The asteroid that killed the dinosaurs caused a huge tsunami

The asteroid that killed the dinosaurs caused a huge tsunami

(CNN) — When a city-sized asteroid slammed into Earth 66 million years ago, it wiped out the dinosaurs and produced a monstrous tsunami that swept across the planet, according to new research.

The asteroid, about 14 kilometers wide, left a crater about 100 kilometers in diameter near the Yucatan Peninsula in Mexico. In addition to ending the reign of the dinosaurs, the direct impact caused a mass extinction of 75% of animal and plant life on the planet.

This model shows the maximum amplitude of the tsunami wave after the asteroid impact 66 million years ago. Credit: De Range et al

When the asteroid hit, it created a series of cataclysmic events. Global temperatures fluctuated, plumes of aerosols, soot and dust filled the air and wildfires ignited as pieces of burning material ejected by the impact re-entered the atmosphere and ignited. enjoyed. Within 48 hours, a tsunami had circled the globe and was thousands of times more energetic than modern tsunamis caused by earthquakes.

The researchers set out to better understand the tsunami and its extent through modeling and found evidence to support their conclusions about the tsunami’s path and power by studying 120 ocean sediment cores from around the world. A study detailing the findings was published Tuesday in the journal The American Geophysical Union is progressing.

It is the first global simulation of the tsunami caused by the Chicxulub impact to be published in a peer-reviewed scientific journal, according to the authors.

According to the study, the tsunami was powerful enough to create waves more than a mile high and devastate the ocean floor thousands of miles from where the asteroid struck. In fact, it erased the sedimentary records of what happened before the event, as well as during it.

“This tsunami was powerful enough to disrupt and erode sediment in ocean basins halfway around the world, leaving either a gap in the sedimentary record or a jumble of older sediment,” said lead author Molly. Range, who started working in the study as an undergraduate student. student and completed it for her master’s thesis at the University of Michigan.

Researchers estimate the tsunami was up to 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 that of the volcanic eruption in Tonga earlier this year.

Tracing the path of an ancient tsunami

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

He understood the size of the asteroid and its speed, which was estimated at 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 from the impact, creating a wave 4.5 kilometers high, according to the simulation. This wave subsided when the exploded material fell back to Earth.

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

Ten minutes after impact, a ring-shaped wave about a kilometer high began crossing the ocean in all directions from a point 220 kilometers from impact.

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This graph shows the movement of the sea surface height of the tsunami four hours after the asteroid impact. Credit: De Range et al

This simulation was fed into two different global tsunami models, MOM6 and MOST. While MOM6 is used to model deep sea tsunamis, MOST is part of the National Oceanic and Atmospheric Administration (NOAA) Tsunami Warning Center tsunami forecasts.

Both models gave nearly the same results, creating a tsunami timeline for the research team.

Within an hour of impact, the tsunami had moved past the Gulf of Mexico into the North Atlantic Ocean. Four hours after impact, the waves passed through the Central American Channel and reached the Pacific Ocean. The Central America Channel once separated North and South America.

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This graph shows the movement of the sea surface height of the tsunami 24 hours after impact. Credit: De Range et al

In less than 24 hours, the waves entered the Indian Ocean from both sides after crossing the Pacific and Atlantic oceans. And within 48 hours of impact, large tsunami waves had reached most of the Earth’s coasts.

A changing ocean floor

The undercurrent was strongest in the North Atlantic Ocean, the Central American Sea, and the South Pacific Ocean, exceeding 643 meters per hour, which is strong enough to drag sediment from the ocean floor .

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

The team analyzed information from 120 sediments, mostly from previous scientific ocean drilling projects. There were more layers of intact sediment in the waters protected from the wrath of the tsunami.

But gaps have also been found in the sedimentary record of the North Atlantic and South Pacific oceans.

The researchers were surprised to find that the sediments on the eastern shores of New Zealand’s North and South Islands had been heavily disturbed by multiple lagoons. Initially, scientists thought this was due to plate tectonic activity.

But the new model shows that the sediments lie directly in the path of the Chicxulub tsunami, despite being 12,000 kilometers away.

“We believe these deposits record the effects of the tsunami impact, and this is perhaps the strongest confirmation of the global significance of this event,” Range said.

Although the team did not estimate the impact of the tsunami on coastal flooding, the model shows that coastal regions of the North Atlantic and the Pacific coast of South America were likely hit by waves. more than 20 meters in height. The waves grew as they approached the shore, causing flooding and erosion.

According to study co-author, University of Michigan professor and physical oceanographer Brian Arbic, the extent of global flooding after impact and the distance inland where tsunami effects could have feel will be studied in the future.

“Obviously the greatest flooding would have been near the impact site, but even far away the waves were probably very large,” Arbic said.

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