Here's how a 'monstrous tsunami' killed dinosaurs and changed the world order forever

About 66 million years ago, a miles-wide asteroid hit our planet and led to the Chicxulub impact tsunami that decimated 75 percent of life on Earth. The series of tragedies that resulted from the tsunami are collectively referred to as the Cretaceous- Paleogene (K-Pg) mass extinction event — the day when dinosaurs died for good. For the first time, a team of researchers has created a model that simulates the global propagation of the Chicxulub impact tsunami.

Researchers at the University of Michigan (UM) and Purdue University examined geological data from over 165 locations across the globe. Interestingly, the findings from these sites match with the results demonstrated by their model about the tsunami’s impact. Co-author and associate professor at Purdue University, Brandon Johnson tells IE, “Our simulations of the global propagation of the tsunami show that the tsunami was so large that several meter waves reached most of the world's coastlines.”

Johnson claims that there is almost no comparison between the Chicxulub tsunami and modern tsunamis. For instance, the Chicxulub tsunami had 30,000 times the energy of the 2004 Indian Ocean earthquake-tsunami that caused the deaths of approximately 230,000 people. So, if a tsunami like this happened today, it would devastate coastal populations worldwide.

What does the tsunami impact model suggest?

When geologists examine different sites, they come across sedimentary deposits containing fossils from different ages. Such deposits are often found to be containing remains from different time periods grouped together. In such a case scientists draw a line or boundary between the grouped deposits in order to study them better.

The parts of sedimentary records found exposed on land or recovered in drill cores, where such boundaries can be marked are called 'boundary sections'. To develop their model, the researchers employed advanced computer programs to examine the boundary sections from various sites. Plus, they also went through various earlier studies dealing with the K-Pg extinction.

The scientists' model predicts that 66 million years ago, an 8.7 mile (14 kilometre) wide asteroid hit the Yucatan peninsula in Mexico at a speed of 27,000 miles per hour (12 kilometres per second). The impact from the asteroid resulted in the formation of a crater (Chicxulub) having a diameter of 62 miles (100 kilometers). Soon gigantic clouds of dust covered the surrounding environment.

Within a span of three minutes of the impact, a large amount of material that came out of the crater shook the nearby water bodies, producing waves as high as 2.8 miles (4.5 kilometers). Large ring-shaped tsunami waves began to form at a distance of 137 miles from the Yucatan peninsula after 10 minutes. The model suggests that the waves had so much energy that they were unstoppable and spread in all directions.

After just one hour of the impact, the tsunami’s presence could be strongly felt throughout the North Atlantic Ocean, and in four hours it entered the Pacific. Within 24 hours, the tsunami made its way to the Indian Ocean and a day later, the tsunami waves were wreaking havoc around the globe. “The tsunami was strong enough to erode sediments on the ocean floor halfway around the globe. It is a good thing this impact happened 66 million years ago,” said Professor Johnson.

Why are such models important today?

The K-Pg mass extinction event happened 66 million years ago. However, it is still relevant for studying how a celestial body could trigger a series of cataclysmic events in different corners of Earth. Humanity has not experienced a tsunami of the scale of the one that resulted from the Chicxulub impact. Still, the knowledge of past events could enable us to mitigate the damage from other similar large impacts happening in the future.

Professor Johnson claims that, along with colleagues at Purdue and UM, the team have successfully developed the world's first simulation model of the Chicxulub impact tsunami. However, it is not perfect as there are uncertainties regarding details of the impact and what the continents and ocean basins looked like 66 Myrs ago.

Johnson tells IE, “We are hoping to follow this work up and look into how far the tsunami would go onto land around the globe. We are particularly interested in how far up the Western Interior Seaway, a shallow sea that extended up into North America from the gulf of Mexico, the tsunami would travel.”

The study is published in the journal AGU Advances.