For decades, scientists have theorized that a massive impact caused the Cretaceous-Paleogene extinction event. This event occurred about 66 million years ago and caused the mass extinction of about 75% of all plant and animal species on Earth (including the non-avian dinosaurs). With the discovery of the massive Chicxulub crater in the Yucatan Peninsula (southern Mexico) in the 1970s, scientists concluded that they’d found the impact responsible. Based on all the available data, the Chicxulub Impact event is believed to have been as powerful as 100,000 billion metric tons (110,231 U.S tons) of TNT.
This blast was more powerful than all the nuclear devices in the world combined and sent an estimated 25 trillion metric tons (~27.5 US tons) of hot dust, ash, and steam into the atmosphere, creating a global winter. But according to new research led by the University of Michigan, an international team of geologists has determined that the impact also created a global tsunami. According to their findings, this tsunami was 30,000 times more powerful than the 2004 Indian Ocean tsunami, one of the largest and most devastating tsunamis on record.
The team was by Molly M. Range, a with the Department of Earth and Environmental Sciences at the University of Michigan, Ann Arbor. She was joined by an international team of researchers from the NOAA’s Pacific Marine Environmental Lab (PMEL) and Geophysical Fluid Dynamics Laboratory (GFDL), the Institute of Environmental Geosciences (IGE), the Geophysics and Spatial Oceanography Studies Laboratory (LEGOS), the University Corporation for Atmospheric Research (UCAR), the PALEOMAP Project, and multiple universities.
To recap, evidence of the Chicxulub Impact is traced to the crater buried beneath the Yucatan Peninsula of southern Mexico. The crater measures 180 km (110 mi) in diameter and 20 km (12 mi) in depth and is centered offshore near the community of Chicxulub (from which it takes its name). Based on the crater’s dimensions, scientists estimate that the meteor that caused it measured about 14 km (8.7 mi) in diameter. Evidence of the impact is also found in the geological record in the form of deposits of iridium and other impact ejecta that were globally distributed.
This led to the scientific consensus that the impact that led to the Chicxulub crater was responsible for the Cretaceous-Paleogene extinction and possibly the volcanic activity that created the Deccan flood basalt in India. For the sake of their study, Range and her colleagues sought to determine the effects this impact had on the world’s oceans, from the initial moment of contact to the point where it became a global tsunami. To do this, the team created the first global simulation of this impact using hydrocode (which models fluid systems in 3D) and a shallow-water ocean model.
As study co-author Brian Arbic – a researcher with the University of Michigan (Ann Arbor), the IGE, and LEGO – told Universe Today via email, the simulation involved three steps. In the first step, the hydrocode was run by co-author Brandon Johnson (Purdue University) and simulated the first ten minutes of the impact. During this time, explained Arbic, the effects were nothing short of cataclysmic:
“[M]aterial from the asteroid, the underlying bedrock of the Earth, sediment, and ocean was displaced tens of kilometers above the atmosphere and (in the other direction) tens of kilometers below the Earth’s surface – in other words, a great big hole was dug out of the Earth. A massive crater was created by this impact, as well as an outward propagating “rim wave”. Most of the energy in the tsunami is due to the rim wave, but there is also a significant secondary effect due to water rushing back into the crater that the impact created.”
The second step was performed by Range as part of her Master’s Thesis at the University of Michigan, Ann Arbor. This consisted of putting the output of the hydrocode into two global shallow-water tsunami propagation models. These included the Modular Ocean Model 6 (MOM6), developed by co-author Alistair J. Adcroft (a research oceanographer from Princeton University), and the Method of Splitting Tsunami (MOST) developed by co-author Vasily Titov – a senior tsunami modeler at the NOAA’s Pacific Marine Environmental Lab.
“Vasily simulated the tsunami with MOST, and the results are fairly similar to those obtained with MOM6,” said Arbic. “Obtaining similar results from two different models gave us more confidence in our results. We will examine differences between shallow-water models and other models in future work.”
The third step consisted of co-author Ted Moore – a Professor Emeritus at the University of Michigan, Ann Arbor – examining the geological record of the Cretaceous-Paleogene boundary for signs of sediment erosion. This revealed that more erosion occurred in the North Atlantic and South Pacific basins than in the South Atlantic and North Pacific. In short, the geological record shows that the seafloor in these regions was eroded and scoured more aggressively, with flow velocities of about 100 meters per second (360 km/h; 224 mph).
Moreover, the model showed that the wavefront propagation velocities, the speed at which waves formed on the surface, were about 200 meters per second (720 km/h; 447 mph). This is consistent with what the team’s model predicted and constitutes the best observational evidence of a global tsunami at the Cretaceous-Paleogene boundary. Their results also indicate that the Cretaceous-Paleogene tsunami was several orders of magnitude more powerful than any observed in recorded history. As Range described it, the effects of the impact were seen worldwide:
“It was a global impact. The tsunami was seen across the globe in 48 hours. Most coastal regions saw waves hit the coastline. Depending on where you look, wave heights could be from 1 meter to hundreds of meters tall. At ten minutes post-impact, the wave that had formed in the Gulf of Mexico was 1.5 km tall. This tsunami has 30,000 times the energy of the 2004 Indian Ocean Tsunami.”
This research provides additional insight into one of the most important events in geological history. In addition, said Range, the research has significant implications for planetary defense:
“The Chicxulub event had many important impacts, which have been previously documented – fires, wild swings of temperature (both very hot and very cold), destruction and eventual resetting of the predominant forms of life on Earth, and more. The tsunami was another important impact, and we plan to continue studying this tsunami and its impacts on the geological record that we can still examine. Impacts from large asteroids and meteors could happen again, which is why NASA recently ran the DART mission to see if they could be deflected.”
The paper that describes their findings, titled “The Chicxulub Impact Produced a Powerful Global Tsunami,” recently appeared in the journal AGU Advances.
Further Reading: AGU Advances
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