‘Everybody has a plan until they get punched in the face.’ —Mike Tyson
The asteroid landed in the ocean and would have caused megatsunamis, for which evidence has been found in several locations in the Caribbean and eastern United States—marine sand in locations that were then inland, and vegetation debris and terrestrial rocks in marine sediments dated to the time of the impact. […]
The asteroid landed in a bed of gypsum (calcium sulfate), which would have produced a vast sulfur dioxide aerosol. This would have further reduced the sunlight reaching the Earth’s surface and then precipitated as acid rain, killing vegetation, plankton, and organisms that build shells from calcium carbonate (coccolithophores and molluscs). […]
The impact may also have produced acid rain, depending on what type of rock the asteroid struck. However, recent research suggests this effect was relatively minor, lasting for approximately 12 years. […]
Such an impact would have inhibited photosynthesis by creating a dust cloud that blocked sunlight for up to a year, and by injecting sulfuric acid aerosols into the stratosphere, which might have reduced sunlight reaching the Earth’s surface by 10–20%. It has been argued that it would take at least ten years for such aerosols to dissipate, which would account for the extinction of plants and phytoplankton, and of organisms dependent on them (including predatory animals as well as herbivores). […]
The event appears to have hit all continents at the same time. […]
The event eliminated a vast number of species. Based on marine fossils, it is estimated that 75% or more of all species were wiped out by the K–Pg extinction. In terrestrial ecosystems all animals weighing more than a kilo disappeared.
The most well-known victims are the non-avian dinosaurs. […]
The fact that the extinctions occur at the same time as the Chicxulub asteroid impact strongly supports the impact hypothesis of extinction. […]
The Chicxulub crater is more than 180 kilometres (110 mi) in diameter and 20 km (12 mi) in depth, making the feature one of the largest confirmed impact structures on Earth; the impacting bolide that formed the crater was at least 10 km (6 mi) in diameter. […] Researchers dated rock and ash samples from the impact to roughly 66 million years ago. […]
Some scientists maintain the extinction was caused or exacerbated by other factors, such as volcanic eruptions, climate change, or sea level change, separately or together.
{ The Cretaceous–Paleogene (K–Pg) extinction event | Chicxulub crater }
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