The asteroid that wiped out the dinosaurs also caused a global tsunami

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When a city-sized asteroid hit Earth 66 million years ago, it wiped out the dinosaurs and sent a monster tsunami across the planet, according to new research.

The asteroid, 8.7 miles (14 kilometers) across, left an impact crater about 62 miles (100 kilometers) off Mexico’s Yucatan Peninsula. In addition to ending the reign of the dinosaurs, the direct impact caused the mass extinction of 75% of the planet’s animal and plant life.

When the asteroid hit, it set off a series of cataclysmic events. Global temperatures changed; aerosols, soot and dust plumes filled the air; and fires started as fiery fragments of material exploded on impact re-entered the atmosphere and rained down. Within 48 hours, a tsunami surrounded the world, and it had thousands of times the energy of modern tsunamis caused by earthquakes.

The researchers set out to better understand the tsunami and its reach through modeling. By analyzing 120 ocean sediment cores from around the world, they found evidence to support their findings about the path and strength of the tsunami. A study detailing the findings was published in the American Geophysical Union Advances.

This is the first global simulation of a Chicxulub-induced tsunami to be published in a peer-reviewed scientific journal, according to the authors.

The tsunami was powerful enough to create waves more than a mile high and scour the ocean floor thousands of miles from where the asteroid hit, according to the study. It effectively erased the sedimentary record of what happened before, as well as during, the event.

“This tsunami was powerful enough to mix and erode sediments in ocean basins in the middle of the world, leaving a gap in the sedimentary record or a mix of older sediments,” said lead author Molly Range, who began working on the study as an undergraduate. student and did his master’s thesis at the University of Michigan.

Researchers estimate that the tsunami was 30,000 times more energetic than the December 26, 2004 Indian Ocean tsunami, one of the largest on record, which killed more than 230,000 people. The energy of the asteroid impact was at least 100,000 times greater than the eruption of the Tonga volcano earlier this year.

Brandon Johnson, study author and associate professor at Purdue University, used a large computer program called hydrocode to simulate the first 10 minutes of Chicxulub’s impact, including the creation of the crater and the start of the tsunami.

It included the size of the asteroid and its speed, which was estimated to be moving at 26,843 miles per hour (43,200 kilometers per hour) when it hit the granite crust and shallow waters of the Yucatan Peninsula.

Less than three minutes later, rocks, sediment and other debris pushed a wall of water away from the impact, creating a wave 2.8 miles (4.5 kilometers) high, according to the simulation. This wave subsided as the detonated material returned to Earth.

But as the debris fell, it created even more chaotic waves.

Ten minutes after the impact, a mile-high ring-shaped wave began to sweep across the ocean in all directions from a point 220 kilometers from the impact.

This simulation was then fed into two different global tsunami models, MOM6 and MOST. While MOM6 is used to model deep ocean tsunamis, MOST is part of Tsunami forecasting at the National Oceanic and Atmospheric Administration’s Tsunami Warning Centers.

Both models produced nearly identical results, creating a tsunami timeline for the research team.

An hour after impact, the tsunami traveled beyond the Gulf of Mexico into the North Atlantic. Four hours after the impact, the waves moved through the Central American Seaway and into the Pacific Ocean. The Central American Seaway once separated North America from South America.

This graph shows the movement of the sea surface height of the tsunami 24 hours after the impact.

Within 24 hours, waves entered the Indian Ocean from both sides after crossing the Pacific and Atlantic Oceans. And 48 hours after the impact, huge tsunami waves reached most of the Earth’s coasts.

The undercurrent was strongest in the North Atlantic Ocean, the Central American Seaway, and the South Pacific Ocean, exceeding 0.4 miles per hour (643 meters per hour), which is enough to remove sediment from the ocean floor.

Meanwhile, the Indian Ocean, North Pacific, South Atlantic and Mediterranean were protected from the worst of the tsunami, with smaller undercurrents.

The team analyzed information from 120 sediments from scientific ocean drilling projects. There were much more layers of sediment in the waters that were protected from the wrath of the tsunami. Meanwhile, there were gaps in the North Atlantic and South Pacific sediment record.

The researchers were surprised to find that much of the sediment on the eastern shores of New Zealand’s North and South Islands had been disturbed with multiple voids. At first, scientists thought this was due to the activity of tectonic plates.

But the new model shows that the sediments are directly in the path of the Chicxulub tsunami, despite being 7,500 miles (12,000 kilometers) away.

“We believe that these deposits are recording the effects of the tsunami of the impact, and this is perhaps the most telling confirmation of the global importance of this event,” said Range.

The team did not estimate the impact of the tsunami on coastal flooding, but the model shows that coastal regions of the North Atlantic and the Pacific coast of South America likely experienced waves higher than 32.8 feet (20 meters). The waves grew as they approached the shore, causing flooding and erosion.

Future research will help model the extent of global flooding after the impact and how far the effects of the tsunami might be felt, according to study author Brian Arbic, a professor and physical oceanographer at the University of Michigan.

“It is known that the biggest floods would be closest to the impact site, but even far away the waves would be very big,” said Arbic.