Dinosaur-killing asteroid splashed mile-high tsunamis that swept across the globe

Credit: NASA/Don Davis.

The asteroid that hit Earth off Mexico’s Yucatan Peninsula quite simply devastated all life on Earth, not just dinosaurs. The cosmic impact unleashed the force of 10 billion Hiroshima A-bombs and ejected gigatons of sulfur and carbon dioxide into the atmosphere, which could have lowered air temperatures on the surface of a staggering 26 degrees Celsius (47 degrees Fahrenheit). This global winter has lasted for years, long enough to devastate plant life and everything else in the food chain. About 75% of all animal and plant species have disappeared, including the iconic dinosaurs (excluding birds).

But it wasn’t just the explosion and subsequent famine that took its toll. Immediately after the cosmic impact, a monstrous tsunami was triggered. Its waves rose up to a mile and ravaged the ocean floor several thousand miles from the impact site. In a new study, scientists conducted the world’s first simulation of the Chicxulub tsunami, which reveals new insights into the path and power of these huge waves.

“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 from the University of Michigan, who conducted the research. as part of the master’s thesis.

The ripples of an ancient giant tsunami

Range and colleagues, including physical oceanographer Brian Arbic and paleooceanographer Ted Moore, combed through the geological records of more than 100 sites around the world. Specifically, they looked at the K-Pg boundary, a thin layer of sediment deposited just after the asteroid impact that marks the end of the Cretaceous and is around 66 million years old.

These sites showed disturbances in Late Cretaceous marine sediments that are consistent with the researchers’ simulation results, providing assurance that the model is a good approximation of the chain of events that unfolded at the following the asteroid impact. Based on previous studies, researchers estimated that the killer asteroid was about 14 kilometers in diameter (8.7 miles) and struck the Yucatan granitic crust at 43,500 km/h (27,000 mph), forming a massive 100-kilometre-wide (62-mile-wide) crater.

Modeled disturbance of the sea surface height of the tsunami, in meters, 24 hours after the asteroid impact. Credit: Range et al. in AGU Advances, 2022.

Researchers estimated that the energy of the tsunami’s initial impact was up to 30,000 times greater than that of the tsunami from the 2004 Indian Ocean earthquake, one of the deadliest disasters in the world. modern history. The Indian Ocean tsunami struck the coasts of several countries in South and Southeast Asia, killing more than 230,000 people and displacing millions. The 2004 9.1 earthquake ruptured a 900-mile stretch of fault line where the Indian and Australian tectonic plates meet, triggering waves 30 meters high. It’s totally devastating, but now imagine the destruction caused by the Chicxulub tsunami, whose waves reached 1,600 meters high just ten minutes after the projectile hit and up to 4,500 meters high two and a half minutes after the impact.

From the Yucatan Peninsula, the tsunami radiated primarily east and northeast, causing the most damage in the North Atlantic Ocean, as well as southwest through the Central American Seaway, that separated North and South America in the south. Pacific Ocean. The South Atlantic, North Pacific, Indian Ocean and the region that is now the Mediterranean were largely spared the strongest waves of the tsunami.

An hour after impact, the tsunami was already spreading across the North Atlantic. Twenty-four hours later, the waves had crossed most of the Pacific from the east and most of the Atlantic from the west. After 48 hours, the tsunami had reached virtually all the coasts of the Upper Cretaceous world. For example, researchers have identified heavily disturbed marine sediments in New Zealand more than 12,000 kilometers (7,500 miles) from the Yucatan impact site. These sedimentary depositional disturbances were previously thought to be caused by tectonic activity, but their age and location on the path of the modeled Chicxulub impact tsunami suggests a different origin.

“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.

“Depending on coastal geometries and wave progression, most coastal regions would be flooded and eroded to some degree,” the study authors said. “All historically documented tsunamis pale in comparison to such global impact.”

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