Theories of the Extinction of the Dinosaurs
Controversy surrounds the extinction of the dinosaurs. According to one theory, dinosaurs were slowly driven to extinction by environmental changes linked to the creeping withdrawal of shallow seas from the continents at the end of the dinosaur era. Proponents of this theory propose that dinosaurs dwindled in number and variety over several million years.
An opposing theory proposes that the impact of asteroid or comet caused catastrophic destruction of the environment, leading to the extinction of the dinosaurs. Evidence to support this theory includes the discovery of a buried impact crater (thought to be the result of a large comet striking the earth) that is 200 km (124 mi.) in diameter in the Yucatan Peninsula of Mexico. The spray of debris was blown from the edge of the crater. The debris has been found over large regions of North America. Comet enriched material from the impact's fiery explosion was spread all over the world. With radiometric dating, scientists have used the decay rates of certain atoms to date the crater, spray of debris, and fireball layer. Using similar techniques to date the dramatic changes in the record of microscopic fossils, they have found that the impact and the dinosaur extinction occurred nearly simultaneously.
Although great amounts of ash suggest that most of North and South America was devastated by fire from the impact, the longer-term environmental effects of the impact were ultimately more deadly to life than the fire. Dust blocked sunlight from the earth's surface for many months. Burned sulfur from the impact site, water vapor and chlorine from the oceans, and nitrogen from the air combined to produce a worldwide fallout of intensely acidic rain. Scientists postulate that darkness and acid rain caused plant growth to die. As a result, both the herbivorous dinosaurs, which were dependent on plants for food, as well as the carnivorous dinosaurs, which fed on the herbivores, died out. On the other hand, animals such as frogs, lizards, and small insect-eating turtles and mammals, which were dependent on organisms that fed on decaying plant material, were more likely to live.
The possibility if a meteor strike as the cause of extinctions is discarded, something that most specialists agree on. There is no evidence of any meteor crater big enough or recent enough to be accountable for it; there are no “elements that are common extraterrestrially but less so on Earth, such as iridium, and no sign of a tsunami or other phenomena following the impact.” The extinctions where also very selective and occurred over a very long period of time. If a “one shot” catastrophe had been the cause it would have affected all species at the same time and in similar
In order to better understand these "implications," it is necessary to define and explain the major theories regarding North American megafaunal extinction. The two most widely supported theories are those of environmental change and overkill. Two theories finding less support within the field are those of hyperdisease and "keystone herbivores."
The Permian-Triassic Extinction is a mass extinction that occurred between the Permian and Triassic geologic time periods approximately 250 million years ago; it is the deadliest of all extinctions that have occurred on Earth. In addition, during the Permian-Triassic extinction the continents of today existed as one supercontinent known as Pangaea. This was the first time in history where continental or land mass exceeded that of the ocean. This was also before dinosaurs of the Triassic period roamed Earth, during this time animals such as the therapsids, and Synapsids such as the Pelycosaurs, insects and amphibians also occupied Earth. Fauna that existed during the Permian period includes Gymnosperms, or seed producing plants such as the Conifers. Other animals that existed during this time include marine life such as brachiopods (clams), bryozoans (coral-like skeletons), bony fish and sharks, as well as crinoids (sea urchin like creatures). According to National Geographic, about 90 percent of all the animals and fauna of this period perished, the marine life was hit the hardest wi...
Knapp, Alex. "Asteroid Impact Was The Coup De Grace For Dinosaurs." Forbes.Com (2013): 2. Business Source Premier. Web. 13 Jan. 2014.
Sex, drugs, and disasters are both popular topics that grab public attention and scientific theories of the extinction of dinosaurs. While sex and drug hypotheses represent silly speculations, the disaster claim is good science: it provides testable evidence, has an impact on other scientific fields, and generates continuous research.
Because dinosaurs are animals that lived millions of years ago, we are entirely dependent on the fossils that they have left behind for any understanding that we hope to gain. As any paleontologist will tell you, fossil hunting is difficult. There are no certainties, no guarantees. A certain amount of luck is as valuable as any scientific knowledge.
The Permian Triassic extinction was an event of cataclysmic disaster and almost the extinction of all species on planet earth. The Permian Triassic extinction is said to have occurred millions of years ago, geologist have estimated that its occurrences happened about 248 million to 286 million years ago. This rare occurrence of events proceeded the Triassic geologic periods and the Paleozoic and Mesozoic eras. This mass disaster was the largest dissipation of living life on planet earth; it is believed to be even superior to other crises such as the Ordovician and Devonian events and the conclusion of the cretaceous era that came upon the dinosaurs.
With the introduction of radiocarbon dating the accuracy of which fossil and other samples can be determined are greatly increased. Radiocarbon dating promises to predict fossils within 50,000 years to be recorded with precision. With this advancement, the ability to thoroughly analyze extinction periods of certain species would greatly increase. This leads to a stronger understanding of precisely when these events took place and what their causes may be. Martin goes on to provide an example of the woolly mammoths that survived for thousands of years longer than previously believed on remote islands. With radiocarbon dating, it is now understood that populations of mammoths in certain locations were subject to a different rate of extinction. How could this be the case? Martin states, in reference to the mammoths that survived on remote islands that they, "were temporary refugia, bypassed by the first Americans."(Martin,50) Martin implies that the dramatic differences in the extinction of two populations of the same species is due to the involvement of human interactions during the early colonization of the Americas. This correlation is made when examining previous outbursts of extinctions across the world. One of these outbursts occurred around 13,000 years ago, the same time the extinction of mammoths became prevalent within the same regions of North America.(Martin,50) This shows that the difference in extinction periods between locations in North America and on various islands is differentiated by arrival of human populations. The extinction of the mammoths in North America 13,000 years ago, compared to mammoth on the islands of Wrangel 4,000 years ago conclude rapid human expansion of the Americas was the cause of earlier extinction
We use dinosaurs to represent the changes in nature that have occurred throughout time. Studies found that although the “oldest rock did not show evidence of life, the progression of plant and animal life that changed in recognizable intervals, from ancient life, age of reptiles to the age of mammals” (Dino Nature Metaphor, slide 6), measured the age of the earth. When we think of dinosaurs in relation to nature, we think of that very powerful force that controls the cycle of life. Nature was able to yield such magnificent ferocious creatures that walked the earth and then take them back when they served nature’s purpose. Dinosaurs fit perfectly in nature’s constant
In the essay “Sex, Drugs, Disasters, and the Extinction of Dinosaurs” scientists come up with several theories of how the dinosaurs could have possibly become extinct. They tell three of the leading theories as to how they think the dinosaur era extinction happens. The whole thing is a big conspiracy. These theories are government cover-ups to keep us from knowing things. The government knows things that they don’t want us to know, but I already know what happened. The extinction of the dinosaurs are the effect of alien activity on and around Earth.
The most significant event of the Cretaceous era came at its end. Nearly 65 million years ago, the second most severe mass extinction in earth’s history occurred. This resulted in the loss of around 80% of species living at the time. Though nowhere near as severe as the end-Permian mass extinction, the end-Cretaceous extinction is the most well known mass extinction event. This is due to the violent event that caused it the extinction, as well as the chapter of earth’s history that it closed: the Dinosaurs. The Cretaceous Event ( often shortened to K-T event) Of the animals that were killed off were the flying reptiles (pterosaurs) and the last few mosasaurs and plesiosaurs, both early marine reptiles. Many mollusks and species of microscopic plankton were killed. Terrestrial plants suffered mass extinction as well. Almost 60% of terrestrial plants were lost. This led to high extinction rates among insect populations, especially insects that were highly specialized to feed on just a few types of plants had it the worst. It took approximately 9 million years for the global insect populations to recover from the Cretaceous extinction. Immediately after the extinction, the earth saw an explosion of short term species who respond well to fire, or other external disturbance. Evidence of the catastrophe comes from a thin rock layer deposited worldwide just after the impact. It is dominated by fossil plants whose descendants recover quickly after fires of other disturbances, such as Fire Weed in Alaska. The causes of the Cretaceous extinction are still being debated by paleontologists. Scientists agree that the main cause of the extinction was a...
seems like it happened so sudden, as geologic time goes, that almost all the dinosaurs
Almost 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species went extinct (Beaz). Although the cause of this mass extinction is debatable, many speculate that global warming was the killer. Because Pangea was breaking up into Laurasia and Gondwanaland, there was widespread volcanic activity caused by the rifting, increasing atmospheric carbon dioxide. The massive release of this greenhouse gas increased global air temperatures and resulted in acidified oceans along with rising sea levels. If this is the case, the life in the ocean would have died at a significant rate. Many families of brachiopods, gastropods, bivalves, and marine reptiles became extinct (Rafferty). An important trace fossil known as the phylloceratid ammonoid was able to survive, and they gave rise to the explosive radiation of cephalopods later in the Jurassic Period, as well as evolved into many different forms during the later Cretaceous (End Triassic Extinction). This extinction event ranks fourth in severity of the five major extinction events over geologic history
Several mass extinctions have occurred during the Earth’s history. The Cretaceous – Tertiary Boundary (K-T) Extinction caused the loss of at least three-quarters of all species known at that time including the dinosaurs. The cause of this mass extinction is a controversial subject among scientists but the fossil evidence of it’s occurrence is abundant.
The most popular theory of dinosaur extinction, the asteroid theory, says that dinosaurs died out because of a single, giant asteroid. They say that the asteroid that struck the earth near the Gulf of Mexico went 43,000 mph and spanned six miles wide (Erdman). When it hit the Earth the asteroid it left an enormous crater that measured 24 miles deep and 125 miles wide (Erdman). Just the impact of the asteroid destroyed the forests and landscape of the majority of North America due to its massive shock wave (Erdman). Many species went extinct when the asteroid hit, these species include dinosaurs, ammonites (certain ocean dwelling creatures), pterosaurs, and some plant groups dinosaurs, ammonites (mollusks related to the octopus and the chambered nautilus), pterosaurs, and certain plant groups. Although devastating, the asteroid did not wipe out all of the animals on Earth, it didn’t exterminate fish, frogs, turtles, birds, mammals and croco...