More than 66 million years ago, an asteroid hit Earth, wiping more than three-fourths of plant and animal life on the blue planet, including the dinosaurs. When the asteroid, thought to be more than 10 kilometres in diameter, hit the Earth, the impact matched the level of several million nuclear bombs exploding simultaneously. The place where the collision happened is the modern-day Gulf of Mexico. The impact of the collision also created a dent in the Earth’ surface which is known as the Chicxulub crater. The crater, 200 kilometres wide, lies along the coast of the Yucatan Peninsula, a Mexican territory that separates the Caribbean Sea from the Gulf of Mexico.
The collision also created up to 1.5-kilometre high tsunami waves that were believed to have travelled more than 250 kilometres from their origin. Now, some 1000 kilometres north of the impact site, scientists have found direct evidence of the tsunami for the first time. Using seismic imagery, typically used for hunting subsurface oil and gas reservoirs, scientists found 600-metre long “megaripples” embedded in marine rocks, some 1,500 metres deep. Ripples as tall as 16 metres register the sand deposit caused by the uprush currents as well as impacts of backwash currents.
According to the scientists, these layers in the marine rocks could not have been caused by usualcurrents. Moreover, their orientation matches the direction of tsunami waves produced from the asteroid impact.
Geologists believe that the reason these megaripples are preserved even after millions of years is that they formed below the region where storm waves could cause erosion. Moreover, they were later buried by deep water shales, sedimentary rocks that form in slow-moving water.
The findings were published on July 2 in Earth and Planetary Science Letters.
The tsunami waves were guessed in 2019 by computer simulations of the asteroid impact. The guess was supported by fossil remains found in North Dakota the same year. The fossils of marine animals, probably swept by the tsunami waves, were found some 1,800 metres north of the impact site.