velocities exceeded 20 cm/s along shorelines worldwide, as well as in open-ocean regions in the North Atlantic, equatorial South Atlantic, southern Pacific and the Central American Seaway, and therefore likely scoured the seafloor and disturbed sediments over 10,000 km from the impact origin.
“The big result here is that two global models with differing formulations gave almost identical results, and the geologic data on complete and incomplete sections are consistent with those results,” said Professor Ted Moore, also from the Department of Earth and Environmental Sciences at the University of Michigan.
“The models and the verification data match nicely.”
The team found that 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.
For the study, the researchers did not attempt to estimate the extent of coastal flooding caused by the tsunami.
However, their models indicate that open-ocean wave heights in the Gulf of Mexico would have exceeded 100 m (328 feet), with wave heights of more than 10 m (32.8 feet) as the tsunami approached North Atlantic coastal regions and parts of South America’s Pacific coast.
“The first global simulation of the Chicxulub impact tsunami demonstrates that it was much larger than any recent earthquake-generated tsunami, and that it was likely large enough to leave a mark on marine sediment records,” the scientists said.
“Many uncertainties remain, and there is much room for improvement in future studies.”
Their results were published in the journal AGU Advances.
_____
Molly M. Range et al. The Chicxulub Impact Produced a Powerful Global Tsunami. AGU Advances, published online October 4, 2022; doi: 10.1029/2021AV000627
Source link: https://www.sci.news/paleontology/chicxulub-tsunami-11259.html
