K-T Extinction Outline

“A minority disputes this theory, arguing that other events-such as volcanic eruptions, sea-level changes or a series of impacts-were to blame for the spectacular loss of species that occurred at the transition between the Cretaceous and Tertiary periods…”

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.

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).

The Chicxulub crater is located on Mexico’s Yucatan peninsula and evaded detection for decades because it was buried while at the same time being reserved beneath a kilometre of younger rocks and sediments. Most scientists now agree that the Chicxulub crater is evidence that a huge asteroid or comet crashed into the Earth's surface 65 million years ago causing the extinction of more than 70% of the living species on the planet, including the dinosaurs. This collision idea was first popularised in 1980 by Luis Alvarez and his son, Walter Alvarez, where they developed the Alvarez hypothesis. They were studying a one centimetre-thick layer in Italy, which

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

In the two essays being discussed we learn that science has a vast range of definitions. Science is the effort to understand (or to understand better), the history of the natural world and how the natural world works with observable physical evidence as the base of understanding. Science is about how the hypothesis is developed and how well it is defended.

There have been five major mass extinction on earth triggered by a distinguishable event, but in The Sixth Extinction: An Unnatural History, Elizabeth Kolbert writes of the narrative of the sixth extinction caused directly by human impact. The book identifies the effects of human activity on how, over humans history on earth, the natural world has been affected. Every environmental impact stems into three basic groups of global problems to nature: Pollution, Habitat loss and Invasive Species. Kolbert explains that each impact can be traced back to one source, human industrial development. With each impact various types of life in the natural world are affected. Deforestation, urbanization, and sea level rise contribute to habitat loss worldwide. When humans began to travel they also brought invasive species and disease along with them; as boats only became bigger more and more invasive species travel. This reverse engineering of the planet species, brings new species that don’t have any natural predators, thus having an easier time driving native species out to endangerment or extinction. The different outcomes that come from human pollution is separated throughout the book, but the idea remains constant; with the development of human culture, pollution has drastically impacted a vast extent of species habitats and their environment.

There was much speculation regarding the K/T boundary being caused by a meteorite. The impact of this event was believed to have led to extended volcanic activity periods that in turn further polluted the atmosphere. The impact of the K-T boundary happened to be attributed to the extinction of dinosaurs that might have been as a result of new diseases. The impact affected all living things including primates. The impact is believed to have drastically slowed primate evolution (Clyde, 2010).

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.

According to Gould essay, the theory of disasters is “a large comet or asteroid struck the Earth some 65 million years ago, lofting a cloud of dust into the sky and blocking sunlight, thereby suppressing photosynthesis and so drastically lowering world temperatures that dinosaurs and hosts of other creatures became extinct.’(50).The theory of disasters proves worthy of more research when compared to the theory of sex and drugs. This is because the disasters theory “generates tests, provides us with things to do, and expands outward” (55). Cowell’s hypothesis (the theory of sex) “has generated nothing for 35 years” because scientists can do nothing with it and the theory of drugs “will win a few press nots and fade into oblivion (54-55). Although talking about asteroids, dust and darkness is no more entertaining than talking about fried testicles or terminal trips “it’s the iridium – the source of testable evidence – that counts and forges the crucial distinction between speculation and science.”(55).The iridium bridges the gap between science and speculation because it is a source of testable evidence. The iridium is testable because geologist determined when high iridium first formed and related it to the comet that struck the Earth. Therefore, the theory of disaster is the most superior evidence for dinosaur extinction when compared to the method of sex and drugs due to its abundant

of a rich Ir anomaly on a global scale within the K/T boundary layers of both marine and continental facies has been interpreted as highly impressive evidence for an impact origin. Another discovery that may serve as a marker of an event is microspherules. A variety of microsherules have been discovered in the PTB layers of the Meishan section (Xu et al., 1989). The origin of the microspherules could be multiple. They are small circular indentations in the rocks and the most abondent elements are Si or Si-Al. Mircospherules are similar to cosmic dust. Since a large amount of microspherules occurs in a thin layer of PTB layer it can serve as another event marker.<br><br>Maxwell (1989) who got his information from Clark et al. (1986) said that<br><br>The elemental in boundary clays across China suggest that there is a remote possibility that the predominantly illite boundary clay is a remote possibility that the predomonantly illite boundary clay resulted from the alteration of ejecta dust from a comet impact, but the most likely source was ash from a massive volcanic eruption.<br><br>The trace elements suggested that the dust was highly acidic and the ratios of TiO2 and AL2O3 are low enough to support the volcanic dust scenario

The Cretaceous period is a period of time within the Mesozoic Era lasting from 146 million years ago to 65.5 million years ago. It is one of three periods in the Mesozoic Era along with the Triassic and Jurassic periods. The Cretaceous period is well known for the amount of dinosaurs it had, and the event that put an end to the dinosaurs reign, the K-T mass extinction. During the K-T mass extinction, a huge asteroid hit earth and caused tons of dust to infiltrate the air. Only a small portion of dinosaurs died on impact Instead, the dust blocked out sunlight which caused plants to die. Without plants, many dinosaurs did not have a food source, so the died out. Carnivore dinosaurs, such as the Tyrannosaurus Rex, survived a little longer

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).

This final blow would have sent earth into a nuclear winter. According to this theory, dust caused by the asteroid collision disrupted plant growth by blocking out the sunlight needed for photosynthesis for nearly a year. A chain reaction occurred as plants died off, so did the herbivores relying on the plants, and then the carnivores that relied on the herbivores. Around 75% of species became extinct, including dinosaurs, mammals, giant marine lizards, fish, birds, and insects. Meanwhile, seawater flooded around 40% of the world’s continents ("Mass Extinctions").

These techniques led to the discovery of the boundary between the two eras. A single thin layer of clay found within predominantly limestone rocks established this. By comparing the marine life found in, above, and below the clay, the marine life, like the dinosaurs, had been terribly affected by the extinction event. The percentage of life in the upper layers was dramatically lower than that in the lower. This was far more compelling than what was suggested by dinosaur’s fossils.