Has anyone read the Wikipedia article on the Cretaceous–Paleogene extinction event? If you haven't, check it out. It is the most red-pilling, consciousness expanding thing you will read.
The key takeaway that I never knew about it, and I bet most pepole don't know, was that ALL TERRESTRIAL ANIMALS LARGER THAN 2 KG DIED OUT. All herbivores and carnivores died out (carnivores doesn't include insectivores and omnivores). LITERALLY THE ENTIRE PLANET WAS ON FIRE.
Here are some highlights:
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). Small creatures whose food chains were based on detritus would have a reasonable chance of survival.[81][97] The consequences of reentry of ejecta into Earth's atmosphere would include a brief (hours long) but intense pulse of infrared radiation, killing exposed organisms.[51] Global firestorms likely resulted from the heat pulse and the fall back to Earth of incendiary fragments from the blast. Recent research indicates that the global debris layer deposited by the impact contained enough soot to suggest that the entire terrestrial biosphere had burned.[115]
There is clear evidence that sea levels fell in the final stage of the Cretaceous by more than at any other time in the Mesozoic era. In some Maastrichtian stage rock layers from various parts of the world, the later layers are terrestrial; earlier layers represent shorelines and the earliest layers represent seabeds. These layers do not show the tilting and distortion associated with mountain building, therefore, the likeliest explanation is a "regression", that is, a drop in sea level. There is no direct evidence for the cause of the regression, but the explanation currently accepted as most likely is that the mid-ocean ridges became less active and therefore sank under their own weight.[24][128]
A severe regression would have greatly reduced the continental shelf area, which is the most species-rich part of the sea, and therefore could have been enough to cause a marine mass extinction. However research concludes that this change would have been insufficient to cause the observed level of ammonite extinction. The regression would also have caused climate changes, partly by disrupting winds and ocean currents and partly by reducing the Earth's albedo and therefore increasing global temperatures.[98]
Marine regression also resulted in the loss of epeiric seas, such as the Western Interior Seaway of North America. The loss of these seas greatly altered habitats, removing coastal plains that ten million years before had been host to diverse communities such as are found in rocks of the Dinosaur Park Formation. Another consequence was an expansion of freshwater environments, since continental runoff now had longer distances to travel before reaching oceans. While this change was favorable to freshwater vertebrates, those that prefer marine environments, such as sharks, suffered.[80]
Species that depended on photosynthesis declined or became extinct as atmospheric particles blocked sunlight and reduced the solar energy reaching the Earth's surface. This plant extinction caused a major reshuffling of the dominant plant groups.[23] Omnivores, insectivores and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. No purely herbivorous or carnivorous mammals seem to have survived. Rather, the surviving mammals and birds fed on insects, worms, and snails, which in turn fed on dead plant and animal matter. Scientists hypothesize that these organisms survived the collapse of plant-based food chains because they fed on detritus (non-living organic material).[24][25][26]
Based on marine fossils, it is estimated that 75% or more of all species were wiped out by the K–Pg extinction.[20] In terrestrial ecosystems all animals weighing more than a kilogram disappeared.[21]