The K-T Extinction event was triggered by a large scale asteroid impact that decimated the planet.

Approximately sixty-five million years ago, at the end of the Cretaceous period, an event occurred which decimated 90% of the species on the planet at the time. The main causes proposed for this event are the impact theory and the Alvarez theory, which are very similar. Most of the evidence used for these theories comes from the K-T Boundary. This Boundary is a line in the sedimentary rock in the Earth.

Various Viewpoints

In my research, I have discovered two different viewpoints about what could have happened to the dinosaurs sixty five million years ago.

Impact Theory

The impact theory suggests that the dinosaurs were decimated in an extraterrestrial impact. This impact has been calculated at being over 6 miles across, weighed 2 trillion tonnes, and hit the Earth with the force of 100 million megatons. Whilst travelling through the atmosphere the asteroid was transformed into a fireball and superheated the atmosphere. The impact of the asteroid caused a chain reaction of events:

• The impact of the asteroid sent boulders the size of buildings into the air which fell back to Earth as deadly projectiles at 100,000 miles per hour.
• Heat from the asteroid would have been hot enough to boil water in both plants and dinosaurs.
• The force of the impact sent shock waves into the planet and created an earthquake that would have measured 11.1 on the Richter scale.
• The blast pulse wave of the impact was faster than the speed of sound and could have ripped the skin off flesh.
• The force of the impact also sent 70 billion tonnes of pulverized stone and earth into the upper atmosphere creating an Ejector Cloud.
•  Friction within the cloud heated it to 15,000 degrees and baked the Earth
• A combination of an electrical storm and the heat of the Ejector Cloud ignited fires across the planet. The fires are thought to have reached 1,800 degrees and created winds. These fires moved at 9 miles per hour.
• The strain of the impact caused sedimentary rock to collapse under the sea which created a mega tsunami. The tsunami is estimated to have been 300 feet tall and hit 13,000 miles of coast line across the planet.
• Seismic shock waves that went through the planets core forced molten rock upwards resulting in massive volcanic eruptions. These eruptions added debris to the Ejector Cloud.
• The Ejector Cloud stopped heat and light from the sun reaching the Earth’s surface. This resulted in a nuclear winter and stopped photosynthesis throughout the planet.
• Hydrogen sulphide from the volcano rose into the water and the gases were released into the air. This particular gas paralyses the lungs and causes suffocation. 

Alvarez Hypothesis

Walter Alvarez, a geologist, and his son, Luis, a physicist, first detailed the impact theory associated with the Chicxulub crater in 1978. The Alvarez team analysed sediment found in the K-T layer of rock. The samples of sediment found in the layer showed an irregularly high concentration of iridium, an elemental substance that is rare on Earth, but found in large quantities in asteroids. Other samples from around the world were analysed and were found to have the same element. Using this data, they believed that an asteroid with a diameter of 6 miles (10 kilometres) would be needed to spread the iridium that far around the world. These discoveries lead the Alvarez team to conclude that an asteroid had impacted with the Earth about 65 million years ago and resulted in the mass extinction of the dinosaurs.

Keller Hypothesis

Gerta Keller, a palaeontologist, argues that the K-T Boundary was created 300,000 years before the extinction event occurred. The evidence found that supports this theory, in incredibly simple terms, is that, after examining samples of the rock above and beneath the K-T Boundary, Keller found that certain species of marine zooplankton on both sides of the boundary. This evidence led her to believe that the Chicxulub impact could not have been the cause for the extinction.

Conclusion

After extensive research into this topic, the most likely cause for the mass extinction of the dinosaurs sixty-five million years ago is the asteroid impact and it’s after affects. The impact itself was devastating to both the planet and the dinosaurs, however, it is the after affects that really killed off the dinosaurs. Although the evidence from Gerta Keller is compelling, it doesn’t seem to be entirely convincing. The Alvarez Hypothesis is supported by more evidence, and the evidence makes more sense than what Keller has offered.  

Reflection

Researching this topic was a lot harder than it was initially thought. Searching online library catalogues was hard, but actually going to the library and physically searching the shelves was much easier. Trying to find useful websites was the hardest part of the whole process. Most of the identified search terms weren’t useful in searching for websites or for books and DVDs. In the end, finding the online websites was a matter of searching for the words ‘dinosaur extinction’ and searching through the results.

Annotated Bibliography

Coffey, J. (2009) ‘Universe Today’. Asteroid Extinction Theory. [Online]. Available at <http://www.universetoday.com/36706/asteroid-extinction-theory/ > accessed 13 November 2011.

The article by Jerry Coffey is a useful source for beginners trying to understand the impact theory of dinosaur extinction. The article is very easy to read and understand. Although short, the article manages to go into a fair amount of detail about the event and the slight variations involved with the impact event theory.

Dixon, D. and Malam, J. (2006) Dinosaur. DK Publishing, New York.

Dinosaur was published by Dorling Kindersley, in conjunction with Google. The book gives an excellent overview of everything to do with dinosaurs, from what a dinosaur is to how and why a dinosaur is displayed in a museum. The section in the book on the mass extinction of the dinosaurs is brief yet succinct. The book is easy to understand as it is aimed at primary school children, yet the information is precise.

Last day of the dinosaurs. (2011) [Videorecording] Discovery Channel, Australia.

This Discovery Channel program interweaves a personal story into the subject of the extinction. The program gives the information about the asteroid impact within the story of several dinosaur species, and some individual ones. The program is a reliable source of information and is a useful source for anyone studying the dinosaur extinction event.

Palmer, D. (1999) The atlas of the prehistoric world. Marshall Publishing, London.

The Atlas to the Prehistoric World, published in association with the Discovery Channel, mainly focuses on the changing face of the planet over the millennia and how life has evolved. The book does contain some very insightful sections on the K-T Boundary and the physical impact from the asteroid. The text in the book is coupled with images that correlate well with the information and provide visual aids. The book is easy to understand for people in high school or higher.

Svarney, T. E.  and Svarney, P. B. (2003) The handy dinosaur answer book.  Visible Ink Press, London.

The Handy Dinosaur Answer Book is an excellent resource for studying dinosaurs. The book is split into several sections, covering topics including dinosaur anatomy, dinosaur behaviour and what happened to the dinosaurs. Each of these separate sections give their information in terms of the answer to a question that has been posed. The information is set out well and the information is easy to understand.

The Chicxulub Debate. (2004) [Internet]. Available at <http://geoweb.princeton.edu/people/faculty/keller/chicxpage1.html> accessed 24 October 2011.

The Chicxulub Debate is a paper written in 2004 by Gerta Keller, a leading palaeontologist based in America. The paper goes into great detail about her discoveries in relation to the Chicxulub crater and her theories about what happened when it occurred. The paper is very difficult to read and seems to repeat itself more than is necessary.