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

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When a city-sized asteroid slammed into Earth 66 million years ago, it wiped out the dinosaurs – and sent a monster tsunami rippling around the planet, according to new research.

The asteroid, about 8.7 miles (14 kilometers) wide, left an impact crater about 62 miles (100 kilometers) in diameter near Mexico’s Yucatan Peninsula. In addition to ending the reign of the dinosaurs, the direct hit triggered a mass extinction of 75% of animal and plant life on the planet.

When the asteroid hit, it created a series of cataclysmic events. Global temperatures have fluctuated; plumes of aerosols, soot and dust filled the air; and wildfires started when flaming pieces of material blown up by the impact re-entered the atmosphere and rained down. In less than 48 hours, a tsunami had circled the globe – and it was thousands of times more energetic than modern tsunamis caused by earthquakes.

Researchers set out to better understand the tsunami and its scope through modeling. They 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 American Geophysical Union Advances.

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.

The tsunami was powerful enough to create towering waves more than a mile high and scour the ocean floor thousands of miles from where the asteroid hit, the study found. This effectively 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 on 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.

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 included the size of the asteroid and its speed, which was estimated 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 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 mile high began crossing the ocean in all directions from a point 137 miles (220 kilometers) from impact. .

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

Both models provided almost exactly the same results, creating a tsunami timeline for the research team.

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

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

In less than 24 hours, the waves entered the Indian Ocean from both sides after crossing the Pacific and Atlantic oceans. And 48 hours after the impact, large tsunami waves had 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 strong enough to blow up sediment on the bottom of the ocean.

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

The team analyzed information from 120 sediments largely drawn from previous scientific ocean drilling projects. There were more intact sediment layers in the waters protected from the wrath of the tsunami. Meanwhile, there were gaps in sediment records for 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 with multiple gaps. Initially, scientists thought this was due to the activity of tectonic plates.

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

“We believe these deposits record the effects of the tsunami impact, and this is perhaps the most telling 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 affected by waves of over 32.8 feet (20 meters). The waves only grew as they approached the shore, causing flooding and erosion.

Future research will model the extent of global flooding after impact and how far inland tsunami effects could be felt, according to study co-author and University of Michigan professor. and physical oceanographer Brian Arbic.

“Obviously the biggest floods would have been closest to the impact site, but even far away the waves were likely to be very large,” Arbic said.

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