The Many Theories on Dinosaurs Extinction

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While nobody really knows how dinosaurs became extinct there are six main theories. What killed the dinosaurs? How did dinosaurs go extinct.

Just how dinosaurs became extinct is a confusing thing to explain as not many people realize that not all the dinosaurs were alive at the same time, as such there was not one event that killed them all. There were several mass extinctions (at least five) that occurred at different times, marking the end of one period of time, and ushering in a new one. The final extinction event was 65 million years ago, and killed not only the dinosaurs, but most other life on the planet at that time.

There are many theories as to what caused these extinctions, and specifically the last dinosaur extinction, below are the six most likely scenarios in alphabetical order.

dinosaur in drumheller

photo by Author


The most commonly accepted theory is an Asteroid impacted the earth in the area that is now the Gulf of Mexico. This is often referred to as the KT Asteroid, and the result of a roughly 6 mile wide (10 km) asteroid hitting the earth would have caused massive problems for life on the planet. The sun would have been obscured by dust particles for months, thus killing plants and the animals that ate them, in turn animals who fed on those animals would have perished. The impact would have also resulted in tidal waves, acid rain, and probably forest fires. Water would have been tainted with falling particles, and survival of many animals would come to a halt. Evidence for the asteroid impact has been found in the form of a layer of sediment which has turned up all over the globe in earth layers from the same time period. Perhaps other asteroids were linked to earlier periods of extinction.

Climate Change

As the Cretaceous period came to a close we saw mostly tropical plants, with the Tertiary period plant life had changed. Global temperature fluctuations were beginning to occur and some animals just could not keep up. Certain plants would have died, and plant eaters would have been left without food, then too would the meat eaters. Indeed plankton have been shown to have decreased in numbers around this time, clearly cutting the food supply of marine animals. One interesting not about the climate change theory is that it not only allowed for the survival of the furry mammals, but possibly the survival of a few species of dinosaurs whose bodies had been experimenting with the development of feathers. Imagine if this was enough to keep them warm enough to survive the temperature fluctuations and enable them to continue evolving possibly into birds.

did dinosaurs evolve into chickens

Picture by Author


If some sort of disease, or plague, were to take hold it could wipe out a species in a few years. In the case of the dinosaurs the disease would have to be one that was not species specific, or could have been one that destroyed plants. Fewer plants means less food for the plant eaters, with them gone, meat eaters would also die. The disease theory may be held responsible for some smaller die offs, but probably did not cause any of the major extinctions.  This theory is still in play but not considered as valuable as the others. 


One theory is that early mammals were responsible for eating dinosaur eggs, thus ending their ability to reproduce effectively. This theory has been all but discounted as we know some dinosaurs guarded their nests, and it does not account for the extinction of the marine life that also occurred at the time.

Oxygen Levels

This is a relatively new theory and gaining more support.  During the reign of the dinosaurs oxygen levels were higher they are today. We know this because air bubbles have been found in fossilized amber. These higher oxygen levels have been recently cited as a contributing factor for allowing the dinosaurs to grow to their massive sizes. As the continental plates broke up volcanic activity was responsible for changing the levels of oxygen to what they are today. As such many animals would have found continued survival impossible.

Volcanic Activity

Volcanic activity was at a high and surely there would have been noticeable consequences for life at the time, but could volcanoes cause enough damage to wipe out entire species? They would have to create enough debris in the air to block the sun from reaching the plants thus interrupting the food chain. This would have had to occur on a global scale so would require several volcanoes erupting withing a few months of each other. Although volcanoes might have played a role this way, it is more likely they are linked to the changes in the oxygen level as mentioned above.


We know that there were survivors of every mass extinction, only certain species were entirely wiped out. These animals either are known today as “living fossils” or they evolved into new animals. Some examples of the survivors are turtles and snails, others who have evolved since are sharks, and even more so mammals. Birds are likely the result of some surviving dinosaurs in combination with natural evolution since the last big extinction.

As a note of interest, scientists have also discovered a sixth extinction event.  One that is going on in our current times.  They have termed this extinction event as The Holocene Extinction Event.  The cause?  Humans.

If you enjoy reading about Dinosaurs you will also like this link on an early mistake made by Dinosaur hunters.

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Felisa Daskeo
Posted on Mar 6, 2010
Glynis Smy
Posted on Feb 21, 2010