Abstract
This paper takes a look at the Permian and Cretaceous-Tertiary periods of life on Earth - pre-historic forms of life from sea creatures to land and air creatures. During both of these periods, mass extinction occurred and a comparison of these two extinctions is documented in this paper.

From the paper:

"From the perspective of daily human life, we often think of tragedy on the level of individual death and destruction, and the concept of mass extinction as being confined to a species or at worst, an ecosystem. However, over the course of the existence of the earth, the planet has weathered many greater catastrophes. Geologists must take a much longer-term perspective of catastrophe when studying extinction. This paper will compare and contrast the Permian and Cretaceous-Tertiary mass extinctions."

Tags:dinosaur, marine, reptile, amphibian, ocean, terrestrial, nature, organic, volcanoe, demise

Abstract
This paper attempts to prove why the impact theory is the most plausible reasoning behind the mass extinction that wiped out the dinosaurs and so many other species at the K-T boundary. By looking at the substantial amount of evidence for this theory, it examines how the impact theory as opposed to the volcanic theory is currently the most valid explanation for understanding why so many of the world's plants and animals died out at the end of the Cretaceous period.
Outline
What's in a Theory: The History of Mass Extinction Hypotheses
The K-T Boundary: The Cold, Hard Facts
The Impact Theory
The Volcanism Theory
Which is More Plausible?
Conclusion

From the Paper
"As the years progressed and theories for mass extinction began to multiply, the concepts of catastrophism and uniformitarianism were born. Catastrophism is, "the doctrine that major changes in the Earth's crust result from catastrophes rather than evolutionary processes" (Catastrophism). In this definition, "catastrophes" include anything that cannot be explained by solid, proven, unwavering geological processes visible on the Earth. A flood of the magnitude recounted in the Bible would mean that the geological process of the water cycle would have to be sped up tremendously. This is a perfect example of catastrophism because at the time in which it was most widely-accepted, it was perfectly acceptable to society that the Flood was a largely disastrous event brought upon the Earth by God, and not a constant geological process such as weathering or volcanic activity."

Tags:geology, meteor, cretaceous, k-t, boundary, tektites

Abstract
This paper defines what is meant by mass extinction and discusses a few that have occurred on our planet and some of the theories that have attempted to explain them. The writer explains that while some believe in meteorites or comet showers, and others in volcanism, variations in sea level, global climate changes and changes in ocean levels of oxygen, still a third group of scientists believe it was likely a combination of two or more of these events. The paper concludes that it is still unclear exactly what caused mass extinctions, and because of the elapsed time it is doubtful that we will ever know for sure.

From the Paper
"Most of us are, of course most familiar with the extinction of the dinosaurs. Practically every child is fascinated by these huge beasts that roamed our planet at one time and now do not exist at all. In 1979 Berkeley scientists discovered a piece of pink and white limestone which contained evidence of what the scientists called "the great dying." (Rogers 1). The rock was found near Gubbio, Italy, and was at one time under the sea. To make an involved story short, the Cretaceous limestone has many fossils of tiny crustaceans while these little crustacean fossils are entirely absent from the clay layer, reappearing again in the Tertiary limestone. The scientist measured the presence of iridium, and found a substantial increase in the clay--twenty five times more than normal."

Tags:marine, comet, ecological, asteroid, Cretaceous, extraterrestrial, volcanism

Abstract
This paper looks at the numerous theories that have been presented over time regarding the reason for dinosaur extinction. The author discusses explanations such as a sudden catastrophic event, like a meteor hitting the earth or a volcanic eruption, and also slow, environmental causes like global warming or shifting plate tectonics.

From the Paper
"First, around the time of the mass extinction of the dinosaurs there was a global climate change. During this time, the environment changed from the warm and mild one present in the Mesozoic era to the cooler one of the Cenozoic. Second, evidence exists to support a massive terrestrial disturbance at the end of the Cretaceous period that included soot in the air, acid rain, the emission of poisonous gases, and a cooling similar to that of a nuclear winter. This terrestrial disturbance caused periods of darkness on the earth as well as a global greenhouse effect. Third, the dinosaurs were only one species that became extinct during this time. According to scientific evidence, approximately 60 percent of all species below the line of the K-T boundary did not exist above that line."

Tags:earth, sudden, impact, environment, volcano, meteor, era, period, mesozoic, cretaceous, k-t, boundary, evidence, science, decline, global, cause