The Chicxulub Crater, located below the Gulf of Mexico waters, marks the impact site of an asteroids that hit Earth 66 millions years ago. The fifth mass extinction, which saw the extinction of about 80% all animal species (including non-avian dinosaurs), was the most significant outcome of this cataclysmic catastrophe.
What happened to the asteroid when it collided with Earth's surface?
Scientists have gathered information from the world's geology, Chicxulub included, to reconstruct what happened on that horrible day and in the years that followed.
Related: How long will most species survive before becoming extinct?
According to Nature Communications 2020, the asteroid was already destined for destruction, having collided with Earth at the most dangerous angle. Sean Gulick, a researcher at the University of Texas Institute for Geophysics who led the study, stated that the asteroid measured approximately 7.5 miles (12 km) in diameter. It was travelling at about 27,000 mph (43,000 km/h). The asteroid hit the planet at 60 degrees above the horizon. This angle proved to be particularly dangerous because it allowed the impact of the asteroid to release large amounts of dust and aerosols into our atmosphere.
Gulick cited evidence from his colleague in the area to support the simulations of an angled hit. This included the asymmetrical structure in the crater and the position of upwarped mantle rocks. The unique sediment sequences found in cores taken from the region. And, especially, the lack of a specific type of rock called evaporites in the cores.
Gulick's team estimates that the impact would have vaporized evaporite rock, sending 325 gigatons sulfur (as sulfur aerosols) and 435 gigatons carbon dioxide into the atmosphere.
According to a 2014 study in Nature Geoscience, the material that was thrown into the atmosphere contained mainly pulverized rocks and drops of sulfuric acid. This material came from anhydrite-rich marine rocks. The planet was protected from the sun's rays by this cloud of microscopic material. The planet's climate was drastically affected by the long-term cooling. Geophysical Research Letters published a 2016 study that found that the average temperature of the tropics dropped from 81 F (27 degrees Celsius), to 41 F (5 C). The photosynthesis process slowed down as the incoming sunlight became less intense, and the food chain in land and ocean fell, leading to the death of many animals, including dinosaurs.
The 2014 study revealed that the airborne sulfuric acids caused lethal acid rain to form for several days after the impact. This killed countless marine animals in the oceans and lakes, along with many others.
Also, the impact caused massive tsunamis that propagated through the oceans. According to modeling research, the wave reached almost 1 mile (1 km) in height and traveled 89 miles (143 km/h). Other waves reached great heights, reaching up to 46 feet (15m) in Atlantic Ocean and 13 feet (4m) North Pacific Ocean. The sediment record in Louisiana also contains depositional evidence of the huge waves. 3D seismic surveys of Louisiana's geology revealed mega ripples up to 52 feet (16 m) in length that pointed back to the Gulf impact site.
Fires erupted
Researchers compared the impact to a broiler that ignites dry tinder. Further reducing sunlight incoming, the additional smoke and ash probably contributed to the cooling shroud.
Geologists can easily see when an asteroid struck when they look at rock layers. In rocks from around the globe dating back to the end of Cretaceous period 66 millions years ago, geologists have found a thin layer clay that has been enriched with iridium, an element which is rare on Earth, but very common in space rocks. This was revealed in a landmark 1980 Science study. While other extraordinary events such as wildfires or tsunamis are captivating, Gulick believes that the more important thing was the changes in Earth’s atmosphere. The ghastly shroud caused cooling that lasted over a decade.
He stated that the only way to cause mass extinction is to interfere with something that impacts all of Earth. You can see the direct evidence of it happening.
Original publication on Live Science
