Dinosaurs, disappearance

This iridium clue is a key, therefore, to understanding how dinosaurs disappeared from Earth. And could explain why they, and so many other species of plants and animals, died out so suddenly. 

Scientists continue to debate the cause of the dinosaurs disappearance. 

Major catastrophes that lead to mass extinction of species occurred five times in Earth s history during the last 540 million years the last one was 65 million years back (end of the Mesozoic) when the dinosaurs disappeared. The high rate at which species are disappearing has led scientists to suggest that the sixth mass extinction is already under way Barnosky estimates that in 330years, 75% of mammalian species will be extinct (Barnosky et al., 2011). 

Mesozoic Triassic 245 Myr Continents begin to drift apart. Early dinosaurs first mammals gymnosperms become dominant diversification of marine invertebrates. Moss extinction at end of period (ca. 75% of all species disappear)... 

After a warm period, in the Pangea/Panthalassa arrangement of Earth about 210 My ago, the end-Triassic mass mortality caused the disappearance of mammal-like reptiles leaving place to the dinosaurs, the first angiosperms, and the first mammals. 

Climate changes from the time ofthe disappearance of dinosaurs to our days have also been based up on deep-sea stable isotope data oxygen isotope data provide an insight into the temperature variations, while carbon isotope data are informative on the kind of global carbon cycle perturbation (Zachos 2001). These data suggest that the present conditions of temperature are similar to the late Middle Age. However, the trend toward higher temperatures is now more difficult to contrast because of the drastic deforestation and emission of gases. 

Iridium is a lesser-known transition metal, but it has become a famous clue in the mystery of how and why the dinosaurs became extinct 65 million years ago. There is an unusually large amount of iridium in rock layers all over the world that date to the time of the dinosaur die-off. In 1980, a team of scientists suggested that the iridium came from a huge meteorite that struck the Earth 65 million years ago, creating firestorms and throwing up a huge dust cloud all around the planet. Many other plants and animals disappeared at the same time as the dinosaurs, and so far the massive meteorite strike is one of the most convincing explanations for all these extinctions. 

Could you invert your computations applied to the tertiary, 75 million years ago, to the disappearance of dinosaurs In this case we do know that something happened but we do not know the megatons. 

If photosynthesis were to cease, all higher forms of life would be extinct in about 25 years. A milder version of such a catastrophe ended the Cretaceous period 65.1 million years ago when a large asteroid struck the Yucatan Peninsula of Mexico. Enough dust was sent into the atmosphere that photosynthetic capacity was greatly diminished, which apparently led to the disappearance of the dinosaurs and allowed the mammals to rise to prominence. 

Iridium s Link to Dinosaur Extinction Iridium occurrences may hold the key to solving the mystery of why the dinosaurs went extinct. The question of what happened to the dinosaurs has long been one of the most interesting and puzzling issues in science. What happened to make these huge reptiles disappear in such a short period of geologic time ... 

Dinosaurs dominated life on Earth for millions of years and then disappeared very suddenly. 

Similar extinctions took place on a much larger scale at the end of the Cretaceous about 66.5 million years ago when dinosaurs, ammonites, and many other plant and animal groups declined and often disappeared. This is evidenced by the accumulation of deposits containing anomalous iridium accumulations of up to 160 times the background level. A similar iridium anomaly was recorded in the Lower to Middle Jurassic of the Venetian area of northern Italy. These earlier extinction episodes cannot be related to human hunters, but rather to astronomical and other forcing factors. Ice ages must have been important also and they too were influenced by these same factors. 

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