Why Did They Die Out?
Although scientists are still not completely convinced as to what lead to the extinction of the dinosaurs, they have made some substantial predictions. Theories have ranged from mass diseases to alien abduction!
Meteorite Impact
One of the most popular theories is actually a combination of several significant "sudden" catastrophes. There has been recorded evidence of a giant meteorite entering the atmosphere and landing near Yucatan Peninsula, Mexico about 65 million years ago. The size of this meteorite has been measured to be over 10km across in diameter. This impact would have been the same as 1000 bombs going off in one place at the same time! Scientists have found the element iridium at the surface of crater which is very unusual to find, yet common in meteorites. Obviously there would have been severe consequences for the rest of Earth.
Volcanic Eruptions
At the end of the Cretaceous period, the land formation had almost completed its move to the modern day configuration. This resulted in movement in the Earth's plates, producing volcanic activity. When volcanoes erupt, they propel dangerous gases and dust into the atmosphere. Some scientists believe that a large impact (such as a large meteorite hitting Earth) could jumpstart volcanic action. At the time of the suggested meteorite impact, India had enormous volcanic activity (half the continent is made up of lava flow). India and Yucatan were on exact opposite sides of the world. Scientists believe that the impact of a large meteorite could have sent shockwaves to the other side of the world, setting off volcanoes.
Extinction
If the above theories did actually occur, it would have been detrimental for the dinosaurs. The impact of the asteroid combined with volcanic action would have sent so much dust, gas and steam into the atmosphere that it would above blocked out the sun and poisoned the air. This would have lasted up to three months. As dinosaurs were very sensitive to change they would not have been able to survive. Food sources such as plants would have died out as the sun is very important to them. Without food they wouldn't have lasted long!
Without the sun, the temperature would have also dropped and cold-blooded dinosaurs would not have been able to regulate their body temperature.
Image by Ashley Year 6
Citations
Couch, S (1997) 101 Crazy Dinosaur Theories [internet] Available http://palaeo.gly.bris.ac.uk/Communication/Couch/Possible.html Accessed 19/02/2008
Dixon, D (2007) The World of the Dinosaurs. [book] Anness Publishing Ltd, London
Haines, T & Chambers, P (2006) The Complete Guide to Prehistoric Life. [book] Firefly Books, London
New Scientist (1997) What really killed the Dinosaurs [online article] Issue 2095, page 23, 16th August 1997 Available http://www.newscientist.com/channel/life/dinosaurs/mg15520954.700 Accessed 19/02/2008