The Chicxulub impact and its environmental consequences
Joanna V. Morgan, Timothy J. Bralower, Julia Brugger & Kai Wünnemann
Nature Reviews Earth & Environment
Review Article, Published: 12 April 2022
- The Chicxulub impact ended the Mesozoic era and was almost certainly the principal cause of the Cretaceous–Palaeogene (K–Pg) mass extinction.
- Seismic images of the approximately 200-km-wide Chicxulub impact structure reveal that it has the same morphology as the largest impact basins on other solid planetary bodies, such as the Lise Meitner and Klenova craters on Venus.
- Rocks from the impact site and asteroid were ejected within an impact plume and ejecta curtain. Ejection velocity is a function of shock pressure, with the most-shocked rocks leaving the impact site at >11 km s–1 (escape velocity).
- The high-velocity ejecta interacted with the Earth’s atmosphere to form a fast-moving cloud that carried dust, soot, sulfate aerosols and other ejecta around the Earth within 4–5 hours of impact.
- Ejecta within the cloud, along with soot from wildfires, caused the Earth to become dark and cold for about a decade, and induced longer-term (decadal to millennial) temperature changes and chemical changes in the ocean.
- This extended impact winter explains the abruptness and severity of the mass extinction, as well as its selective impact on different organisms.”
“The extinction of the dinosaurs and around three-quarters of all living species was almost certainly caused by a large asteroid impact 66 million years ago. Seismic data acquired across the impact site in Mexico have provided spectacular images of the approximately 200-kilometre-wide Chicxulub impact structure. In this Review, we show how studying the impact site at Chicxulub has advanced our understanding of formation of large craters and the environmental and palaeontological consequences of this impact. The Chicxulub crater’s asymmetric shape and size suggest an oblique impact and an impact energy of about 1023 joules, information that is important for quantifying the climatic effects of the impact. Several thousand gigatonnes of asteroidal and target material were ejected at velocities exceeding 5 kilometres per second, forming a fast-moving cloud that transported dust, soot and sulfate aerosols around the Earth within hours. These impact ejecta and soot from global wildfires blocked sunlight and caused global cooling, thus explaining the severity and abruptness of the mass extinction. However, it remains uncertain whether this impact winter lasted for many months or for more than a decade. Further combined palaeontological and proxy studies of expanded Cretaceous–Palaeogene transitions should further constrain the climatic response and the precise cause and selectivity of the extinction.”