var presentation = ["<word>mass extinction of three-quarters of the plant and animal species on Earth<\/word>","<word>66 million years ago<\/word>","<word>marked the end of the Cretaceous period<\/word>","<word>the end of the entire Mesozoic Era<\/word>","<phrase>The Cretaceous\u2013Paleogene (K\u2013Pg) extinction event, also known as the Cretaceous-Tertiary (K\u2013T) extinction, was a sudden <strong data-readahead=\"mass extinction of three-quarters of the plant and animal species on Earth\" class=\"presentation_word\">mass extinction of three-quarters of the plant and animal species on Earth<\/strong>, approximately <strong data-readahead=\"66 million years ago\" class=\"presentation_word\">66 million years ago<\/strong>. With the exception of some ectothermic species such as the sea turtles and crocodilians, no tetrapods weighing more than 55 pounds survived. It <strong data-readahead=\"marked the end of the Cretaceous period\" class=\"presentation_word\">marked the end of the Cretaceous period<\/strong>, and with it <strong data-readahead=\"the end of the entire Mesozoic Era\" class=\"presentation_word\">the end of the entire Mesozoic Era<\/strong>, opening the Cenozoic Era that continues today.<\/phrase>","<word>the K\u2013Pg boundary<\/word>","<word>metal iridium<\/word>","<phrase>In the geologic record, the K\u2013Pg event is marked by a thin layer of sediment called <strong data-readahead=\"the K\u2013Pg boundary\" class=\"presentation_word\">the K\u2013Pg boundary<\/strong>, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the <strong data-readahead=\"metal iridium\" class=\"presentation_word\">metal iridium<\/strong>, which is rare in the Earth's crust, but abundant in asteroids.<\/phrase>","<word>a massive comet or asteroid<\/word>","<word>66 million years ago<\/word>","<word>halted photosynthesis<\/word>","<word>the K\u2013Pg boundary<\/word>","<phrase>As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K\u2013Pg extinction was caused by the impact of <strong data-readahead=\"a massive comet or asteroid\" class=\"presentation_word\">a massive comet or asteroid<\/strong> 6 to 9 miles wide, <strong data-readahead=\"66 million years ago\" class=\"presentation_word\">66 million years ago<\/strong>, which devastated the global environment, mainly through a lingering impact winter which <strong data-readahead=\"halted photosynthesis\" class=\"presentation_word\">halted photosynthesis<\/strong> in plants and plankton. The impact hypothesis, also known as the Alvarez hypothesis, was bolstered by the discovery of the 112 mi Chicxulub crater in the Gulf of Mexico's Yucat\u00e1n Peninsula in the early 1990s, which provided conclusive evidence that <strong data-readahead=\"the K\u2013Pg boundary\" class=\"presentation_word\">the K\u2013Pg boundary<\/strong> clay represented debris from an asteroid impact. The fact that the extinctions occurred simultaneously provides strong evidence that they were caused by the asteroid.<\/phrase>","<word>gypsum<\/word>","<word>an aerosol<\/word>","<word>acidified the oceans<\/word>","<word>the Deccan Traps<\/word>","<phrase>A 2016 drilling project into the Chicxulub peak ring confirmed that the peak ring comprised granite ejected within minutes from deep in the earth, but contained hardly any <strong data-readahead=\"gypsum\" class=\"presentation_word\">gypsum<\/strong>, the usual sulfate-containing seafloor rock in the region: The <strong data-readahead=\"gypsum\">gypsum<\/strong> would have vaporized and dispersed as <strong data-readahead=\"an aerosol\" class=\"presentation_word\">an aerosol<\/strong> into the atmosphere, causing longer-term effects on the climate and food chain. In October 2019, researchers reported that the event rapidly <strong data-readahead=\"acidified the oceans\" class=\"presentation_word\">acidified the oceans<\/strong>, producing ecological collapse and, in this way as well, produced long-lasting effects on the climate, and accordingly was a key reason for the end-Cretaceous mass extinction. In January 2020, scientists reported new evidence that the extinction event was mostly a result of the meteorite impact and not volcanism. Other causal or contributing factors to the extinction may have been <strong data-readahead=\"the Deccan Traps\" class=\"presentation_word\">the Deccan Traps<\/strong> and other volcanic eruptions, climate change, and sea-level change.<\/phrase>","<word>the non-avian dinosaurs<\/word>","<word>75% or more of all species on Earth vanished<\/word>","<word>adaptive radiation<\/word>","<phrase>A wide range of species perished in the K\u2013Pg extinction, the best-known being <strong data-readahead=\"the non-avian dinosaurs\" class=\"presentation_word\">the non-avian dinosaurs<\/strong>. It also destroyed a myriad of other terrestrial organisms, including some mammals, birds, lizards, insects, plants, and all the pterosaurs.  In the oceans, the K\u2013Pg extinction killed off plesiosaurs and mosasaurs and devastated teleost fish, sharks, mollusks (especially ammonites, which became extinct), and many species of plankton. It is estimated that <strong data-readahead=\"75% or more of all species on Earth vanished\" class=\"presentation_word\">75% or more of all species on Earth vanished<\/strong>.  Yet the extinction also provided evolutionary opportunities: In its wake, many groups underwent remarkable <strong data-readahead=\"adaptive radiation\" class=\"presentation_word\">adaptive radiation<\/strong> - sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches. Mammals in particular diversified in the Paleogene, evolving new forms such as horses, whales, bats, and primates. The surviving groups of dinosaurs were avians, ground and waterfowl who radiated into all modern species of bird. Teleost fish, and perhaps lizards also radiated.<\/phrase>"];
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