The Cretaceous-Tertiary Extinction

The K-T or the Cretaceous-Tertiary extinction, was a mass extinction over unknown origin that took out an estimated 60-75 percent of all the species on earth 66 million years ago, most famously the dinosaurs. It was the end of the Cretaceous period and the Mesozoic Era and created the beginning of the Cenozoic Era that is still happening today. Geologically speaking this extinction happened in a very short amount of time. Although the most well known species to go extincted during this time was the dinosaurs there were also many other species that went during this time. On land many different types of mammals, one family of turtles, and plant life were effected by this event. Marine life like the plesiosaurs and the giant marine lizards went …show more content…
The three main hypothesis are volcanism, plate tectonics, and Alveres Hypothesis (extrinsic catastrophe). All of these hypothesis are backed by many different physical and geographical evidence. It is mentioned previously that there was long term global climatic change in the environment, in the volcanism hypothesis this is explained that over several million years the increased volcanic activity could have created enough soot and dust in the air that it blocked out the sunlight creating the cooler more varied climate that came with the Cenozoic Era. This seems like a very logical reasoning to why the climate would change but both the other hypothesis have a reasoning as well, the plate tectonics hypothesis suggest that there was a rearrangement of the continental plates that were occurring around the K-T boundary and this changed caused the water to recede from the land causing a less mild climate as the result. Where the Alveres hypothesis of an extrinsic catastrophe or extraterrestrial in nature catastrophe explains the long term climate change being the effect of the asteroids impact with the Earth causing enough dust to create the climate change. With the two hypothesis that support the long term climate change to be due to the fact that there was enough dust in the air to block out the sun they also explain that this would cause short term changes in the environment such …show more content…
All three of the hypothesis bring up good evidence that supports the long term climate change but the plate tectonics hypothesis does not support anything else. And while the other hypothesis support the reasoning behind the short term changes and the reasoning for the iridium found in the sediment layer of clay found at the boundaries both have there holes. While the Alverez Hypothesis has more evidence to support it than that of the volcanic eruptions neither hypothesis go into detail about why the extinctions of species was selective. Most of the hypothesis research behind the extinction of creatures on Earth focus on the dinosaurs alone. They do not explain why birds, who are a warm blooded creatures with high metabolic rates, and even though some smaller dinosaurs and larger bird species share ecological roles and terrestrial bipeds had survived while other species did not. Though both have unanswered questions in their hypothesis the Alverez hypothesis has more detailed explanations as to why the climate changed, why the sediment not only has iridium but also shock quartz, other physical evidence such as the found crater, and evidence with the line up of the time frames between the mass extinctions and when the Oort Clouds of Comets happen. Out of all the hypothesis the Alverez Hypothesis has the most evidence to back it up