End of the World of Dinosaurs - Essay Example

End of the World of Dinosaurs Other (s) End of the World of Dinosaurs Introduction Dinosaurs were a diverse group of animals that first made their appearance during the Triassic period and remained one of the dominant terrestrial vertebrates until the end of the Cretaceous period( about 65million years ago), when they eventually became extinct. For nearly 135 million years, dinosaurs dominated Earth. They came in different sizes with some dinosaurs considered to be the largest land animals of all time while others were smaller than Turkey. From the earlier days of geology, the issue about the end of the world of dinosaurs has remained to be a challenge among a number of scientists (Urquhart 268). The unexplained demise of this group of animals that was associated with immense diversity and vigor by the end of the Cretaceous period remained a challenge even to the law of the fittest as well as the theory of evolution. Similarly, many of the dinosaur paleontologists have kept asking questions about the dinosaurs going extinct. However, although scientists have not agreed entirely on the exact cause of the mass of dinosaurs, there are a number of theories that have been put forward to explain the possible causes of the end-Cretaceous extinction that may have also resulted in the lost of more than 50% of the Earth’s species. This paper critically analyzes the end of the world of dinosaurs with particular focus to the major theories explaining their eventual demise on the face of the Earth. Fig 1: Skeleton of a Dinosaur How the World of Dinosaurs came to and End Scientists concur that all dinosaurs had died out at the end of the Cretaceous period. In an attempt to explain this mystery, a number of models and ideas have been proposed with the intention of accounting for the fall from the grace of dinosaurs. Two of the most common proposals are gradualist theory and the impact theory (Debus and Mark 176). The gradualist theory points to reduction in the diversity and number of varied groups of marine and land animals. It asserts that the disappearance of these groups was based on climatic change; the climate towards the end of Cretaceous period was characterized by cooling plus a fall in the sea level thus resulting in reduction in the habitats of dinosaurian plus the shallow water marine animals. On the other hand, impact hypothesis happens to get much of press coverage based on its spectacular nature. There is sufficient evidence supporting the scene of an asteroid impact at the fall of Cretaceous. According to many researchers, the asteroid may have been about 10 kilometers in diameter struck the earth at a place presently known as the Yucatan peninsula, Mexico (Tanner and Chapman 123). All through the world, people have come across some band of deposited clay that is rich in iridium; the mineral is scarce on earth though more common within the meteorites. Suggestions have been made earlier on that the impact might have brought about a nuclear winter scene that might have resulted into death of the dinosaurs alongside pterosaurs, mammals, marine animals and many families of birds. In addition to the two theories described above, there exists yet another theory referred to as volcanic theory. The theory attributes the end of the dinosaurs to the volcanic eruptions that took place in certain parts of the world. This resulted into deposition of huge flood basalts and Deccan traps during this period and the produced dust and gases that erupted at the selfsame time might have resulted into environmental changes covering a larger area. The occurring environmental changes are believed to have resulted into weather conditions or ecological environments that were no longer habitable by the dinosaurs. According to Tanner and Chapman (125), whereas the presented hypotheses are plausible and are capable of offering explanations on the number of animals that went instinct, it is unfortunate that none of them is able to explain why some animals managed to survive while others died out. Probably, the most popular theory explaining the demise of dinosaurs currently is the Asteroid theory. For example, many scientists believe that a large collision between the earth and a super large comet or asteroid may have thrown so much dust into the skies that blocked sunlight for several years leading to the mass extinction of plants and animals as was witnessed during the late Cretaceous period extinction. The quick and rapid extinction of the dinosaurs is a confirmation the impact mat have resulted in a cataclysmic end. As earlier been noted, the asteroid may have been about 10 kilometers in diameter struck the earth at a place presently known as the Yucatan peninsula, Mexico. The dense clouds of dust and smoke may have continued to block the rays of the sun, thereby chilling and darkening Earth to deadly levels for plants and eventually for many animals. On the other hand, when the dust eventually settled, the greenhouse effect created by collision impact could have caused the temperatures to skyrocket several times above pre-impact levels. In this regard, some of the possible catastrophic effects of the impact may have included spread of global fires, a long period of extremely cold weather due to the blockade of sunrays by smoke and dust, and finally, a possibility of very hot climate due to high levels of carbon dioxide that may have been released into the atmosphere due to the impact. Generally, these dramatic climatic changes may have resulted from the huge asteroid collision may have been what led to the extinction of the dinosaurs as they were not able to adopt and survive. According to this hypothesis, in just a couple of years, the extreme climatic changes may have resulted in the extinction of not only the dinosaurs but also up to 50% of all the animals and plant species living at the time. For example, these changes are likely to have impacted on the planets ecosystem at the time as most plants could no longer effectively photosynthesize due to blockaded sun rays making many of the plants to die off. In turn, the herbivorous dinosaurs may have followed before the eventual eradication of carnivores too. There is a significant number of evidence that seem to suggest that the impact actually took place at the end of the end of the Cretaceous period as postulated by the Asteroid impact theory. For example, scientific evidence of the devastation of the terrestrial vegetation after the impact has been found in the form of thin rock layers deposited. However, many paleontologists believe that dinosaurs may have been already in a rapid decline even before the asteroid impact took place, and therefore the environmental effects of the impact merely served to hasten the extinction of the dinosaurs. According to many scientists, the existence of a 150 kilometer wide crater just off the Yucatan peninsula in Mexico also suggests that asteroid impact theory may be true. For example, it has been concluded that impact hat created the crater actually took place 65 million years ago and the dates seemingly correspond well to the period of dinosaur extinction. On the other hand, presence of extremely rare metal known as iridium, which is common in most asteroids but very rare on the earth surface, is another possible indication that the great asteroid impact may have actually took place. For instance, scientists recently discovered greater levels of iridium with up to 30 times greater than average levels in the sedimentary rock layer that was laid down at the time of the mass extinction of dinosaurs. The other critical evidences of this theory include the presence of pieces of molten rock (impact ejecta) which is an indication that the explosion was so powerful enough to instantly melt some of the bedrock before propelling them several miles away from their point of origin. The impat ejecta rocks are commonly found along the geological rock layers that are associated with the period of dinosaur extinction (Urquhart 281). Additionally, the fractured crystals (commonly known as the “shocked quartz” that are found around the Yucatan peninsula in Mexico have a distinctive fracturing pattern that is consistent with high energy explosions such as by a massive comet or asteroid impact. Lastly, based on the fossil records, it has been determined that dinosaurs were actually doing well before the end of the cretaceous period when the impact is likely to have occurred. Generally, the sudden demise of dinosaurs as seen in the fossil records is a likely indication that their ultimate demise on the face of the earth had a catastrophic cause. A gradual decline of dinosaurs in the fossil records would have indicated a gradual cause of their extinction. Conclusion In conclusion, regardless of the conflicting details found in the different theories, it is a common thought that the dinosaurs reached the end of their evolutionary life at the end of the Cretaceous period. In all the scenarios presented in this paper, their inevitable extinction is largely attributed to inability to cope up with the drastically changing ecosystem due to climate change and competition from other mammals of their time. Works Cited Debus, Allen A and Mark F. Berry. Dinosaurs in Fantastic Fiction: A Thematic Survey. Jefferson, N.C.: McFarland, 2006. Print. Tanner, L. Lucas and Chapman, Michael G. “Assessing the record and causes of Late Triassic extinctions.”  Earth-Science Reviews 65.1(2004):103–139.Web. 02 May, 2014. Urquhart, E. Young. “The Cretaceous-Tertiary biotic transition.” Journal of the Geological Society 154.2(2007): 265–292.Print. Read More