How a Meteor Killed the Dinosaurs and How we Know it Happened

looking through the earth's rock layers you can see sudden and drastic changes in their geologic composition often accompanied by the plants and animals that would have occupied these periods suddenly changing as well since the days of when early naturalists first realized there was a long deep time that had existed before humans they knew that these different layers represented different time periods and so they categorized and named them however the reason why the layers were in fairly well defined segments was not so well understood in the 1800s different people had different explanations for these rock layers richard owen the legendary paleontologist who coined the phrase dinosaur believed that the time periods were distinctly separate eras or phases where the animals and plants that occupy them had been improved however with the combined discovery of evolution by natural selection and that animals could actually go extinct came new explanations for this phenomena the dividing lines between the geologic periods weren't that distinct and what actually separated them were big changes in the ecosystem often like a cataclysmic event causing a huge number of species to go extinct after a mass extinction there would be vacant niches left open for the survivors to colonize and so in a relatively short amount of time the flora and fauna would drastically change as it evolved to fill the empty niches with a range of new plants and animals occupying the planet the geologic footprint they left over may also change there have been many mass extinctions throughout history that often fit comfortably between the dividing lines of two geologic periods and the one that killed off the non-bird dinosaurs also known as the kpg extinction wasn't even the worst but it was the last time that saw a very quick and dramatic shift in the dominant animals in the earth's ecosystem it is common knowledge now that the cause of this dinosaur disappearance was a giant meteor the size of a mountain but how was this actually found out and how did it change the earth in such a long and far-reaching way in the cretaceous rock layer fossils of non-avian dinosaurs are abundant but then after it in the blink of a geological eye they had all but vanished and in the following period the paleogene mammals were much larger and more diverse this change in the earth's ecosystems had been known about to people for many years and many theories were posited to explain it and amazingly despite it being widely known about today a giant meteor being the explanation for the death of the dinosaurs only saw widespread acknowledgement among the scientific community in the late 80s a meteor had been suspected before but the first material evidence for the catastrophe was only discovered in 1980 there is a thin layer of clay sitting between the cretaceous and paleogene boundary that can be found in many different parts of the world that is filled with a metal known as iridium iridium is very rare in the earth's crust so it was puzzling why so much of it could be found between these two layers specifically father and son scientists louis and walter alvarez proposed an extraterrestrial origin for the iridium suggesting that it must have come from an ancient meteor that crashed into the earth azeridium may be rare on earth but it is common in asteroids in the same layer of clay where the iridium was found there were tectites small bits of natural glass that can form when the earth has been heated at incredibly high temperatures and the alvarez team suggested that these were the debris kicked up by the asteroid impact due to the amount of debris that could be found and the thickness of the cretaceous paleogene boundary in some parts of the united states the alvarez team thought that the crater left by this giant meteor may be somewhere fairly close by in the yucatan peninsula in southern mexico there is a beautiful natural formation of sinkholes known as cenotes cenotes form when there is an erosion of water underneath the ground until the roof eventually caves in forming a hole filled with water cenotes are abundant across the entire area but when mapped out there are a concentration of them forming a semicircle that meets the ocean at both ends the circular shape these cave systems are arranged in has been known about for a while and it was always a bit of a mystery however in the 1990s after the proposal of the asteroid impact a team of scientists thought this may be the remnants of the impact crater and the cenotes were leftovers from the edge of the crater where the rocks were mangled and weakened by an otherworldly force like a meteor strike the crater was dated to 66 million years old and was about 90 miles in diameter around the same size that the alvarez team calculated that it should be 66 million years ago a piece of rock around the same size as mount everest hurtles towards the earth for 40 000 miles per hour its entry into the atmosphere would have been met with a brief but bright light before the impact penetrated into the earth's crust to a depth deeper than the ocean floor instantly vaporizing every plant and animal up to 500 miles away in under 10 seconds like it is today much of the impact zone was over water and the huge displacement of the sea would have caused mega tsunamis that would have been well over 100 meters high and reached far far-off lands evidence of these can be found 2 000 miles away in north dakota where a massive amount of marine life and sediment was hurled from the ancient seaway that used to exist here onto the land the beginning stages of this catechism may have been spectacularly violent but it was a string of global catastrophes that the initial impact ignited that ultimately spelled the end of the non-avian dinosaurs and many other animal groups killing off three-quarters of all species on the planet and the reason that there was a selection of specific animals that went extinct most devastating was a death of most plant life that occurred after the impact in the layers of rocks just after the impact there is an incredibly high amount of just a few species of plants specifically more than 70 percent of all fossilized fern spores were from just two species this happens after there is a huge die off because the survivors have a brief window of time where there is little to no competition and so will quickly spread out and grow where the other plants have fallen there would have been widespread forest fires that would have engulfed much of the world's flora but also the impact would have kicked up a dust cloud coating the earth in a blanket of debris and soot they may have blocked up to 50 percent of sunlight in some regions this would have caused the earth's temperatures to plummet for years after the impact but also plants would be unable to photosynthesize although there is disagreement to what extent either forest fires or lack of sunlight were to blame for the death of plant life the one thing that was for certain is that the planet was left almost barren from greenery for a long time after the impact and this would have caused the extinction of the vast majority of dinosaurs with a massive reduction in plant life the giant herbivorous dinosaurs like ceratopsians and sauropods wouldn't be able to fill their colossal dietary requirements and following their disappearance it would have been incredibly hard for the large carnivorous dinosaurs to find enough food to survive either the catastrophic damage that had been done meant the planet just couldn't support large animals anymore most of the devastating effect the impact of the asteroid had on the planet tends to be focused on the dinosaurs and other land animals but of course many prehistoric sea creatures like giant marine reptiles also went extinct at the same time and the effect the impact had on the ocean was as bad or maybe even worse around the same time that the asteroid hit the planet there is evidence that the ocean saw a massive increase in acidity and it is thought that this may have been caused by the impact the gas cloud that was ejected into the atmosphere by the asteroid contained sulfur dioxide which polluted their clouds and caused acid rain that would have lowered the ph in the oceans around the world an acidic sea can spell disaster for ocean dwellers because it reduces the availability of calcium carbonate which invertebrates used to create their shells and exoskeletons so the massive increase in the acidity in the oceans made it much harder for mollusks and other animals to create their shells causing many of them to go extinct ammonites went from being very successful to completely extinct in a blink of an eye and as much as 90 percent of shelled animals in general also went extinct as the smaller shelled animals were missing from the ecosystem this would have had a larger impact on the food chain as a whole including the big marine carnivals of the time the large marine reptiles like mosasaurs as the dust clouds cleared as much as a decade later and the climate became more stable the earth would have been a very different place as for some time after the event the earth was mostly populated by little animals that survived the extinction because they needed less food and usually had more varied diets of course small dinosaurs that may also have been opportunists went extinct as well but there are advantages that the survivors like certain reptiles mammals and birds have over dinosaurs in the environment that would have followed the event which might be why they survived lizards and crocodiles have famously slow metabolisms and can survive months or even years without food and so as long as they were outside the blast radius they had a good chance of surviving until the ecosystems had recovered slightly before needing food again because birds are able to fly they could travel long distances to seek out resources in times of scarcity pterosaurs were able to fly as well but by the end of the cretaceous they were a much less common sight in the skies than birds although birds survived the extinction the majority of them went extinct and so by virtue of their just being less pterosaurs would have made their survival less likely finally mammals most likely survived because they had fur and are capable of creating high body temperatures which would have meant they would have fared much better than dinosaurs in the freezing temperatures that would have occurred after the sunlight was blocked out so in the blink of a geological eye the earth was irrevocably changed forever the many features that dinosaurs had that made them so successful for such a long time were completely turned against them being dethroned by the small flexible and adaptable animals this big change being immortalized in the rock layers is a small blip with two very different earths before and after thank you for watching a big thank you goes to all my 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Channel: Moth Light Media

Views: 97,705

Rating: 4.9583044 out of 5

Keywords: Extinction of the dinosaurs, dinosaurs, K-Pg Extinction, K-T Extinction, Mass extinctions, paleontology, history of paleontology, why mammals survived, mammal evoluition, ancient history, prehistory, meteor strikes, yucatan cenotes, asteroid impact, asteroid, extinction events

Id: T1F2mXbl4RA

Length: 10min 50sec (650 seconds)

Published: Thu Oct 01 2020