Extinction of Dinosaurs
Two-hundred and thirty million years ago the first dinosaur-like creature roamed the earth. Within five million years it could be considered a dinosaur. They were soon at the top of the food chain. They populated every continent. Then 65 million years ago they vanished. The most powerful creatures ever to live on earth had become extinct.
Dinosaurs were not the only victims of this "mass extinction." There were many other species that were killed off. During what is known as the K-T extinction (K stands for Cretaceous, T stands for Tertiary), many species and families became extinct. These include all marine reptiles such as
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Any one of these events, theorized by paleontologists, could have brought an end to the dinosaurs and all the other species that died with them. Since there are many theories about this I will not write about them all.
I have chosen the theory about death by Cosmic Collision (an asteroid).
In 1980 Luis Alvarez and John Sepkowski Jr., famous geologists, blamed the extinction of the dinosaurs on a large celestial body which hit the Earth 65 million years ago. According to them, an asteroid five miles across blasted through the Earth's crust, and threw up molten rock, ash, and dust. Adding to the support to this theory is the discovery of a layer of iridium in New Zealand,
Denmark, and Italy. This layer became known as the iridium anomaly. Remarkably, this layer of iridium was found in sedimen tary rock that is abundant on other celestial bodies. This was too remarkable to be a coincidence, so the research team decided that the layer of iridium must have been caused by space debris which resulted from the collision of Earth and another celestial body. At first,
Alvarez's theory was not widely accepted, but as more iridium was found from that period of time around the world, it became the leading theory. Other evidence includes the discovery of stishovite, a mineral created by high heat and pressure. These two
So what killed the dinosaurs? Without having any background education in science it is hard for the general public to comprehend such matters and they rely on the knowledge of the scientists in this field. Although there has been much research on the subject nobody has come up with a conclusive answer. And we are left to read the countless articles, all having their own opinions as to the mass extinction. One such theory is that a shift in the solar system could have caused the mass destruction. According to an article published in Nature magazine,
Large amounts of iridium – a chemical element that is not a part of the Earth’s crust composition – were originally found in rocks of Europe and United States, and have been found everywhere ever since. Iridium, common in meteorites, is a testable evidence of the disaster hypothesis. Gould continues that the Cretaceous debacle, which is one of five episodes of mass dying, occurred at the same time as the large comet might have smashed into the Earth. The author believes this is not merely a coincidence, rather, it is a proof of the cause-effect relationship. The demise of a wide range of habitats along with the extinction of dinosaurs gives an inestimable advantage to the disaster theory over other claims, the author adds. The comet struck the Earth, and habitats, from terrestrial to marine, died with geological suddenness. Finally, this hypothesis has had an impact on the study of an atomic war and its consequences. A nuclear war, Gould says, may cause a huge drop in temperatures and result in the extinction of humanity. Testable evidence, study, development, contribution – all this makes good science.
Stephen Gould’s essay “Sex, Drugs, Disasters, and the Extinction of the Dinosaurs” completely agrees with Joseph Williams and Gregory Colomb’s essay “Argument, Critical Thinking, and Rationality.” Gould’s essay deals with three theories for the extinction of the dinosaurs, two of which he argues are entirely invalid because they are not in accordance with the basic rules of argument laid out by Williams and Colomb in their essay. Gould also states that the third theory of dinosaur extinction, natural disaster, follows all the rules that Williams and Colomb espouse, and thus is a sound argument. Gould, Williams, and Colomb all state that the world has a problem with irrational arguments being shoved down people’s throats, and call for a
Gerta Keller, professor of geosciences at Princeton University, has recently conducted research on the Chicxulub asteroid in which she analyzed new core samples taken from the asteroid site (Botzer 2004). These samples indicate that the impact that occurred at Chicxulub actually predated the mass extinction of the dinosaurs, which occurred at the Cretaceous-Tertiary boundary about sixty-five million years ago. Keller claims that the Chicxulub impact occurred approximately 300,000 years before the extinction (Keller 2004). Although previous researchers estimated that the Chicxulub asteroid was the cause of the extinctions, there had always been doubts about the exact age and size of the crater, and about the origin of the “mega tsunami deposits” that were located within the crater (Keller 2004). The focus of Keller’s recent research was on finding some answers to these questions. To do so she analyzed Cretaceous limestone, dolomite, and anhydrite deposits as the site of the Chicxulub crater (Keller 2004).
Despite a family history of geophysicists and rock enthusiasts, I’ve never found the subject of rocks particularly fascinating. However, an exploration of Earth Science has lead me to the discovery that rocks are actually hidden gems (often literally), and that there’s more to the topic than one would think.
He narrowed his hunt down to a location in Denmark, where he had sent a colleague to perform an iridium analysis test at ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). When the results came back, Alvarez knew that whatever happened had not been a small-scale disaster. Once again, Alvarez was back to asking questions. What caused the increased iridium levels at the KT boundary? Except this time, he realized that his observations supported the ten year old hypothesis that had been proposed by paleontologist Dale Russell and physicist Wallace Tucker ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). They brought up the possibility of a supernova being the cause of dinosaur extinction. Supernovas are known to release high amounts of iridium, so such a hypothesis fit perfectly with Alvarez’s team’s discovery. However, the hope of having found a conclusion was short-lived. Luis Alvarez had mentioned that if said supernova had occurred that it would have released amounts of plutonium which would have been found alongside the iridium; no plutonium was found at either site. After more digging, the team came up with a new hypothesis ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). Perhaps an asteroid had struck Earth towards the end of the Cretaceous period, blowing enough dust into the atmosphere to
The scale and pace of change is dramatic; for example, the extinction of species is occurring at around 100-fold pre-human rates4. The population sizes of vertebrate species have, on average, declined by half over the last 45 years5. More than 2.3 million km2 of primary forest has been felled since 20006. About
Dinosaurs ruled the earth for over 65 million years and thankfully for the human race, they became extinct. Ultimately, only a major catastrophe could completely wipe out an entire species, let alone an entity of dinosaurs and the debacle on the causes of dinosaur extinction have flooded the minds of paleontologists for centuries. Geologist and zoologist Stephen Jay Gould published “Sex, Drugs, Disasters, and the Extinction of Dinosaurs,” to compare scientific and speculative causes of dinosaur decimation. Personally, I found this passage very informational and enjoyed reading it. Gould provides three theories that capture the reader’s curiosity, allowing room for pondering in one’s mind.
8. The periods in which there were mass extinctions are Permian – volcanic eruptions which spewed lava and put CO2 into the air which warmed the climate an estimated 6 degrees Celsius. The resulting of oxygen deficiency. And Cretaceous – asteroid or comet
The main dinosaurs that died off were Sauropod dinosaurs, long necked, four legged dinosaurs, and stegosauridae, class holding Stegosaurus. Other species that died include ammonites, similar to the living animals called nautilus, many marine reptiles, and bivalves, relatable to modern mollusca. Not much is known about this extinction. It is mainly linked to climate change. So far, no connection to volcanic activity or an asteroid has been made. This extinction gave way to the Cretaceous Period.
In a summary, Kolbert explains the extinctions of a variety of different major animal species that became extinct. She also explains that if trends in the environment continue that the biggest extinction in history will occur soon. If global warming, deforestation, and glaciers continue to melt she says that more and more species will continue to become extinct. She explains how humans need to be more conservative and careful with what they’re doing to prevent extinction.
According to the research made by Alvarez (1980), it was due to an asteroid impact that single-handedly destroyed dinosaurs to extinction. Advocacy of this mechanism has been aided by the availability and tangibility of supporting evidence in the form of impact craters- the Chicxulub crater in the Yucatan Peninsula's date and timing of impact (dating produced an almost exact date of 65 million years ago), location, enormous size-170 km (Hildebrand et al.1991) and its high iridium content ( a metal not commonly found at the Earth's surface) make it seem that with a theoretical asteroid 10 km big caused the crater great damage at the end of the Cretaceous (Alvarez et al. 1980).
There have been five well known extinctions on this earth. The one most well known is the mass extinction that ended the dinosaurs. Mass extinction is often described as the elimination of a large number of species in a short period of time. Despite what many think, the elimination of species is almost commonplace at this point. The Earth is currently in the middle of a sixth mass extinction, and it’s been caused by the human race.
Surprisingly, the clay held almost 30 times more iridium than the limestone layers above and below the clay. Similar layers in other parts of the world gave the same results. The conclusion was that a giant meteorite hit the Earth 65 million years ago and had released a large
Rapid climate change also ends up on the suspect list of possible dinosaur extinction events. During the latter part of the Cretaceous Period continents broke up causing volcanoes to erupt and fill the sky with gas and ash resulting in a drastic climate change (“Dinosaurs Climate Change and Biodiversity”). The shifting of continents changed the Earth’s landscape, altering weather patterns and overall climate (“Dinosaur Extinction Theories”). Also, over a long period of time, climate gradually changed. Ocean habits changed, temperatures grew much more extreme causing scorching summers and frigid winters (Norell, Dingus, and Gaffney). Radical temperature changes like these led to a green-house effect, making life for the dinosaurs a lot