66 million years ago, the asteroid produced a global tsunami. Here’s how it spread

At the end of the Cretaceous period, some 66 million years ago, an asteroid impact near the Yucatan Peninsula would have produced a global tsunami 30,000 times more energetic than any modern earthquake-induced tsunami, according to a study pointing to the formation of gigantic waves. .

An asteroid about fourteen kilometers in diameter was involved in the Cretaceous / Paleogene mass extinction about 66 million years ago. The impact caused global temperature fluctuations, large plumes of aerosols, soot and dust, and fires caused by waste materials re-entering the atmosphere. We also know that the impact generated a huge tsunami. On this last point, however, the previous simulations had so far only been able to describe the “local” effects of this event, within the limits of the Gulf of Mexico.

In a new study published in the journal AGU Advances, researchers at the University of Michigan modeled the global effects of this tsunami generated by an asteroid hitting the Earth at 43,000 km / h.

An almost 5 km high wall of water

The team calculated the initial energy of the tsunami impact and found it was up to par 30,000 times greater to the energy of the notorious 2004 tsunami, generated by an earthquake in the Indian Ocean. The impactor would have hit a granite-rich crust covered with thick sediment and shallow water, carving a crater estimated to be a hundred kilometers wide while ejecting dense clouds of dust and soot into the atmosphere.

About 2.5 minutes after the strike, all the displaced material would push a wall of water away from the impact site, creating a wave of nearly five kilometers which would collapse very quickly with the fall of the ejecta. Ten minutes after the impact, waves nearly 1.5 km high would have traveled about 220 km, radiating in all directions from the impact site.

Less than an hour after the impact, the tsunami would then spread from the Gulf of Mexico into the North Atlantic with waves about ten meters high.

Three hours later, these waves would cross the Central American Seaway, a passage that at the time separated North America from South America and the Pacific. Twenty hours later they would have covered nearly the entire extent of the Pacific and Atlantic Oceans, now knocking on the doors of the Indian Ocean (on both sides), but with much less virulence.

About 48 hours after impact, most of the world’s coasts would have been hit by the waves. However, the regions of the South Atlantic, the Indian Ocean and the present Mediterranean Sea would have been largely spared.

Tsunami disturbance modeled four hours after impact. Credits: Range et al. in AGU Advances, 2022
tsunami waves of asteroids
Tsunami disturbance modeled 24 hours after impact. Credits: Range et al. in AGU Advances, 2022

Traces visible in the sediments

The researchers also supported their computer modeling by studying the geological records of around 100 sites around the world. They looked more specifically at the carrots taken from the “border sections” which are marine sediments deposited just before and immediately after the Chicxulub impact. This survey has model predictions confirmed regarding the trajectory and the power of the tsunami generated by the impact.

Some of the most important geological evidence was found 12,000 km from the crater on New Zealand’s east coast. Scientists have found heavily disturbed sediments there that were previously believed to be the result of local tectonic activity. Indeed, the age and location of these deposits placed them directly in the trajectory of those gigantic waves triggered by the asteroid.

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