The Chicxulub impact and its environmental consequences

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 10 23 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.