The asteroid that hit Earth 66 million years ago, destroying three-quarters of the planet's plant and animal life (most notably the dinosaurs), also caused a global tsunami with mile-high waves. New research headed by experts from the University of Michigan finds that the tsunami ravaged the ocean floor and left geologic evidence as far away as New Zealand, thousands of kilometers from the impact location off what is now Mexico's Yucatan Peninsula. The findings come from the first simulation of the worldwide consequences of the large asteroid known as the Chicxulub impactor on Earth to be published. The scientists used earlier study findings to simulate the asteroid as an 8.7-mile-wide (14-kilometer) body traveling at 27,000 mph (43,000 kph).
The computer modeling was supplemented by the researchers' investigation of the geological record at 100 locations throughout the world. The scientists focused on boundary sections, which are marine sediments set down right before and after the Chicxulub impact and the cataclysmic extinction that ended our planet's Cretaceous epoch. This analysis confirmed the model's predictions about the route and intensity of the Chicxulub-generated wave.
Molly Range, the lead author and a graduate student at the University of Michigan at the time of the research, stated that the tsunami was strong enough to disturb and erode sediments in ocean basins halfway around the world, leaving either a gap in the sedimentary records or a jumble of older sediments. The distribution of erosion and hiatuses found in top Cretaceous marine deposits matches our model results, giving us additional confidence in the model predictions.
The researchers discovered some of the most important geological evidence 7,500 miles (12,000 km) distant from the Chicxulub crater on the eastern coastlines of islands to the north and south of New Zealand. The scientists discovered extremely disturbed strata known as olistostromal deposits, which were previously thought to be the product of local tectonic activity. Range and her colleagues discovered, however, that the age and position of these deposits put them precisely in the path of the Chicxulub-triggered tsunami that the researchers projected.
Range stated, "We believe these deposits are recording the effects of the impact tsunami," which is possibly the most compelling proof of the event's worldwide importance.
The initial energy of the impact tsunami was computed and found to be up to 30,000 times larger than the energy of the 2004 tsunami caused by an Indian Ocean earthquake. More than 230,000 people were killed in the disaster, which was one of the greatest tsunamis in contemporary history.
According to the simulation, the Chicxulub-triggered tsunami would have spread to the east and northeast into the North Atlantic, then to the southwest, across the Central American Seaway that divided North and South America at the time, and finally into the South Pacific Ocean. Deep under the ocean's surface, some of the tsunami's most damaging consequences occurred, with the scientists calculating that underwater currents in these and neighboring places reached rates of up to 0.4 mph (0.6 kph). According to the new modeling, other places such as the South Atlantic, North Pacific, Indian Ocean, and the region that is now the Mediterranean were spared the most severe consequences of the tsunami.
The researchers employed a two-stage technique to simulate the asteroid impact and the accompanying wave. The initial phase was to simulate the mayhem that occurred during the first 10 minutes of the Chicxulub impactor hit, including the development of the crater and the start of the tsunami. This simulation indicated that the impactor struck a granite-rich crust coated in thick sediments and shallow water, carving up a crater 60 miles (100 km) wide and ejecting massive clouds of dust and soot into Earth's atmosphere.
The simulation reveals that displaced material would have pushed a wall of water out from the impact site around 2.5 minutes after the collision, generating a wave roughly 3 miles (5 km) high that would have calmed down when debris began to fall back to Earth. Tsunami waves about a mile in height would have traveled roughly 140 miles (220 km) from the impact site, spreading outward in a ring-like structure and sweeping across the oceans in all directions within 10 minutes after impact. After 10 minutes, the team's simulation breaks into two models that compute how the massive waves went further afield; one of these models was utilized by the National Oceanic and Atmospheric Administration (NOAA) to develop tsunami warnings.
The key conclusion here, according to Ted Moore, a paleoceanographer at the University of Michigan, is that two global models with different formulations produced almost equal results, and geologic evidence from full and partial sections is compatible with those results. The models and verification data are very well matched.
The scientists then recreated the ancient disaster's subsequent progression. Within an hour after the tsunami's impact, it had expanded over the Gulf of Mexico and into the North Atlantic; four hours later, the waves had traveled through the Central American Seaway and into the Pacific.
The simulation indicated that 24 hours after the Chicxulub impactor hit Earth, the waves it created had gone practically the entire length of the Pacific and Atlantic Oceans and had just recently entered the Indian Ocean from both sides.
Tsunami waves impacted most of the world's coasts two days after the catastrophe. The scientists did not quantify the amount of flooding produced by the tsunami waves, but they did compute wave heights in the most heavily hit areas. According to the calculations, waves in the open water of the Gulf of Mexico would have been over 330 feet (100 meters) high.
Meanwhile, waves on the North Atlantic coast and sections of South America's Pacific coast would have been 10 times smaller, at roughly 33 feet (10 meters). However, once the tsunami waves reached these shorelines and struck shallow seas, they would have risen considerably in height again.
Most coastal places would be swamped and degraded to some extent, according to the scientists, depending on the geometries of the shore and the approaching waves. Any previously recorded tsunamis pale in contrast to such worldwide devastation.
The team's findings will be published in the journal AGU Advances on Tuesday, October 4.